From 80bccc912f70ca38d3c994b4b22b2025357af565 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 14:46:03 +0200
Subject: [PATCH 01/25] Add some primitive Emscripten support, based on WASI

---
 driver/main.cpp                            |  6 ++--
 driver/tool.cpp                            |  2 ++
 runtime/CMakeLists.txt                     |  4 +++
 runtime/druntime/src/core/sys/posix/time.d | 41 ++++++++++++++++++++++
 tests/codegen/emscripten.d                 |  5 +--
 5 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/driver/main.cpp b/driver/main.cpp
index 89475c50bd2..55954d834ab 100644
--- a/driver/main.cpp
+++ b/driver/main.cpp
@@ -960,10 +960,10 @@ void registerPredefinedTargetVersions() {
 #endif
   case llvm::Triple::Emscripten:
     VersionCondition::addPredefinedGlobalIdent("Emscripten");
-    // Emscripten uses musl and libc++, so mimic a musl Linux platform:
-    VersionCondition::addPredefinedGlobalIdent("linux");
+    VersionCondition::addPredefinedGlobalIdent("WASI");
+    VersionCondition::addPredefinedGlobalIdent("WASIp1");
     VersionCondition::addPredefinedGlobalIdent("Posix");
-    VersionCondition::addPredefinedGlobalIdent("CRuntime_Musl");
+    VersionCondition::addPredefinedGlobalIdent("CRuntime_WASI");
     VersionCondition::addPredefinedGlobalIdent("CppRuntime_LLVM");
     VersionCondition::addPredefinedGlobalIdent("CppRuntime_Clang"); // legacy
     break;
diff --git a/driver/tool.cpp b/driver/tool.cpp
index 5a5666ccc9c..158e2480df0 100644
--- a/driver/tool.cpp
+++ b/driver/tool.cpp
@@ -96,6 +96,8 @@ llvm::SmallVector<std::string, 2> findCCFallback() {
       choices = {{"wasm32-wasi-clang"}};
       break;
     }
+  } else if (triple.isOSEmscripten()) {
+    choices = { { "emcc" } };
   } else {
     choices = {
       { opts::mTargetTriple + "-gcc" },
diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 63efdb03b4a..9e65a6b1478 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -104,6 +104,10 @@ if("${TARGET_SYSTEM}" MATCHES "WASI|Emscripten")
 
     append("-Wl,-z,stack-size=1048576 -Wl,--stack-first" LD_FLAGS)
 
+    if("${TARGET_SYSTEM}" MATCHES "Emscripten")
+        append("-sALLOW_MEMORY_GROWTH" LD_FLAGS)
+    endif()
+
     list(APPEND D_FLAGS --wasm-enable-eh)
     if(LLVM_VERSION_MAJOR GREATER_EQUAL 20)
         list(APPEND D_FLAGS --wasm-use-legacy-eh=false)
diff --git a/runtime/druntime/src/core/sys/posix/time.d b/runtime/druntime/src/core/sys/posix/time.d
index c90ac45bcab..aad88d35ece 100644
--- a/runtime/druntime/src/core/sys/posix/time.d
+++ b/runtime/druntime/src/core/sys/posix/time.d
@@ -164,6 +164,10 @@ else version (Solaris)
 {
     enum CLOCK_MONOTONIC = 4;
 }
+else version (Emscripten)
+{
+    enum CLOCK_MONOTONIC = 1;
+}
 else version (CRuntime_WASI)
 {
     struct __clockid;
@@ -539,6 +543,43 @@ else version (CRuntime_Musl)
     int timer_settime(timer_t, int, const scope itimerspec*, itimerspec*);
     int timer_getoverrun(timer_t);
 }
+else version (Emscripten)
+{
+    alias clockid_t = int;
+    alias timer_t = void*;
+
+    struct itimerspec
+    {
+        timespec it_interval;
+        timespec it_value;
+    }
+
+    enum TIMER_ABSTIME = 1;
+
+    enum CLOCK_REALTIME = 0;
+    enum CLOCK_PROCESS_CPUTIME_ID = 2;
+    enum CLOCK_THREAD_CPUTIME_ID = 3;
+    enum CLOCK_REALTIME_COARSE = 5;
+    enum CLOCK_BOOTTIME = 7;
+    enum CLOCK_REALTIME_ALARM = 8;
+    enum CLOCK_BOOTTIME_ALARM = 9;
+    enum CLOCK_SGI_CYCLE = 10;
+    enum CLOCK_TAI = 11;
+
+    int nanosleep(const scope timespec*, timespec*);
+
+    int clock_getres(clockid_t, timespec*);
+    int clock_gettime(clockid_t, timespec*);
+    int clock_settime(clockid_t, const scope timespec*);
+    int clock_nanosleep(clockid_t, int, const scope timespec*, timespec*);
+    int clock_getcpuclockid(pid_t, clockid_t *);
+
+    //int timer_create(clockid_t, sigevent*, timer_t*);
+    int timer_delete(timer_t);
+    int timer_gettime(timer_t, itimerspec*);
+    int timer_settime(timer_t, int, const scope itimerspec*, itimerspec*);
+    int timer_getoverrun(timer_t);
+}
 else version (CRuntime_WASI)
 {
     alias clockid_t = const __clockid*;
diff --git a/tests/codegen/emscripten.d b/tests/codegen/emscripten.d
index 74505912e59..cf72136bc3f 100644
--- a/tests/codegen/emscripten.d
+++ b/tests/codegen/emscripten.d
@@ -7,9 +7,10 @@
 // test predefined versions:
 
 version (Emscripten) {} else static assert(0);
-version (linux) {} else static assert(0);
+version (WASI) {} else static assert(0);
+version (WASIp1) {} else static assert(0);
 version (Posix) {} else static assert(0);
-version (CRuntime_Musl) {} else static assert(0);
+version (CRuntime_WASI) {} else static assert(0);
 version (CppRuntime_LLVM) {} else static assert(0);
 
 

From e5da7df8b9251712e5de57403bb144bc784da71c Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 15:00:32 +0200
Subject: [PATCH 02/25] CI: Add Emscripten job

---
 .../actions/1a-setup-emscripten/action.yml    | 18 +++++++++
 .github/actions/5a-emscripten/action.yml      | 37 +++++++++++++++++++
 .github/workflows/main.yml                    | 20 +++++++++-
 3 files changed, 73 insertions(+), 2 deletions(-)
 create mode 100644 .github/actions/1a-setup-emscripten/action.yml
 create mode 100644 .github/actions/5a-emscripten/action.yml

diff --git a/.github/actions/1a-setup-emscripten/action.yml b/.github/actions/1a-setup-emscripten/action.yml
new file mode 100644
index 00000000000..4d7a76d5360
--- /dev/null
+++ b/.github/actions/1a-setup-emscripten/action.yml
@@ -0,0 +1,18 @@
+name: "Emscripten: Install additional prerequisites"
+inputs:
+  emsdk_version:
+    required: false
+    default: '6.0.6'
+runs:
+  using: composite
+  steps:
+    - name: "Install emsdk" # into ../emsdk
+      shell: bash
+      run: |
+        set -eux
+        cd ..
+
+        git clone https://github.com/emscripten-core/emsdk.git
+        cd emsdk
+        ./emsdk install '${{ inputs.emsdk_version }}'
+        ./emsdk activate '${{ inputs.emsdk_version }}'
diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
new file mode 100644
index 00000000000..c8f011f46b5
--- /dev/null
+++ b/.github/actions/5a-emscripten/action.yml
@@ -0,0 +1,37 @@
+name: "Emscripten: Cross-compile druntime incl. test runners, install libs + .conf, run druntime unittests"
+inputs:
+  arch:
+    required: true
+runs:
+  using: composite
+  steps:
+    - name: Cross-compile druntime incl. test runners & install libs + .conf
+      shell: bash
+      run: |
+        set -eux
+        cd ..
+
+        os='emscripten'
+        arch='${{ inputs.arch }}'
+        triple="$arch-unknown-$os"
+
+        bootstrap-ldc/bin/ldc-build-runtime \
+          --ninja \
+          --dFlags="-mtriple=$triple" \
+          --ldcSrcDir="$PWD/ldc" \
+          --installWithSuffix="-$os-$arch" \
+          --testrunners \
+          CMAKE_INSTALL_PREFIX="$PWD/install" \
+          RT_CONF_TRIPLE_REGEX="$arch-.*-$os" \
+          CMAKE_TOOLCHAIN_FILE="$PWD/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake" \
+          PHOBOS2_DIR="" \
+          BUILD_LTO_LIBS=ON
+
+    - name: Run druntime unittests
+      shell: bash
+      run: |
+        set -eux
+        cd ../ldc-build-runtime.tmp
+
+        ../emsdk/node/*/bin/node ./druntime-test-runner-debug.js
+        ../emsdk/node/*/bin/node ./druntime-test-runner.js
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index dd998f011fc..c6e1dbe05f5 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -387,6 +387,10 @@ jobs:
       matrix:
         include:
           - job_name: WASI wasm32
+            os: wasi
+            arch: wasm32
+          - job_name: Emscripten wasm32
+            os: emscripten
             arch: wasm32
     name: ${{ matrix.job_name }}
     runs-on: ubuntu-22.04-arm
@@ -404,28 +408,40 @@ jobs:
           clang_major: ${{ env.CLANG_MAJOR }}
           arch: aarch64
       - name: 'WASI: Install additional prerequisites'
+        if: matrix.os == 'wasi'
         uses: ./.github/actions/1a-setup-wasi
+      - name: 'Emscripten: Install additional prerequisites'
+        if: matrix.os == 'emscripten'
+        uses: ./.github/actions/1a-setup-emscripten
       - name: Build bootstrap LDC
         uses: ./.github/actions/2-build-bootstrap
       - name: 'WASIp1: Cross-compile druntime & phobos incl. test runners & run druntime & phobos unittests'
+        if: matrix.os == 'wasi'
         uses: ./.github/actions/5a-wasi
         with:
           os: wasip1
           arch: ${{ matrix.arch }}
       - name: 'WASIp2: Cross-compile druntime & phobos incl. test runners & run druntime & phobos unittests'
+        if: matrix.os == 'wasi'
         uses: ./.github/actions/5a-wasi
         with:
           os: wasip2
           arch: ${{ matrix.arch }}
+      - name: 'Emscripten: Cross-compile druntime incl. test runners & run druntime unittests'
+        if: matrix.os == 'emscripten'
+        uses: ./.github/actions/5a-emscripten
+        with:
+          arch: ${{ matrix.arch }}
       - name: Make installed .conf files portable
         uses: ./.github/actions/5b-make-portable
       - name: Create addon package & upload artifact
         uses: ./.github/actions/7-package
         with:
           arch: ${{ matrix.arch }}
-          os: wasi
+          os: ${{ matrix.os }}
           is_addon: true
-      - name: Smoke-test add-on package
+      - name: 'WASI: Smoke-test add-on package'
+        if: matrix.os == 'wasi'
         run: |
           set -eux
           # unpack addon archive into ../bootstrap-ldc

From 1f50a082aca11f9c3b96338f3d5faa20017be04f Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 15:55:10 +0200
Subject: [PATCH 03/25] [try building Phobos too]

---
 .github/actions/5a-emscripten/action.yml | 5 ++---
 .github/workflows/main.yml               | 2 +-
 runtime/phobos                           | 2 +-
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index c8f011f46b5..0b8b691c95e 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -1,11 +1,11 @@
-name: "Emscripten: Cross-compile druntime incl. test runners, install libs + .conf, run druntime unittests"
+name: "Emscripten: Cross-compile druntime & phobos incl. test runners, install libs + .conf, run druntime unittests"
 inputs:
   arch:
     required: true
 runs:
   using: composite
   steps:
-    - name: Cross-compile druntime incl. test runners & install libs + .conf
+    - name: Cross-compile druntime & phobos incl. test runners & install libs + .conf
       shell: bash
       run: |
         set -eux
@@ -24,7 +24,6 @@ runs:
           CMAKE_INSTALL_PREFIX="$PWD/install" \
           RT_CONF_TRIPLE_REGEX="$arch-.*-$os" \
           CMAKE_TOOLCHAIN_FILE="$PWD/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake" \
-          PHOBOS2_DIR="" \
           BUILD_LTO_LIBS=ON
 
     - name: Run druntime unittests
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index c6e1dbe05f5..3a0ffa0e99d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -427,7 +427,7 @@ jobs:
         with:
           os: wasip2
           arch: ${{ matrix.arch }}
-      - name: 'Emscripten: Cross-compile druntime incl. test runners & run druntime unittests'
+      - name: 'Emscripten: Cross-compile druntime & phobos incl. test runners & run druntime unittests'
         if: matrix.os == 'emscripten'
         uses: ./.github/actions/5a-emscripten
         with:
diff --git a/runtime/phobos b/runtime/phobos
index 8017f195c44..7b79b4a1c9e 160000
--- a/runtime/phobos
+++ b/runtime/phobos
@@ -1 +1 @@
-Subproject commit 8017f195c44ce6dd7f883489b7b12f33dac66c45
+Subproject commit 7b79b4a1c9e6ad2164f016c7789d39bc915f6fba

From 9ed081277599da169908181fbc98f7d609a69b36 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 16:38:12 +0200
Subject: [PATCH 04/25] [ignore unittest failures, and try running the Phobos
 debug testrunner too]

---
 .github/actions/5a-emscripten/action.yml | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 0b8b691c95e..5fa0d649d75 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -32,5 +32,13 @@ runs:
         set -eux
         cd ../ldc-build-runtime.tmp
 
-        ../emsdk/node/*/bin/node ./druntime-test-runner-debug.js
-        ../emsdk/node/*/bin/node ./druntime-test-runner.js
+        ../emsdk/node/*/bin/node ./druntime-test-runner-debug.js || true
+        ../emsdk/node/*/bin/node ./druntime-test-runner.js || true
+
+    - name: Run phobos unittests
+      shell: bash
+      run: |
+        set -eux
+        cd ../ldc-build-runtime.tmp
+
+        ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true

From a4e9abd70f3d9327657b3f9c58d93e366da67293 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 17:28:00 +0200
Subject: [PATCH 05/25] [fix linking with emcc]

---
 driver/linker-gcc.cpp | 23 ++++++++++++-----------
 driver/linker.cpp     |  5 ++---
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/driver/linker-gcc.cpp b/driver/linker-gcc.cpp
index 11320083e51..98c8b4e7465 100644
--- a/driver/linker-gcc.cpp
+++ b/driver/linker-gcc.cpp
@@ -635,6 +635,8 @@ void ArgsBuilder::addLinker() {
 //////////////////////////////////////////////////////////////////////////////
 
 void ArgsBuilder::addUserSwitches() {
+  const bool isEmcc = global.params.targetTriple->isOSEmscripten();
+
   // additional linker and cc switches (preserve order across both lists)
   for (unsigned ilink = 0, icc = 0;;) {
     unsigned linkpos = ilink < opts::linkerSwitches.size()
@@ -654,7 +656,14 @@ void ArgsBuilder::addUserSwitches() {
       if (!(str.starts_with("-l") || str.starts_with("-L") ||
             str.starts_with("-Wl,") || str.starts_with("-shared") ||
             str.starts_with("-static"))) {
-        args.push_back("-Xlinker");
+        // avoid `-Xlinker <p>` for Emscripten's emcc, seems buggy; use
+        // `-Wl,<p>` instead
+        if (isEmcc) {
+          args.push_back("-Wl," + p);
+          continue;
+        } else {
+          args.push_back("-Xlinker");
+        }
       }
       args.push_back(p);
     } else if (ccpos < linkpos) {
@@ -807,16 +816,8 @@ int linkObjToBinaryGcc(llvm::StringRef outputPath,
 #endif
 
   // build command-line for gcc-compatible linker driver
-  // exception: invoke (ld-compatible) linker directly for WebAssembly targets
-  std::string tool;
-  std::unique_ptr<ArgsBuilder> argsBuilder;
-  if (global.params.targetTriple->isOSBinFormatWasm() && !global.params.targetTriple->isOSWASI()) {
-    argsBuilder = std::make_unique<LdArgsBuilder>();
-    tool = getProgram("wasm-ld", &opts::linker);
-  } else {
-    argsBuilder = std::make_unique<ArgsBuilder>();
-    tool = getCC(argsBuilder->args);
-  }
+  auto argsBuilder = std::make_unique<ArgsBuilder>();
+  std::string tool = getCC(argsBuilder->args);
 
   // build arguments
   argsBuilder->build(outputPath, defaultLibNames);
diff --git a/driver/linker.cpp b/driver/linker.cpp
index 6f5cccd28ec..6774adcddec 100644
--- a/driver/linker.cpp
+++ b/driver/linker.cpp
@@ -103,9 +103,8 @@ static std::string getOutputPath() {
     extension = target.dll_ext.ptr;
   } else if (triple.isOSWindows()) {
     extension = "exe";
-  } else if (triple.getArch() == llvm::Triple::wasm32 ||
-             triple.getArch() == llvm::Triple::wasm64) {
-    extension = "wasm";
+  } else if (triple.isWasm()) {
+    extension = triple.isOSEmscripten() ? "js" : "wasm";
   }
 
   if (global.params.exefile.length) {

From f75de5eb9144d39c056d94a6b6c1e59d337460d0 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 17:36:18 +0200
Subject: [PATCH 06/25] [enable addon-package smoke test for Emscripten too]

---
 .github/workflows/main.yml | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3a0ffa0e99d..e214b33616a 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -440,8 +440,7 @@ jobs:
           arch: ${{ matrix.arch }}
           os: ${{ matrix.os }}
           is_addon: true
-      - name: 'WASI: Smoke-test add-on package'
-        if: matrix.os == 'wasi'
+      - name: 'Smoke-test add-on package'
         run: |
           set -eux
           # unpack addon archive into ../bootstrap-ldc
@@ -449,17 +448,29 @@ jobs:
           tar xf ${{ github.workspace }}/artifacts/*-addon-*.tar.xz
           # generate hello.d
           echo 'void main() { import std.stdio; writefln!"Hello world, %d bits"(size_t.sizeof * 8); }' > hello.d
-          # put WASI-SDK clang onto PATH
-          export PATH="$PWD/../wasi-sdk/bin:$PATH"
-          # build & run hello-world
-          for os in wasip1 wasip2; do
-            # test LTO too
+
+          if [[ '${{ matrix.os }}' == wasi ]]; then
+            # put WASI-SDK clang onto PATH
+            export PATH="$PWD/../wasi-sdk/bin:$PATH"
+            # build & run hello-world
+            for os in wasip1 wasip2; do
+              # test LTO too
+              for args in "" "-O -flto=full -defaultlib=druntime-ldc-lto,phobos2-ldc-lto"; do
+                bin/ldc2 -mtriple=${{ matrix.arch }}-unknown-$os $args hello.d
+                ls -l hello.wasm
+                ../wasmtime/wasmtime -W exceptions ./hello.wasm
+              done
+            done
+          elif [[ '${{ matrix.os }}' == emscripten ]]; then
+            # put emcc onto PATH
+            export PATH="$PWD/../emsdk/upstream/emscripten:$PATH"
+            # build & run hello-world
             for args in "" "-O -flto=full -defaultlib=druntime-ldc-lto,phobos2-ldc-lto"; do
-              bin/ldc2 -mtriple=${{ matrix.arch }}-unknown-$os $args hello.d
-              ls -l hello.wasm
-              ../wasmtime/wasmtime -W exceptions ./hello.wasm
+              bin/ldc2 -mtriple=${{ matrix.arch }}-unknown-emscripten $args hello.d
+              ls -l hello.{js,wasm}
+              ../emsdk/node/*/bin/node ./hello.js
             done
-          done
+          fi
 
 
   merge-macos:

From a825d0cd29b9e4d71119bcdc71d4aaac03821cb3 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 18:03:20 +0200
Subject: [PATCH 07/25] [add importc_compare test]

---
 .github/actions/5a-emscripten/action.yml | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 5fa0d649d75..08c7c3133da 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -42,3 +42,25 @@ runs:
         cd ../ldc-build-runtime.tmp
 
         ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true
+
+    - name: Run `importc_compare`
+      shell: bash
+      run: |
+        set -eux
+        cd ..
+
+        os='emscripten'
+        arch='${{ inputs.arch }}'
+        triple="$arch-unknown-$os"
+
+        bootstrap-ldc/bin/ldc2 \
+          -defaultlib=druntime-ldc -L-Linstall/lib-$os-$arch \
+          -gcc="$PWD/emsdk/upstream/emscripten/emcc" \
+          --mtriple=$triple \
+          --d-version=WASI_EMULATED_SIGNAL \
+          --d-version=WASI_EMULATED_PROCESS_CLOCKS \
+          --d-version=WASI_EMULATED_MMAN \
+          -I$PWD/ldc/runtime/druntime/test/importc_compare/src \
+          $PWD/ldc/runtime/druntime/test/importc_compare/src/importc_compare.d
+
+        emsdk/node/*/bin/node ./importc_compare.js || true

From 834c6d1c89d3ab1939395dec7a7233a670ddb0b8 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Mon, 10 Aug 2026 19:54:20 +0200
Subject: [PATCH 08/25] [druntime: Fix some issues reported by importc_compare]

---
 runtime/druntime/src/core/stdc/fenv.d         |  9 +++++
 runtime/druntime/src/core/sys/posix/dirent.d  | 11 ++++++
 .../druntime/src/core/sys/posix/netinet/in_.d | 11 ++++--
 runtime/druntime/src/core/sys/posix/signal.d  | 25 +++++++++++++
 .../druntime/src/core/sys/posix/stdc/time.d   | 19 +++++++++-
 .../src/core/sys/posix/sys/resource.d         | 29 +++++++++++++++
 .../druntime/src/core/sys/posix/sys/socket.d  | 36 ++++++++++++++-----
 runtime/druntime/src/core/sys/posix/sys/un.d  |  8 +++++
 8 files changed, 136 insertions(+), 12 deletions(-)

diff --git a/runtime/druntime/src/core/stdc/fenv.d b/runtime/druntime/src/core/stdc/fenv.d
index 4e4b0317aa6..9708fc62c86 100644
--- a/runtime/druntime/src/core/stdc/fenv.d
+++ b/runtime/druntime/src/core/stdc/fenv.d
@@ -450,6 +450,15 @@ else version (CRuntime_Musl)
         static assert(false, "Architecture not supported.");
     }
 }
+else version (Emscripten)
+{
+    struct fenv_t
+    {
+        uint __cw;
+    }
+
+    alias fexcept_t = ushort;
+}
 else version (CRuntime_WASI)
 {
     import core.stdc.config : c_ulong;
diff --git a/runtime/druntime/src/core/sys/posix/dirent.d b/runtime/druntime/src/core/sys/posix/dirent.d
index 868e8fba246..20cd54c434b 100644
--- a/runtime/druntime/src/core/sys/posix/dirent.d
+++ b/runtime/druntime/src/core/sys/posix/dirent.d
@@ -158,6 +158,17 @@ else version (Solaris)
         char[1] d_name = 0;
     }
 }
+else version (Emscripten)
+{
+    struct dirent
+    {
+        ino_t d_ino;
+        off_t d_off;
+        ushort d_reclen;
+        ubyte d_type;
+        char[256] d_name = 0;
+    }
+}
 else version (CRuntime_WASI)
 {
     struct dirent
diff --git a/runtime/druntime/src/core/sys/posix/netinet/in_.d b/runtime/druntime/src/core/sys/posix/netinet/in_.d
index 276bddd8181..374d762c4b3 100644
--- a/runtime/druntime/src/core/sys/posix/netinet/in_.d
+++ b/runtime/druntime/src/core/sys/posix/netinet/in_.d
@@ -1631,8 +1631,15 @@ else version (CRuntime_WASI)
         ubyte[16] s6_addr;
     }
     struct sockaddr_in6 {
-        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-        sa_family_t     sin6_family;
+        version (Emscripten) // no alignment override
+        {
+            sa_family_t     sin6_family;
+        }
+        else
+        {
+            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+            sa_family_t     sin6_family;
+        }
 
         in_port_t       sin6_port;
         uint            sin6_flowinfo;
diff --git a/runtime/druntime/src/core/sys/posix/signal.d b/runtime/druntime/src/core/sys/posix/signal.d
index 76ba404e5c7..9ebf39f982f 100644
--- a/runtime/druntime/src/core/sys/posix/signal.d
+++ b/runtime/druntime/src/core/sys/posix/signal.d
@@ -1484,6 +1484,31 @@ else version (Solaris)
     enum SI_ASYNCIO = -4;
     enum SI_MESGQ   = -5;
 }
+else version (Emscripten)
+{
+    struct sigset_t
+    {
+        c_ulong[2] __bits;
+
+    }
+
+    enum SIG_BLOCK      = 0;
+    enum SIG_UNBLOCK    = 1;
+    enum SIG_SETMASK    = 2;
+
+    enum
+    {
+        SI_ASYNCNL = -60,
+        SI_TKILL   = -6,
+        SI_SIGIO,
+        SI_ASYNCIO,
+        SI_MESGQ,
+        SI_TIMER,
+        SI_QUEUE,
+        SI_USER,
+        SI_KERNEL  = 0x80
+    }
+}
 else version (CRuntime_WASI)
 {
     alias sigset_t = ubyte;
diff --git a/runtime/druntime/src/core/sys/posix/stdc/time.d b/runtime/druntime/src/core/sys/posix/stdc/time.d
index 3278751f591..8adad1b2594 100644
--- a/runtime/druntime/src/core/sys/posix/stdc/time.d
+++ b/runtime/druntime/src/core/sys/posix/stdc/time.d
@@ -34,7 +34,24 @@ nothrow:
 @nogc:
 
 ///
-version (CRuntime_WASI)
+version (Emscripten)
+{
+    struct tm
+    {
+        int     tm_sec;     /// seconds after the minute [0-60]
+        int     tm_min;     /// minutes after the hour [0-59]
+        int     tm_hour;    /// hours since midnight [0-23]
+        int     tm_mday;    /// day of the month [1-31]
+        int     tm_mon;     /// months since January [0-11]
+        int     tm_year;    /// years since 1900
+        int     tm_wday;    /// days since Sunday [0-6]
+        int     tm_yday;    /// days since January 1 [0-365]
+        int     tm_isdst;   /// Daylight Savings Time flag
+        c_long  tm_gmtoff;  /// offset from CUT in seconds
+        char*   tm_zone;    /// timezone abbreviation
+    }
+}
+else version (CRuntime_WASI)
 {
     struct tm
     {
diff --git a/runtime/druntime/src/core/sys/posix/sys/resource.d b/runtime/druntime/src/core/sys/posix/sys/resource.d
index 62d3e05d9f9..b147fced256 100644
--- a/runtime/druntime/src/core/sys/posix/sys/resource.d
+++ b/runtime/druntime/src/core/sys/posix/sys/resource.d
@@ -496,6 +496,35 @@ else version (Solaris)
         RLIMIT_AS     = 6,
     }
 }
+else version (Emscripten)
+{
+    struct rusage
+    {
+        timeval ru_utime;
+        timeval ru_stime;
+        c_long ru_maxrss;
+        c_long ru_ixrss;
+        c_long ru_idrss;
+        c_long ru_isrss;
+        c_long ru_minflt;
+        c_long ru_majflt;
+        c_long ru_nswap;
+        c_long ru_inblock;
+        c_long ru_oublock;
+        c_long ru_msgsnd;
+        c_long ru_msgrcv;
+        c_long ru_nsignals;
+        c_long ru_nvcsw;
+        c_long ru_nivcsw;
+        c_long[16] __reserved;
+    }
+
+    enum
+    {
+        RUSAGE_SELF     =  0,
+        RUSAGE_CHILDREN =  -1,
+    }
+}
 else version (CRuntime_WASI)
 {
     struct rusage
diff --git a/runtime/druntime/src/core/sys/posix/sys/socket.d b/runtime/druntime/src/core/sys/posix/sys/socket.d
index a0e1b97d40e..3cee828529b 100644
--- a/runtime/druntime/src/core/sys/posix/sys/socket.d
+++ b/runtime/druntime/src/core/sys/posix/sys/socket.d
@@ -1603,19 +1603,37 @@ else version (CRuntime_WASI)
     alias socklen_t = uint;
     alias sa_family_t = ushort;
 
-    struct sockaddr
+    version (Emscripten)
     {
-        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-        sa_family_t sa_family;
+        struct sockaddr
+        {
+            sa_family_t sa_family;
+            char[14]    sa_data = 0;
+        }
 
-        byte[0]    sa_data;
+        struct sockaddr_storage
+        {
+            sa_family_t ss_family;
+            char[128 - c_ulong.sizeof - sa_family_t.sizeof] __ss_padding = 0;
+            c_ulong __ss_align;
+        }
     }
-
-    struct sockaddr_storage
+    else
     {
-        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-        sa_family_t ss_family;
-        byte[32] __ss_data;
+        struct sockaddr
+        {
+            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+            sa_family_t sa_family;
+
+            byte[0]    sa_data;
+        }
+
+        struct sockaddr_storage
+        {
+            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+            sa_family_t ss_family;
+            byte[32] __ss_data;
+        }
     }
 
     struct msghdr
diff --git a/runtime/druntime/src/core/sys/posix/sys/un.d b/runtime/druntime/src/core/sys/posix/sys/un.d
index 62a124b974e..efcb02cf73e 100644
--- a/runtime/druntime/src/core/sys/posix/sys/un.d
+++ b/runtime/druntime/src/core/sys/posix/sys/un.d
@@ -104,6 +104,14 @@ else version (Solaris)
         byte[108]    sun_path;
     }
 }
+else version (Emscripten)
+{
+    struct sockaddr_un
+    {
+        sa_family_t  sun_family;
+        byte[108]    sun_path;
+    }
+}
 else version (CRuntime_WASI)
 {
     struct sockaddr_un

From 918f918274fc13dbcfc58924b9875d9bd25f1842 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Wed, 12 Aug 2026 20:15:39 +0200
Subject: [PATCH 09/25] [fix core.sys.posix.sys.types and core.stdc.limits]

Based on the C+ headers.
---
 runtime/druntime/src/core/stdc/limits.d       | 13 +++
 .../druntime/src/core/sys/posix/sys/types.d   | 83 +++++++++++++++++++
 2 files changed, 96 insertions(+)

diff --git a/runtime/druntime/src/core/stdc/limits.d b/runtime/druntime/src/core/stdc/limits.d
index 20f1c0c0f6b..641515399c9 100644
--- a/runtime/druntime/src/core/stdc/limits.d
+++ b/runtime/druntime/src/core/stdc/limits.d
@@ -181,6 +181,19 @@ else version (Windows)
     ///
     enum PIPE_BUF       = 5120;
 }
+else version (Emscripten)
+{
+    ///
+    enum MAX_CANON      = 255;
+    ///
+    enum MAX_INPUT      = 255;
+    ///
+    enum NAME_MAX       = 14;
+    ///
+    enum PATH_MAX       = 256;
+    ///
+    enum PIPE_BUF       = 512;
+}
 else version (CRuntime_WASI)
 {
     ///
diff --git a/runtime/druntime/src/core/sys/posix/sys/types.d b/runtime/druntime/src/core/sys/posix/sys/types.d
index 10defc4f61a..bd313f11c0b 100644
--- a/runtime/druntime/src/core/sys/posix/sys/types.d
+++ b/runtime/druntime/src/core/sys/posix/sys/types.d
@@ -328,6 +328,27 @@ else version (Solaris)
     alias time_t = c_long;
     alias uid_t = uint;
 }
+else version (Emscripten)
+{
+    alias blkcnt_t = int;
+    alias ino_t = ulong;
+    alias off_t = long;
+
+    alias blksize_t = int;
+
+    alias dev_t = uint;
+    alias gid_t = uint;
+    alias mode_t = uint;
+
+    alias nlink_t = size_t;
+
+    alias pid_t = int;
+    //size_t (defined in core.stdc.stddef)
+    alias ssize_t = c_long;
+    alias uid_t = uint;
+
+    alias time_t = long;
+}
 else version (CRuntime_WASI)
 {
     alias blkcnt_t = long;
@@ -460,6 +481,17 @@ else version (Solaris)
     alias zoneid_t = id_t;
     alias ctid_t = id_t;
 }
+else version (Emscripten)
+{
+    alias fsblkcnt_t = ulong;
+    alias fsfilcnt_t = ulong;
+
+    alias clock_t = int;
+    alias id_t = uint;
+    alias key_t = int;
+    alias suseconds_t = int;
+    alias useconds_t = uint;
+}
 else version (CRuntime_WASI)
 {
     alias fsblkcnt_t = ulong;
@@ -776,6 +808,57 @@ version (CRuntime_Glibc)
 
     alias pthread_t = c_ulong;
 }
+else version (Emscripten)
+{
+    struct pthread_attr_t
+    {
+        union
+        {
+            int[10] __i;
+            uint[10] __s;
+        }
+        const(char)* _a_transferredcanvases;
+    }
+
+    union pthread_cond_t
+    {
+        int[12] __i;
+        void*[12] __p;
+    }
+
+    union pthread_mutex_t
+    {
+        int[6] __i;
+        void*[6] __p;
+    }
+
+    union pthread_rwlock_t
+    {
+        int[8] __i;
+        void*[8] __p;
+    }
+
+    struct pthread_rwlockattr_t
+    {
+        uint[2] __attr;
+    }
+
+    alias pthread_key_t = uint;
+
+    struct pthread_condattr_t
+    {
+        uint __attr;
+    }
+
+    struct pthread_mutexattr_t
+    {
+        uint __attr;
+    }
+
+    alias pthread_once_t = int;
+
+    alias pthread_t = c_ulong;
+}
 else version (CRuntime_Musl)
 {
     version (D_LP64)

From 8771d6e8b88945ec9773fcec52bc2a2812960f3a Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Wed, 12 Aug 2026 21:22:21 +0200
Subject: [PATCH 10/25] [fix core.sys.posix.sys.stat]

---
 .../druntime/src/core/sys/posix/sys/stat.d    | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/runtime/druntime/src/core/sys/posix/sys/stat.d b/runtime/druntime/src/core/sys/posix/sys/stat.d
index 5586ca90a37..9836d3d113f 100644
--- a/runtime/druntime/src/core/sys/posix/sys/stat.d
+++ b/runtime/druntime/src/core/sys/posix/sys/stat.d
@@ -1540,6 +1540,36 @@ else version (Solaris)
     enum S_ISGID = 0x400;
     enum S_ISVTX = 0x200;
 }
+else version (Emscripten)
+{
+    struct stat_t
+    {
+        dev_t     st_dev;               /* inode's device */
+        mode_t    st_mode;              /* inode protection mode */
+        nlink_t   st_nlink;             /* number of hard links */
+        uid_t     st_uid;               /* user ID of the file's owner */
+        gid_t     st_gid;               /* group ID of the file's group */
+        dev_t     st_rdev;              /* device type */
+        off_t     st_size;              /* file size, in bytes */
+        blksize_t st_blksize;           /* optimal blocksize for I/O */
+        blkcnt_t  st_blocks;            /* blocks allocated for file */
+        timespec  st_atim;              /* time of last access */
+        timespec  st_mtim;              /* time of last data modification */
+        timespec  st_ctim;              /* time of last file status change */
+        ino_t     st_ino;               /* inode's number */
+
+        extern(D) @safe @property inout pure nothrow
+        {
+            ref inout(time_t) st_atime() return { return st_atim.tv_sec; }
+            ref inout(time_t) st_mtime() return { return st_mtim.tv_sec; }
+            ref inout(time_t) st_ctime() return { return st_ctim.tv_sec; }
+        }
+    }
+
+    enum S_ISUID    = 0x800; // octal 04000
+    enum S_ISGID    = 0x400; // octal 02000
+    enum S_ISVTX    = 0x200; // octal 01000
+}
 else version (CRuntime_WASI)
 {
     struct stat_t
@@ -2302,6 +2332,11 @@ else version (Solaris)
     enum UTIME_NOW = -1;
     enum UTIME_OMIT = -2;
 }
+else version (Emscripten)
+{
+    enum UTIME_NOW = 0x3fffffff;
+    enum UTIME_OMIT = 0x3ffffffe;
+}
 else version (CRuntime_WASI)
 {
     enum UTIME_NOW = -1;
@@ -2413,6 +2448,17 @@ else version (Solaris)
     enum S_IFDOOR = 0xD000;
     enum S_IFPORT = 0xE000;
 }
+else version (Emscripten)
+{
+    enum S_IFMT     = 0xF000; // octal 0170000
+    enum S_IFBLK    = 0x6000; // octal 0060000
+    enum S_IFCHR    = 0x2000; // octal 0020000
+    enum S_IFIFO    = 0x1000; // octal 0010000
+    enum S_IFREG    = 0x8000; // octal 0100000
+    enum S_IFDIR    = 0x4000; // octal 0040000
+    enum S_IFLNK    = 0xA000; // octal 0120000
+    enum S_IFSOCK   = 0xC000; // octal 0140000
+}
 else version (CRuntime_WASI)
 {
     enum S_IFMT     = S_IFBLK | S_IFCHR | S_IFDIR | S_IFIFO | S_IFLNK |

From e4616bfbe1c0d362f597308a62afc85fa2d7bc83 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Wed, 12 Aug 2026 21:23:57 +0200
Subject: [PATCH 11/25] [fix core.sys.posix.sys.socket]

---
 .../druntime/src/core/sys/posix/sys/socket.d  | 123 ++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/runtime/druntime/src/core/sys/posix/sys/socket.d b/runtime/druntime/src/core/sys/posix/sys/socket.d
index 3cee828529b..a673f363baf 100644
--- a/runtime/druntime/src/core/sys/posix/sys/socket.d
+++ b/runtime/druntime/src/core/sys/posix/sys/socket.d
@@ -1598,6 +1598,114 @@ else version (Solaris)
         SHUT_RDWR
     }
 }
+else version (Emscripten)
+{
+    alias socklen_t = uint;
+    alias sa_family_t = ushort;
+
+    struct sockaddr
+    {
+        sa_family_t sa_family;
+        char[14]    sa_data = 0;
+    }
+
+    struct sockaddr_storage
+    {
+        sa_family_t ss_family;
+        char[128 - c_ulong.sizeof - sa_family_t.sizeof] __ss_padding = 0;
+        c_ulong __ss_align;
+    }
+
+    struct msghdr
+    {
+        void*     msg_name;
+        socklen_t msg_namelen;
+        iovec*    msg_iov;
+        int       msg_iovlen;
+        void*     msg_control;
+        socklen_t msg_controllen;
+        int       msg_flags;
+    }
+
+    struct linger
+    {
+        int l_onoff;
+        int l_linger;
+    }
+
+    enum
+    {
+        SOCK_DGRAM      = 2,
+        SOCK_STREAM     = 1,
+    }
+
+    enum
+    {
+        SOL_SOCKET      = 1
+    }
+
+    enum
+    {
+        SO_REUSEADDR = 2,
+        SO_ERROR = 4,
+        SO_SNDBUF = 7,
+        SO_RCVBUF = 8,
+        SO_KEEPALIVE = 9,
+        SO_ACCEPTCONN = 30,
+        SO_PROTOCOL = 38,
+        SO_DOMAIN = 39,
+
+        SO_TYPE = 3
+    }
+
+    version (D_LP64)
+    {
+        enum
+        {
+            SO_RCVTIMEO = 20,
+            SO_SNDTIMEO = 21,
+        }
+    }
+    else
+    {
+        enum
+        {
+            SO_RCVTIMEO = 66,
+            SO_SNDTIMEO = 67,
+        }
+    }
+
+    enum
+    {
+        SOMAXCONN   = 128
+    }
+
+    enum : uint
+    {
+        MSG_DONTWAIT  = 0x0040,
+        MSG_NOSIGNAL  = 0x4000,
+        MSG_PEEK      = 0x0002,
+        MSG_WAITALL   = 0x0100,
+        MSG_TRUNC     = 0x0020
+    }
+
+    enum
+    {
+        PF_UNSPEC = 0,
+        PF_INET = 2,
+
+        AF_UNSPEC  = PF_UNSPEC,
+        AF_INET    = PF_INET,
+        AF_UNIX    = 1,
+    }
+
+    enum
+    {
+        SHUT_RD,
+        SHUT_WR,
+        SHUT_RDWR
+    }
+}
 else version (CRuntime_WASI)
 {
     alias socklen_t = uint;
@@ -2060,6 +2168,14 @@ else version (Solaris)
         AF_INET6 = 26,
     }
 }
+else version (Emscripten)
+{
+    enum
+    {
+        PF_INET6 = 10,
+        AF_INET6 = PF_INET6,
+    }
+}
 else version (CRuntime_WASI)
 {
     enum
@@ -2129,6 +2245,13 @@ else version (Solaris)
         SOCK_RAW = 4,
     }
 }
+else version (Emscripten)
+{
+    enum
+    {
+        SOCK_RAW    = 3
+    }
+}
 else version (CRuntime_WASI)
 {
 }

From f342c2ca0823ff826858dd078e94d6bdbb1abf14 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Thu, 13 Aug 2026 15:12:08 +0200
Subject: [PATCH 12/25] Emscripten: Switch from predefined CRuntime_WASI to
 CRuntime_Musl

---
 .github/actions/5a-emscripten/action.yml      |  8 +-
 .github/workflows/main.yml                    |  2 +-
 driver/main.cpp                               |  2 +-
 runtime/druntime/src/core/demangle.d          |  1 +
 runtime/druntime/src/core/stdc/config.d       |  4 +-
 runtime/druntime/src/core/stdc/errno.d        |  2 +-
 runtime/druntime/src/core/stdc/fenv.d         | 29 ++++---
 runtime/druntime/src/core/stdc/wchar_.d       | 12 +++
 runtime/druntime/src/core/sys/posix/aio.d     |  2 +-
 runtime/druntime/src/core/sys/posix/fcntl.d   | 68 +++++++++++++++++
 .../druntime/src/core/sys/posix/netinet/in_.d | 11 +--
 runtime/druntime/src/core/sys/posix/poll.d    | 16 ++++
 runtime/druntime/src/core/sys/posix/sched.d   |  2 +-
 runtime/druntime/src/core/sys/posix/signal.d  | 76 +++++++++++++++++++
 runtime/druntime/src/core/sys/posix/spawn.d   |  2 +-
 .../druntime/src/core/sys/posix/stdc/time.d   | 19 +----
 .../druntime/src/core/sys/posix/sys/ioctl.d   |  5 ++
 runtime/druntime/src/core/sys/posix/sys/ipc.d |  2 +-
 .../druntime/src/core/sys/posix/sys/mman.d    | 33 ++++++++
 .../src/core/sys/posix/sys/resource.d         |  2 +
 .../druntime/src/core/sys/posix/sys/select.d  |  4 +-
 runtime/druntime/src/core/sys/posix/sys/shm.d |  2 +-
 .../druntime/src/core/sys/posix/sys/socket.d  | 36 +++------
 .../druntime/src/core/sys/posix/sys/wait.d    |  2 +-
 runtime/druntime/src/core/sys/posix/time.d    | 45 ++---------
 runtime/druntime/src/core/thread/osthread.d   |  2 +-
 runtime/druntime/src/rt/sections.d            |  4 +-
 runtime/druntime/src/rt/sections_elf_shared.d |  3 +-
 .../importc_compare/src/importc_compare.d     |  4 +
 runtime/phobos                                |  2 +-
 tests/codegen/emscripten.d                    |  2 +-
 31 files changed, 281 insertions(+), 123 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 08c7c3133da..418f76bdc16 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -1,4 +1,4 @@
-name: "Emscripten: Cross-compile druntime & phobos incl. test runners, install libs + .conf, run druntime unittests"
+name: "Emscripten: Cross-compile druntime & phobos incl. test runners, install libs + .conf, run druntime & phobos unittests"
 inputs:
   arch:
     required: true
@@ -42,6 +42,7 @@ runs:
         cd ../ldc-build-runtime.tmp
 
         ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true
+        ../emsdk/node/*/bin/node ./phobos2-test-runner.js || true
 
     - name: Run `importc_compare`
       shell: bash
@@ -57,10 +58,7 @@ runs:
           -defaultlib=druntime-ldc -L-Linstall/lib-$os-$arch \
           -gcc="$PWD/emsdk/upstream/emscripten/emcc" \
           --mtriple=$triple \
-          --d-version=WASI_EMULATED_SIGNAL \
-          --d-version=WASI_EMULATED_PROCESS_CLOCKS \
-          --d-version=WASI_EMULATED_MMAN \
           -I$PWD/ldc/runtime/druntime/test/importc_compare/src \
           $PWD/ldc/runtime/druntime/test/importc_compare/src/importc_compare.d
 
-        emsdk/node/*/bin/node ./importc_compare.js || true
+        emsdk/node/*/bin/node ./importc_compare.js
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index e214b33616a..6781de0f1b7 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -427,7 +427,7 @@ jobs:
         with:
           os: wasip2
           arch: ${{ matrix.arch }}
-      - name: 'Emscripten: Cross-compile druntime & phobos incl. test runners & run druntime unittests'
+      - name: 'Emscripten: Cross-compile druntime & phobos incl. test runners & run druntime & phobos unittests'
         if: matrix.os == 'emscripten'
         uses: ./.github/actions/5a-emscripten
         with:
diff --git a/driver/main.cpp b/driver/main.cpp
index 55954d834ab..e536ddc5947 100644
--- a/driver/main.cpp
+++ b/driver/main.cpp
@@ -963,7 +963,7 @@ void registerPredefinedTargetVersions() {
     VersionCondition::addPredefinedGlobalIdent("WASI");
     VersionCondition::addPredefinedGlobalIdent("WASIp1");
     VersionCondition::addPredefinedGlobalIdent("Posix");
-    VersionCondition::addPredefinedGlobalIdent("CRuntime_WASI");
+    VersionCondition::addPredefinedGlobalIdent("CRuntime_Musl");
     VersionCondition::addPredefinedGlobalIdent("CppRuntime_LLVM");
     VersionCondition::addPredefinedGlobalIdent("CppRuntime_Clang"); // legacy
     break;
diff --git a/runtime/druntime/src/core/demangle.d b/runtime/druntime/src/core/demangle.d
index bcd7620cd77..6953d6394c2 100644
--- a/runtime/druntime/src/core/demangle.d
+++ b/runtime/druntime/src/core/demangle.d
@@ -3003,6 +3003,7 @@ CXX_DEMANGLER getCXXDemangler() nothrow @trusted
         version (OpenBSD) import core.sys.openbsd.dlfcn : RTLD_DEFAULT;
         version (Darwin) import core.sys.darwin.dlfcn : RTLD_DEFAULT;
         version (Solaris) import core.sys.solaris.dlfcn : RTLD_DEFAULT;
+        version (Emscripten) import core.sys.posix.dlfcn : RTLD_DEFAULT;
         version (CRuntime_WASI) import core.sys.posix.dlfcn : RTLD_DEFAULT;
 
         if (auto found = cast(CXX_DEMANGLER) dlsym(RTLD_DEFAULT, "__cxa_demangle"))
diff --git a/runtime/druntime/src/core/stdc/config.d b/runtime/druntime/src/core/stdc/config.d
index 61b6b66eed1..b4d61f66b97 100644
--- a/runtime/druntime/src/core/stdc/config.d
+++ b/runtime/druntime/src/core/stdc/config.d
@@ -638,7 +638,9 @@ version (unittest)
 // https://musl.libc.org/time64.html
 version (CRuntime_Musl)
 {
-    version (CRuntime_Musl_Pre_Time64)
+    version (Emscripten)
+        enum muslRedirTime64 = false;
+    else version (CRuntime_Musl_Pre_Time64)
         enum muslRedirTime64 = false;
     else
     {
diff --git a/runtime/druntime/src/core/stdc/errno.d b/runtime/druntime/src/core/stdc/errno.d
index 8a956a71687..73fbc5dc577 100644
--- a/runtime/druntime/src/core/stdc/errno.d
+++ b/runtime/druntime/src/core/stdc/errno.d
@@ -2328,7 +2328,7 @@ else version (Haiku)
     enum B_NO_TRANSLATOR                 = (B_TRANSLATION_ERROR_BASE + 1);
     enum B_ILLEGAL_DATA                  = (B_TRANSLATION_ERROR_BASE + 2);
 }
-else version (CRuntime_WASI)
+else version (WASI)
 {
     enum E2BIG           = 1;
     enum EACCES          = 2;
diff --git a/runtime/druntime/src/core/stdc/fenv.d b/runtime/druntime/src/core/stdc/fenv.d
index 9708fc62c86..68c13bc053c 100644
--- a/runtime/druntime/src/core/stdc/fenv.d
+++ b/runtime/druntime/src/core/stdc/fenv.d
@@ -445,19 +445,19 @@ else version (CRuntime_Musl)
         alias fenv_t = uint;
         alias fexcept_t = uint;
     }
-    else
+    else version (Emscripten)
     {
-        static assert(false, "Architecture not supported.");
+        struct fenv_t
+        {
+            uint __cw;
+        }
+
+        alias fexcept_t = ushort;
     }
-}
-else version (Emscripten)
-{
-    struct fenv_t
+    else
     {
-        uint __cw;
+        static assert(false, "Architecture not supported.");
     }
-
-    alias fexcept_t = ushort;
 }
 else version (CRuntime_WASI)
 {
@@ -647,6 +647,17 @@ else version (Solaris)
         static assert(0, "Unimplemented architecture");
     }
 }
+else version (Emscripten)
+{
+    enum
+    {
+        FE_ALL_EXCEPT   = 0, ///
+        FE_TONEAREST    = 0, ///
+        FE_DOWNWARD     = 0x400, ///
+        FE_UPWARD       = 0x800, ///
+        FE_TOWARDZERO   = 0xC00, ///
+    }
+}
 else version (CRuntime_WASI)
 {
     enum
diff --git a/runtime/druntime/src/core/stdc/wchar_.d b/runtime/druntime/src/core/stdc/wchar_.d
index 81af1304152..6c9fc47a073 100644
--- a/runtime/druntime/src/core/stdc/wchar_.d
+++ b/runtime/druntime/src/core/stdc/wchar_.d
@@ -146,6 +146,18 @@ else version (Windows)
     ///
     alias mbstate_t = __mbstate_t;
 }
+else version (Emscripten)
+{
+    ///
+    struct __mbstate_t
+    {
+        uint __opaque1;
+        uint __opaque2;
+    }
+
+    ///
+    alias mbstate_t = __mbstate_t;
+}
 else version (CRuntime_WASI)
 {
     ///
diff --git a/runtime/druntime/src/core/sys/posix/aio.d b/runtime/druntime/src/core/sys/posix/aio.d
index 5a9be3c26f2..37ce24bd624 100644
--- a/runtime/druntime/src/core/sys/posix/aio.d
+++ b/runtime/druntime/src/core/sys/posix/aio.d
@@ -8,7 +8,7 @@
  */
 module core.sys.posix.aio;
 
-version (CRuntime_WASI) {}
+version (WASI) {}
 else:
 
 import core.stdc.config;
diff --git a/runtime/druntime/src/core/sys/posix/fcntl.d b/runtime/druntime/src/core/sys/posix/fcntl.d
index e110c86b3e3..b773cb115df 100644
--- a/runtime/druntime/src/core/sys/posix/fcntl.d
+++ b/runtime/druntime/src/core/sys/posix/fcntl.d
@@ -870,6 +870,74 @@ else version (Solaris)
     enum AT_REMOVEDIR        = 0x1;
     enum AT_EACCESS          = 0x4;
 }
+else version (Emscripten)
+{
+    enum F_GETFD         = 1;
+    enum F_SETFD         = 2;
+    enum F_GETFL         = 3;
+    enum F_SETFL         = 4;
+    enum F_DUPFD         = 0;
+    enum F_DUPFD_CLOEXEC = 1030;
+    version (D_LP64)
+    {
+        enum F_GETLK         = 5;
+        enum F_SETLK         = 6;
+        enum F_SETLKW        = 7;
+    }
+    else
+    {
+        enum F_GETLK         = 12;
+        enum F_SETLK         = 13;
+        enum F_SETLKW        = 14;
+    }
+
+    enum F_RDLCK         = 0;
+    enum F_WRLCK         = 1;
+    enum F_UNLCK         = 2;
+
+    enum FD_CLOEXEC      = 1;
+
+    enum O_APPEND    = 0x400;    // octal 02000
+    enum O_DSYNC     = 0x1000;   // octal 010000
+    enum O_NONBLOCK  = 0x800;    // octal 04000
+    enum O_RSYNC     = 0x101000; // octal 04010000
+    enum O_SYNC      = 0x101000; // octal 04010000
+    enum O_CREAT     = 0x40;     // octal 0100
+    enum O_DIRECTORY = 0x10000;  // octal 0200000
+    enum O_EXCL      = 0x80;     // octal 0200
+    enum O_TRUNC     = 0x200;    // octal 01000
+
+    enum O_NOFOLLOW = 0x20000;  // octal 0400000
+    enum O_EXEC     = 0x200000; // octal 010000000
+    enum O_RDONLY   = 0;
+    enum O_SEARCH   = 0x200000; // octal 010000000
+    enum O_WRONLY   = 1;
+
+    enum O_CLOEXEC = 0x80000; // octal 02000000
+
+    enum O_TTY_INIT = 0;
+
+    enum O_NOCTTY = 0x100; // octal 0400
+
+    enum O_RDWR = 2;
+    enum O_ACCMODE = 3 | O_SEARCH;
+
+    struct flock
+    {
+        short   l_type;
+        short   l_whence;
+        off_t   l_start;
+        off_t   l_len;
+        pid_t   l_pid;
+    }
+
+    enum AT_EACCESS          = 0x200;
+    enum AT_SYMLINK_NOFOLLOW = 0x100;
+    enum AT_SYMLINK_FOLLOW   = 0x400;
+    enum AT_REMOVEDIR        = 0x200;
+
+    enum AT_FDCWD            = -100;
+}
 else version (CRuntime_WASI)
 {
     enum F_GETFD         = 1;
diff --git a/runtime/druntime/src/core/sys/posix/netinet/in_.d b/runtime/druntime/src/core/sys/posix/netinet/in_.d
index 374d762c4b3..276bddd8181 100644
--- a/runtime/druntime/src/core/sys/posix/netinet/in_.d
+++ b/runtime/druntime/src/core/sys/posix/netinet/in_.d
@@ -1631,15 +1631,8 @@ else version (CRuntime_WASI)
         ubyte[16] s6_addr;
     }
     struct sockaddr_in6 {
-        version (Emscripten) // no alignment override
-        {
-            sa_family_t     sin6_family;
-        }
-        else
-        {
-            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-            sa_family_t     sin6_family;
-        }
+        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+        sa_family_t     sin6_family;
 
         in_port_t       sin6_port;
         uint            sin6_flowinfo;
diff --git a/runtime/druntime/src/core/sys/posix/poll.d b/runtime/druntime/src/core/sys/posix/poll.d
index bf7594ab548..5f3d315430f 100644
--- a/runtime/druntime/src/core/sys/posix/poll.d
+++ b/runtime/druntime/src/core/sys/posix/poll.d
@@ -351,6 +351,22 @@ else version (Solaris)
         POLLNVAL    = 0x0020,
     }
 }
+else version (Emscripten)
+{
+    enum
+    {
+        POLLIN      = 0x0001,
+        POLLPRI     = 0x0002,
+        POLLOUT     = 0x0004,
+        POLLRDNORM  = 0x0040,
+        POLLRDBAND  = 0x0080,
+        POLLWRNORM  = 0x0100,
+        POLLWRBAND  = 0x0200,
+        POLLERR     = 0x0008,
+        POLLHUP     = 0x0010,
+        POLLNVAL    = 0x0020,
+    }
+}
 else version (CRuntime_WASI)
 {
     enum
diff --git a/runtime/druntime/src/core/sys/posix/sched.d b/runtime/druntime/src/core/sys/posix/sched.d
index b5f5a3b496c..cc89f54fd8f 100644
--- a/runtime/druntime/src/core/sys/posix/sched.d
+++ b/runtime/druntime/src/core/sys/posix/sched.d
@@ -169,7 +169,7 @@ else version (Solaris)
     enum SCHED_FX = 6;
     enum _SCHED_NEXT = 7;
 }
-else version (CRuntime_WASI)
+else version (WASI)
 {
     struct sched_param
     {
diff --git a/runtime/druntime/src/core/sys/posix/signal.d b/runtime/druntime/src/core/sys/posix/signal.d
index 9ebf39f982f..9eed4fa8415 100644
--- a/runtime/druntime/src/core/sys/posix/signal.d
+++ b/runtime/druntime/src/core/sys/posix/signal.d
@@ -596,6 +596,35 @@ else version (Solaris)
     enum SIGUSR2 = 17;
     enum SIGURG = 21;
 }
+else version (Emscripten)
+{
+    enum SIGHUP     = 1;
+    //SIGINT (defined in core.stdc.signal)
+    enum SIGQUIT    = 3;
+    //SIGILL (defined in core.stdc.signal)
+    //SIGABRT (defined in core.stdc.signal)
+    enum SIGIOT     = SIGABRT;
+    enum SIGBUS     = 7;
+    //SIGFPE (defined in core.stdc.signal)
+    enum SIGKILL    = 9;
+    enum SIGUSR1    = 10;
+    //SIGSEGV (defined in core.stdc.signal)
+    enum SIGUSR2    = 12;
+    enum SIGPIPE    = 13;
+    enum SIGALRM    = 14;
+    //SIGTERM (defined in core.stdc.signal)
+    enum SIGSTKFLT  = 16;
+    enum SIGCHLD    = 17;
+    enum SIGCONT    = 18;
+    enum SIGSTOP    = 19;
+    enum SIGTSTP    = 20;
+    enum SIGTTIN    = 21;
+    enum SIGTTOU    = 22;
+    enum SIGURG     = 23;
+    enum SIGWINCH   = 28;
+    enum SIGIO      = 29;
+    enum SIGPWR     = 30;
+}
 else version (CRuntime_WASI)
 {
     enum SIGHUP     = 1;
@@ -912,6 +941,20 @@ else version (Darwin)
         int             sa_flags;
     }
 }
+else version (Emscripten)
+{
+    struct sigaction_t
+    {
+        union
+        {
+            sigfn_t     sa_handler;
+            sigactfn_t  sa_sigaction;
+        }
+        sigset_t        sa_mask;
+        int             sa_flags;
+        void function() sa_restorer;
+    }
+}
 else version (CRuntime_WASI)
 {
 }
@@ -1496,6 +1539,8 @@ else version (Emscripten)
     enum SIG_UNBLOCK    = 1;
     enum SIG_SETMASK    = 2;
 
+    struct siginfo_t; // FIXME
+
     enum
     {
         SI_ASYNCNL = -60,
@@ -2501,6 +2546,17 @@ else version (Solaris)
         POLL_HUP,
     }
 }
+else version (Emscripten)
+{
+    enum SIGPOLL    = 29;
+    enum SIGPROF    = 27;
+    enum SIGSYS     = 31;
+    enum SIGTRAP    = 5;
+    enum SIGVTALRM  = 26;
+    enum SIGXCPU    = 24;
+    enum SIGXFSZ    = 25;
+    enum SIGUNUSED  = SIGSYS;
+}
 else version (CRuntime_WASI)
 {
     enum SIGPOLL    = 29;
@@ -3140,6 +3196,26 @@ else version (Solaris)
         int __sigev_pad2;
     }
 }
+else version (Emscripten)
+{
+    struct sigevent
+    {
+        sigval sigev_value;
+        int sigev_signo;
+        int sigev_notify;
+
+        union
+        {
+            byte[64 - 2 * int.sizeof - sigval.sizeof] __pad;
+            pid_t sigev_notify_thread_id;
+            struct
+            {
+                void function(sigval) sigev_notify_function;
+                pthread_attr_t* sigev_notify_attributes;
+            }
+        }
+    }
+}
 else version (CRuntime_WASI)
 {
 }
diff --git a/runtime/druntime/src/core/sys/posix/spawn.d b/runtime/druntime/src/core/sys/posix/spawn.d
index a22957c0f1f..ddd9d765efc 100644
--- a/runtime/druntime/src/core/sys/posix/spawn.d
+++ b/runtime/druntime/src/core/sys/posix/spawn.d
@@ -9,7 +9,7 @@
  */
 module core.sys.posix.spawn;
 
-version (CRuntime_WASI) {}
+version (WASI) {}
 else:
 
 /*
diff --git a/runtime/druntime/src/core/sys/posix/stdc/time.d b/runtime/druntime/src/core/sys/posix/stdc/time.d
index 8adad1b2594..3278751f591 100644
--- a/runtime/druntime/src/core/sys/posix/stdc/time.d
+++ b/runtime/druntime/src/core/sys/posix/stdc/time.d
@@ -34,24 +34,7 @@ nothrow:
 @nogc:
 
 ///
-version (Emscripten)
-{
-    struct tm
-    {
-        int     tm_sec;     /// seconds after the minute [0-60]
-        int     tm_min;     /// minutes after the hour [0-59]
-        int     tm_hour;    /// hours since midnight [0-23]
-        int     tm_mday;    /// day of the month [1-31]
-        int     tm_mon;     /// months since January [0-11]
-        int     tm_year;    /// years since 1900
-        int     tm_wday;    /// days since Sunday [0-6]
-        int     tm_yday;    /// days since January 1 [0-365]
-        int     tm_isdst;   /// Daylight Savings Time flag
-        c_long  tm_gmtoff;  /// offset from CUT in seconds
-        char*   tm_zone;    /// timezone abbreviation
-    }
-}
-else version (CRuntime_WASI)
+version (CRuntime_WASI)
 {
     struct tm
     {
diff --git a/runtime/druntime/src/core/sys/posix/sys/ioctl.d b/runtime/druntime/src/core/sys/posix/sys/ioctl.d
index a6b458390c7..0407df42f5e 100644
--- a/runtime/druntime/src/core/sys/posix/sys/ioctl.d
+++ b/runtime/druntime/src/core/sys/posix/sys/ioctl.d
@@ -400,6 +400,11 @@ else version (DragonFlyBSD)
 else version (Solaris)
 {
 }
+else version (Emscripten)
+{
+    enum FIONREAD = 0x541B;
+    enum FIONBIO  = 0x5421;
+}
 else version (CRuntime_WASI)
 {
     enum FIONREAD = 1;
diff --git a/runtime/druntime/src/core/sys/posix/sys/ipc.d b/runtime/druntime/src/core/sys/posix/sys/ipc.d
index 7d1472cd40d..f11bae61b90 100644
--- a/runtime/druntime/src/core/sys/posix/sys/ipc.d
+++ b/runtime/druntime/src/core/sys/posix/sys/ipc.d
@@ -14,7 +14,7 @@
  */
 module core.sys.posix.sys.ipc;
 
-version (CRuntime_WASI) {}
+version (WASI) {}
 else:
 
 import core.sys.posix.config;
diff --git a/runtime/druntime/src/core/sys/posix/sys/mman.d b/runtime/druntime/src/core/sys/posix/sys/mman.d
index aafef576670..2f07e3dc532 100644
--- a/runtime/druntime/src/core/sys/posix/sys/mman.d
+++ b/runtime/druntime/src/core/sys/posix/sys/mman.d
@@ -185,6 +185,14 @@ else version (DragonFlyBSD)
 else version (Solaris)
 {
 }
+else version (Emscripten)
+{
+    enum POSIX_MADV_NORMAL      = 0;
+    enum POSIX_MADV_RANDOM      = 1;
+    enum POSIX_MADV_SEQUENTIAL  = 2;
+    enum POSIX_MADV_WILLNEED    = 3;
+    enum POSIX_MADV_DONTNEED    = 4;
+}
 else version (CRuntime_WASI)
 {
     enum POSIX_MADV_NORMAL      = 0;
@@ -257,6 +265,13 @@ else version (Solaris)
     enum PROT_WRITE = 0x02;
     enum PROT_EXEC = 0x04;
 }
+else version (Emscripten)
+{
+    enum PROT_NONE = 0x00;
+    enum PROT_READ = 0x01;
+    enum PROT_WRITE = 0x02;
+    enum PROT_EXEC = 0x04;
+}
 else version (CRuntime_WASI)
 {
     enum PROT_NONE = 0x00;
@@ -512,6 +527,19 @@ else version (Solaris)
     enum MS_ASYNC = 0x0001;
     enum MS_INVALIDATE  = 0x0002;
 }
+else version (Emscripten)
+{
+    enum MAP_SHARED     = 0x0001;
+    enum MAP_PRIVATE    = 0x0002;
+    enum MAP_FIXED      = 0x0010;
+    enum MAP_ANON       = 0x0020;
+
+    enum MAP_FAILED     = cast(void*)-1;
+
+    enum MS_ASYNC       = 0x0001;
+    enum MS_INVALIDATE  = 0x0002;
+    enum MS_SYNC        = 0x0004;
+}
 else version (CRuntime_WASI)
 {
     enum MAP_SHARED     = 0x0001;
@@ -645,6 +673,11 @@ else version (Solaris)
     enum MCL_CURRENT = 0x0001;
     enum MCL_FUTURE = 0x0002;
 }
+else version (Emscripten)
+{
+    enum MCL_CURRENT = 0x0001;
+    enum MCL_FUTURE = 0x0002;
+}
 else version (CRuntime_WASI)
 {
     enum MCL_CURRENT = 0x0001;
diff --git a/runtime/druntime/src/core/sys/posix/sys/resource.d b/runtime/druntime/src/core/sys/posix/sys/resource.d
index b147fced256..5b1c8a8428d 100644
--- a/runtime/druntime/src/core/sys/posix/sys/resource.d
+++ b/runtime/druntime/src/core/sys/posix/sys/resource.d
@@ -498,6 +498,8 @@ else version (Solaris)
 }
 else version (Emscripten)
 {
+    alias rlim_t = ulong;
+
     struct rusage
     {
         timeval ru_utime;
diff --git a/runtime/druntime/src/core/sys/posix/sys/select.d b/runtime/druntime/src/core/sys/posix/sys/select.d
index b3c1395829a..0459b99550a 100644
--- a/runtime/druntime/src/core/sys/posix/sys/select.d
+++ b/runtime/druntime/src/core/sys/posix/sys/select.d
@@ -474,7 +474,7 @@ else version (CRuntime_Musl)
 {
     enum FD_SETSIZE = 1024;
 
-    alias fd_mask = ulong;
+    alias fd_mask = c_ulong;
 
     private
     {
@@ -492,7 +492,7 @@ else version (CRuntime_Musl)
     }
 
     struct fd_set {
-        ulong[FD_SETSIZE / 8 / long.sizeof] fds_bits;
+        c_ulong[FD_SETSIZE / 8 / c_long.sizeof] fds_bits;
     }
 
     extern (D) void FD_CLR()( int fd, fd_set* fdset ) pure
diff --git a/runtime/druntime/src/core/sys/posix/sys/shm.d b/runtime/druntime/src/core/sys/posix/sys/shm.d
index 4a3aca91a23..cdf762589c0 100644
--- a/runtime/druntime/src/core/sys/posix/sys/shm.d
+++ b/runtime/druntime/src/core/sys/posix/sys/shm.d
@@ -14,7 +14,7 @@
  */
 module core.sys.posix.sys.shm;
 
-version (CRuntime_WASI) {}
+version (WASI) {}
 else:
 
 import core.sys.posix.config;
diff --git a/runtime/druntime/src/core/sys/posix/sys/socket.d b/runtime/druntime/src/core/sys/posix/sys/socket.d
index a673f363baf..0302907c5fc 100644
--- a/runtime/druntime/src/core/sys/posix/sys/socket.d
+++ b/runtime/druntime/src/core/sys/posix/sys/socket.d
@@ -1711,37 +1711,19 @@ else version (CRuntime_WASI)
     alias socklen_t = uint;
     alias sa_family_t = ushort;
 
-    version (Emscripten)
+    struct sockaddr
     {
-        struct sockaddr
-        {
-            sa_family_t sa_family;
-            char[14]    sa_data = 0;
-        }
+        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+        sa_family_t sa_family;
 
-        struct sockaddr_storage
-        {
-            sa_family_t ss_family;
-            char[128 - c_ulong.sizeof - sa_family_t.sizeof] __ss_padding = 0;
-            c_ulong __ss_align;
-        }
+        byte[0]    sa_data;
     }
-    else
-    {
-        struct sockaddr
-        {
-            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-            sa_family_t sa_family;
-
-            byte[0]    sa_data;
-        }
 
-        struct sockaddr_storage
-        {
-            align(16) // __BIGGEST_ALIGNMENT__ on Wasm
-            sa_family_t ss_family;
-            byte[32] __ss_data;
-        }
+    struct sockaddr_storage
+    {
+        align(16) // __BIGGEST_ALIGNMENT__ on Wasm
+        sa_family_t ss_family;
+        byte[32] __ss_data;
     }
 
     struct msghdr
diff --git a/runtime/druntime/src/core/sys/posix/sys/wait.d b/runtime/druntime/src/core/sys/posix/sys/wait.d
index 99d300c2ccd..2953f945d70 100644
--- a/runtime/druntime/src/core/sys/posix/sys/wait.d
+++ b/runtime/druntime/src/core/sys/posix/sys/wait.d
@@ -14,7 +14,7 @@
  */
 module core.sys.posix.sys.wait;
 
-version (CRuntime_WASI) {}
+version (WASI) {}
 else:
 
 import core.sys.posix.config;
diff --git a/runtime/druntime/src/core/sys/posix/time.d b/runtime/druntime/src/core/sys/posix/time.d
index aad88d35ece..c110bbc9c2f 100644
--- a/runtime/druntime/src/core/sys/posix/time.d
+++ b/runtime/druntime/src/core/sys/posix/time.d
@@ -278,6 +278,14 @@ else version (Solaris)
 
     alias timestruc_t = timespec;
 }
+else version (Emscripten)
+{
+    struct timespec
+    {
+        time_t  tv_sec;
+        c_long  tv_nsec;
+    }
+}
 else version (CRuntime_WASI)
 {
     struct timespec
@@ -543,43 +551,6 @@ else version (CRuntime_Musl)
     int timer_settime(timer_t, int, const scope itimerspec*, itimerspec*);
     int timer_getoverrun(timer_t);
 }
-else version (Emscripten)
-{
-    alias clockid_t = int;
-    alias timer_t = void*;
-
-    struct itimerspec
-    {
-        timespec it_interval;
-        timespec it_value;
-    }
-
-    enum TIMER_ABSTIME = 1;
-
-    enum CLOCK_REALTIME = 0;
-    enum CLOCK_PROCESS_CPUTIME_ID = 2;
-    enum CLOCK_THREAD_CPUTIME_ID = 3;
-    enum CLOCK_REALTIME_COARSE = 5;
-    enum CLOCK_BOOTTIME = 7;
-    enum CLOCK_REALTIME_ALARM = 8;
-    enum CLOCK_BOOTTIME_ALARM = 9;
-    enum CLOCK_SGI_CYCLE = 10;
-    enum CLOCK_TAI = 11;
-
-    int nanosleep(const scope timespec*, timespec*);
-
-    int clock_getres(clockid_t, timespec*);
-    int clock_gettime(clockid_t, timespec*);
-    int clock_settime(clockid_t, const scope timespec*);
-    int clock_nanosleep(clockid_t, int, const scope timespec*, timespec*);
-    int clock_getcpuclockid(pid_t, clockid_t *);
-
-    //int timer_create(clockid_t, sigevent*, timer_t*);
-    int timer_delete(timer_t);
-    int timer_gettime(timer_t, itimerspec*);
-    int timer_settime(timer_t, int, const scope itimerspec*, itimerspec*);
-    int timer_getoverrun(timer_t);
-}
 else version (CRuntime_WASI)
 {
     alias clockid_t = const __clockid*;
diff --git a/runtime/druntime/src/core/thread/osthread.d b/runtime/druntime/src/core/thread/osthread.d
index 5255ef61a02..03fc8a30b96 100644
--- a/runtime/druntime/src/core/thread/osthread.d
+++ b/runtime/druntime/src/core/thread/osthread.d
@@ -100,7 +100,7 @@ else version (Posix)
     static import core.sys.posix.pthread;
     import core.stdc.errno : EINTR, errno;
 
-    version (CRuntime_WASI)
+    version (WASI)
         import core.sys.posix.pthread : pthread_attr_destroy, pthread_attr_getstack,
             pthread_attr_init, pthread_attr_setstacksize, pthread_create, pthread_detach,
             pthread_join, pthread_self, sched_yield;
diff --git a/runtime/druntime/src/rt/sections.d b/runtime/druntime/src/rt/sections.d
index 2beeb2e06f5..2c569a2526e 100644
--- a/runtime/druntime/src/rt/sections.d
+++ b/runtime/druntime/src/rt/sections.d
@@ -24,6 +24,8 @@ else version (WatchOS)
 
 version (GNU)
     public import gcc.sections;
+else version (WebAssembly)
+    public import rt.sections_wasm;
 else version (CRuntime_Glibc)
     public import rt.sections_elf_shared;
 else version (CRuntime_Musl)
@@ -69,8 +71,6 @@ else version (CRuntime_Bionic)
     public import rt.sections_elf_shared;
 else version (CRuntime_UClibc)
     public import rt.sections_elf_shared;
-else version (WebAssembly)
-    public import rt.sections_wasm;
 else
     static assert(0, "unimplemented");
 
diff --git a/runtime/druntime/src/rt/sections_elf_shared.d b/runtime/druntime/src/rt/sections_elf_shared.d
index 585c451a1be..a75ff3c78d3 100644
--- a/runtime/druntime/src/rt/sections_elf_shared.d
+++ b/runtime/druntime/src/rt/sections_elf_shared.d
@@ -19,7 +19,8 @@ else version (TVOS)
 else version (WatchOS)
     version = Darwin;
 
-version (CRuntime_Glibc) enum SharedELF = true;
+version (Emscripten) enum SharedELF = false;
+else version (CRuntime_Glibc) enum SharedELF = true;
 else version (CRuntime_Musl) enum SharedELF = true;
 else version (FreeBSD) enum SharedELF = true;
 else version (NetBSD) enum SharedELF = true;
diff --git a/runtime/druntime/test/importc_compare/src/importc_compare.d b/runtime/druntime/test/importc_compare/src/importc_compare.d
index 62f0feec8e4..608fe754324 100644
--- a/runtime/druntime/test/importc_compare/src/importc_compare.d
+++ b/runtime/druntime/test/importc_compare/src/importc_compare.d
@@ -73,6 +73,10 @@ immutable ErrorFilter[] knownProblems = [
     ErrorFilter("core.sys.posix.sys.types.pthread_mutex_t", "", "CRuntime_WASI", 0, ""),
     ErrorFilter("core.sys.posix.sys.types.pthread_rwlock_t", "", "CRuntime_WASI", 0, ""),
     ErrorFilter("core.sys.posix.sys.types.pthread_barrier_t", "", "CRuntime_WASI", 0, ""),
+    ErrorFilter("core.sys.posix.sys.types.pthread_cond_t", "", "Emscripten", 0, ""),
+    ErrorFilter("core.sys.posix.sys.types.pthread_mutex_t", "", "Emscripten", 0, ""),
+    ErrorFilter("core.sys.posix.sys.types.pthread_rwlock_t", "", "Emscripten", 0, ""),
+    ErrorFilter("core.sys.posix.sys.types.pthread_barrier_t", "", "Emscripten", 0, ""),
 ];
 
 struct ErrorFilter
diff --git a/runtime/phobos b/runtime/phobos
index 7b79b4a1c9e..27419a0108c 160000
--- a/runtime/phobos
+++ b/runtime/phobos
@@ -1 +1 @@
-Subproject commit 7b79b4a1c9e6ad2164f016c7789d39bc915f6fba
+Subproject commit 27419a0108c511faa13643d11af35176fce810bd
diff --git a/tests/codegen/emscripten.d b/tests/codegen/emscripten.d
index cf72136bc3f..d705d55cc46 100644
--- a/tests/codegen/emscripten.d
+++ b/tests/codegen/emscripten.d
@@ -10,7 +10,7 @@ version (Emscripten) {} else static assert(0);
 version (WASI) {} else static assert(0);
 version (WASIp1) {} else static assert(0);
 version (Posix) {} else static assert(0);
-version (CRuntime_WASI) {} else static assert(0);
+version (CRuntime_Musl) {} else static assert(0);
 version (CppRuntime_LLVM) {} else static assert(0);
 
 

From 06c29f286d117c62fad04e7ff07b6f5e8012b5ba Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Thu, 13 Aug 2026 20:26:12 +0200
Subject: [PATCH 13/25] [CI: Try mounting host timezone DB into node process]

---
 .github/actions/5a-emscripten/action.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 418f76bdc16..d754e646d13 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -18,6 +18,7 @@ runs:
         bootstrap-ldc/bin/ldc-build-runtime \
           --ninja \
           --dFlags="-mtriple=$triple" \
+          --linkerFlags="--preload-file;/usr/share/zoneinfo@/tz" \
           --ldcSrcDir="$PWD/ldc" \
           --installWithSuffix="-$os-$arch" \
           --testrunners \
@@ -41,6 +42,7 @@ runs:
         set -eux
         cd ../ldc-build-runtime.tmp
 
+        export TZDIR=/tz
         ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true
         ../emsdk/node/*/bin/node ./phobos2-test-runner.js || true
 

From 346bf95bbeb6ab6777d73e7bf1ec05981c6c324b Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Thu, 13 Aug 2026 22:33:19 +0200
Subject: [PATCH 14/25] [finish removal of wasm-ld linker special case]

---
 .github/actions/4b-test-lit/action.yml |  3 +--
 tests/baremetal/wasm.d                 |  2 +-
 tests/baremetal/wasm2.d                |  2 +-
 tests/codegen/wasm.d                   |  2 +-
 tests/lit.site.cfg.in                  | 10 ----------
 5 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/.github/actions/4b-test-lit/action.yml b/.github/actions/4b-test-lit/action.yml
index 77ac54d1559..c8aeed7344c 100644
--- a/.github/actions/4b-test-lit/action.yml
+++ b/.github/actions/4b-test-lit/action.yml
@@ -23,8 +23,7 @@ runs:
         fi
 
         cd ../build
-        # temporarily add LLVM bin dir to PATH, so that e.g. wasm-ld is found
-        PATH="$PWD/../llvm/bin:$PATH" ctest -V -R "lit-tests"
+        ctest -V -R "lit-tests"
 
     - name: 'Windows: Run LIT testsuite'
       if: runner.os == 'Windows'
diff --git a/tests/baremetal/wasm.d b/tests/baremetal/wasm.d
index 7146965eb8a..6a066e9da6e 100644
--- a/tests/baremetal/wasm.d
+++ b/tests/baremetal/wasm.d
@@ -1,7 +1,7 @@
 // Compile and link directly to naked WebAssembly.
 
 // REQUIRES: target_WebAssembly
-// REQUIRES: link_WebAssembly
+// REQUIRES: internal_lld
 // RUN: %ldc -mtriple=wasm32-unknown-unknown -w %s
 
 extern(C): // no mangling
diff --git a/tests/baremetal/wasm2.d b/tests/baremetal/wasm2.d
index 1d2e37ae217..ee4caf4aaae 100644
--- a/tests/baremetal/wasm2.d
+++ b/tests/baremetal/wasm2.d
@@ -1,7 +1,7 @@
 // A more complex naked wasm example using Phobos templates.
 
 // REQUIRES: target_WebAssembly
-// REQUIRES: link_WebAssembly
+// REQUIRES: internal_lld
 
 // RUN: %ldc -mtriple=wasm32-unknown-unknown -w -L--export-dynamic %s -of=%t.wasm
 
diff --git a/tests/codegen/wasm.d b/tests/codegen/wasm.d
index 9c2323348c3..25f48b93395 100644
--- a/tests/codegen/wasm.d
+++ b/tests/codegen/wasm.d
@@ -1,4 +1,4 @@
-// REQUIRES: target_WebAssembly, link_WebAssembly
+// REQUIRES: target_WebAssembly, internal_lld
 
 // emit textual IR *and* compile & link
 
diff --git a/tests/lit.site.cfg.in b/tests/lit.site.cfg.in
index ed6d98153ba..6d1a67aecd2 100644
--- a/tests/lit.site.cfg.in
+++ b/tests/lit.site.cfg.in
@@ -132,16 +132,6 @@ if canDoLTO:
 if config.ldc_with_lld:
     config.available_features.add('internal_lld')
 
-# Add "link_WebAssembly" feature if we can link wasm (-link-internally or wasm-ld in PATH).
-if config.ldc_with_lld:
-    config.available_features.add('link_WebAssembly')
-else:
-    try:
-        if (subprocess.call(["wasm-ld", "--version"]) == 0):
-            config.available_features.add('link_WebAssembly')
-    except OSError:
-        pass
-
 config.target_triple = '(unused)'
 
 # test_exec_root: The root path where tests should be run.

From 2d81f40eed25c50185200bba6641cdbb46e20e2f Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Thu, 13 Aug 2026 23:57:52 +0200
Subject: [PATCH 15/25] [add -Xcc=-nostdlib to 55-target-wasm-naked.conf]

---
 CMakeLists.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 53da9cf9ba1..75c06c27f3a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -952,7 +952,7 @@ makeConfSection(NAME "51-target-wasm-base"
         ${wasm_eh_switches}
 )
 
-# Add a convenience config for *naked* wasm targets, omitting druntime/Phobos
+# Add a convenience config for *naked* wasm targets, omitting druntime/Phobos/libc
 # (and preferring built-in lld for linking) automatically.
 set(wasm_naked_link_internally)
 if(LDC_WITH_LLD)
@@ -962,6 +962,7 @@ makeConfSection(NAME "55-target-wasm-naked"
     SECTION "^wasm(32|64)-.*-(unknown|none)"
     SWITCHES
         -defaultlib=
+        -Xcc=-nostdlib
         ${wasm_naked_link_internally}
     LIB_DIRS OVERRIDE
 )

From 7ef92df3f3273bff2cc9f9d52bce22da4ffdb52e Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Fri, 14 Aug 2026 00:12:20 +0200
Subject: [PATCH 16/25] [avoid warning wrt. ignored -Xcc switches when using
 -link-internally]

---
 CMakeLists.txt | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 75c06c27f3a..b96a47657a6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -954,16 +954,18 @@ makeConfSection(NAME "51-target-wasm-base"
 
 # Add a convenience config for *naked* wasm targets, omitting druntime/Phobos/libc
 # (and preferring built-in lld for linking) automatically.
-set(wasm_naked_link_internally)
+set(wasm_naked_switches)
 if(LDC_WITH_LLD)
-    set(wasm_naked_link_internally -link-internally)
+    list(APPEND wasm_naked_switches -link-internally)
+else()
+    # clang as default cross-linker driver usually works, with -nostdlib
+    list(APPEND wasm_naked_switches -Xcc=-nostdlib)
 endif()
 makeConfSection(NAME "55-target-wasm-naked"
     SECTION "^wasm(32|64)-.*-(unknown|none)"
     SWITCHES
         -defaultlib=
-        -Xcc=-nostdlib
-        ${wasm_naked_link_internally}
+        ${wasm_naked_switches}
     LIB_DIRS OVERRIDE
 )
 

From ca0e64facf68a7bd30c60fee4b0bd44673b7081f Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Fri, 14 Aug 2026 13:58:14 +0200
Subject: [PATCH 17/25] [fix core.sync.event unittest failure]

---
 .github/actions/5a-emscripten/action.yml | 4 ++--
 runtime/druntime/src/core/sync/event.d   | 7 ++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index d754e646d13..4c69302b208 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -33,8 +33,8 @@ runs:
         set -eux
         cd ../ldc-build-runtime.tmp
 
-        ../emsdk/node/*/bin/node ./druntime-test-runner-debug.js || true
-        ../emsdk/node/*/bin/node ./druntime-test-runner.js || true
+        ../emsdk/node/*/bin/node ./druntime-test-runner-debug.js
+        ../emsdk/node/*/bin/node ./druntime-test-runner.js
 
     - name: Run phobos unittests
       shell: bash
diff --git a/runtime/druntime/src/core/sync/event.d b/runtime/druntime/src/core/sync/event.d
index 9c8cb1b0250..237ba055857 100644
--- a/runtime/druntime/src/core/sync/event.d
+++ b/runtime/druntime/src/core/sync/event.d
@@ -269,7 +269,12 @@ nothrow @nogc:
             int result = 0;
             if (!m_state)
             {
-                if (tmout == Duration.max)
+                version (Emscripten)
+                {
+                    // pthread_cond_[timed]wait() seems to be a stub always returning 0
+                    result = -1;
+                }
+                else if (tmout == Duration.max)
                 {
                     result = pthread_cond_wait(&m_cond, &m_mutex);
                 }

From 4459e8d47874358188db33644621ccdb3c7af4de Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Fri, 14 Aug 2026 14:50:03 +0200
Subject: [PATCH 18/25] [try using default Posix timezone data dir]

---
 .github/actions/5a-emscripten/action.yml | 3 +--
 runtime/phobos                           | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 4c69302b208..1d728273b73 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -18,7 +18,7 @@ runs:
         bootstrap-ldc/bin/ldc-build-runtime \
           --ninja \
           --dFlags="-mtriple=$triple" \
-          --linkerFlags="--preload-file;/usr/share/zoneinfo@/tz" \
+          --linkerFlags="--preload-file;/usr/share/zoneinfo" \
           --ldcSrcDir="$PWD/ldc" \
           --installWithSuffix="-$os-$arch" \
           --testrunners \
@@ -42,7 +42,6 @@ runs:
         set -eux
         cd ../ldc-build-runtime.tmp
 
-        export TZDIR=/tz
         ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true
         ../emsdk/node/*/bin/node ./phobos2-test-runner.js || true
 
diff --git a/runtime/phobos b/runtime/phobos
index 27419a0108c..a26e3c03bbe 160000
--- a/runtime/phobos
+++ b/runtime/phobos
@@ -1 +1 @@
-Subproject commit 27419a0108c511faa13643d11af35176fce810bd
+Subproject commit a26e3c03bbec90c601894e8b8f77d8af37141ba0

From 2830c3949fd87ac7c1c2342440cd4b1c295bbbf7 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Fri, 14 Aug 2026 20:15:52 +0200
Subject: [PATCH 19/25] [Phobos: Hack around lacking TZ env var support]

---
 .github/actions/5a-emscripten/action.yml | 4 ++--
 runtime/phobos                           | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/actions/5a-emscripten/action.yml b/.github/actions/5a-emscripten/action.yml
index 1d728273b73..44068eedf53 100644
--- a/.github/actions/5a-emscripten/action.yml
+++ b/.github/actions/5a-emscripten/action.yml
@@ -42,8 +42,8 @@ runs:
         set -eux
         cd ../ldc-build-runtime.tmp
 
-        ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js || true
-        ../emsdk/node/*/bin/node ./phobos2-test-runner.js || true
+        ../emsdk/node/*/bin/node ./phobos2-test-runner-debug.js
+        ../emsdk/node/*/bin/node ./phobos2-test-runner.js
 
     - name: Run `importc_compare`
       shell: bash
diff --git a/runtime/phobos b/runtime/phobos
index a26e3c03bbe..bdada788953 160000
--- a/runtime/phobos
+++ b/runtime/phobos
@@ -1 +1 @@
-Subproject commit a26e3c03bbec90c601894e8b8f77d8af37141ba0
+Subproject commit bdada788953c2f6f199ce8eb52303c007cf337fa

From 7cbdd31559d284acc6515195c0c9ce36b9edb960 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sat, 15 Aug 2026 15:14:50 +0200
Subject: [PATCH 20/25] [polish]

---
 .github/workflows/main.yml                    |   2 +-
 runtime/druntime/src/core/stdc/errno.d        | 146 +++++++++++++-
 runtime/druntime/src/core/stdc/fenv.d         |   2 +-
 runtime/druntime/src/core/stdc/wctype.d       |   5 +-
 runtime/druntime/src/core/sys/posix/poll.d    |   6 +-
 runtime/druntime/src/core/sys/posix/sched.d   |  24 ++-
 runtime/druntime/src/core/sys/posix/signal.d  | 183 ++++++++++++++----
 .../druntime/src/core/sys/posix/sys/socket.d  |  14 +-
 .../druntime/src/core/sys/posix/sys/types.d   | 105 ++++------
 runtime/druntime/src/core/sys/posix/time.d    |   2 +
 runtime/druntime/src/rt/sections_elf_shared.d |   2 +-
 11 files changed, 379 insertions(+), 112 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 6781de0f1b7..1400f982947 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -440,7 +440,7 @@ jobs:
           arch: ${{ matrix.arch }}
           os: ${{ matrix.os }}
           is_addon: true
-      - name: 'Smoke-test add-on package'
+      - name: Smoke-test add-on package
         run: |
           set -eux
           # unpack addon archive into ../bootstrap-ldc
diff --git a/runtime/druntime/src/core/stdc/errno.d b/runtime/druntime/src/core/stdc/errno.d
index 73fbc5dc577..f2575a26eef 100644
--- a/runtime/druntime/src/core/stdc/errno.d
+++ b/runtime/druntime/src/core/stdc/errno.d
@@ -2328,7 +2328,7 @@ else version (Haiku)
     enum B_NO_TRANSLATOR                 = (B_TRANSLATION_ERROR_BASE + 1);
     enum B_ILLEGAL_DATA                  = (B_TRANSLATION_ERROR_BASE + 2);
 }
-else version (WASI)
+else version (CRuntime_WASI)
 {
     enum E2BIG           = 1;
     enum EACCES          = 2;
@@ -2410,6 +2410,150 @@ else version (WASI)
     enum EOPNOTSUPP      = ENOTSUP;
     enum EWOULDBLOCK     = EAGAIN;
 }
+else version (Emscripten)
+{
+    // mostly WASI compatible:
+    enum E2BIG           = 1;
+    enum EACCES          = 2;
+    enum EADDRINUSE      = 3;
+    enum EADDRNOTAVAIL   = 4;
+    enum EAFNOSUPPORT    = 5;
+    enum EAGAIN          = 6;
+    enum EALREADY        = 7;
+    enum EBADF           = 8;
+    enum EBADMSG         = 9;
+    enum EBUSY           = 10;
+    enum ECANCELED       = 11;
+    enum ECHILD          = 12;
+    enum ECONNABORTED    = 13;
+    enum ECONNREFUSED    = 14;
+    enum ECONNRESET      = 15;
+    enum EDEADLK         = 16;
+    enum EDESTADDRREQ    = 17;
+    enum EDOM            = 18;
+    enum EDQUOT          = 19;
+    enum EEXIST          = 20;
+    enum EFAULT          = 21;
+    enum EFBIG           = 22;
+    enum EHOSTUNREACH    = 23;
+    enum EIDRM           = 24;
+    enum EILSEQ          = 25;
+    enum EINPROGRESS     = 26;
+    enum EINTR           = 27;
+    enum EINVAL          = 28;
+    enum EIO             = 29;
+    enum EISCONN         = 30;
+    enum EISDIR          = 31;
+    enum ELOOP           = 32;
+    enum EMFILE          = 33;
+    enum EMLINK          = 34;
+    enum EMSGSIZE        = 35;
+    enum EMULTIHOP       = 36;
+    enum ENAMETOOLONG    = 37;
+    enum ENETDOWN        = 38;
+    enum ENETRESET       = 39;
+    enum ENETUNREACH     = 40;
+    enum ENFILE          = 41;
+    enum ENOBUFS         = 42;
+    enum ENODEV          = 43;
+    enum ENOENT          = 44;
+    enum ENOEXEC         = 45;
+    enum ENOLCK          = 46;
+    enum ENOLINK         = 47;
+    enum ENOMEM          = 48;
+    enum ENOMSG          = 49;
+    enum ENOPROTOOPT     = 50;
+    enum ENOSPC          = 51;
+    enum ENOSYS          = 52;
+    enum ENOTCONN        = 53;
+    enum ENOTDIR         = 54;
+    enum ENOTEMPTY       = 55;
+    enum ENOTRECOVERABLE = 56;
+    enum ENOTSOCK        = 57;
+    // different (see below): ENOTSUP
+    enum ENOTTY          = 59;
+    enum ENXIO           = 60;
+    enum EOVERFLOW       = 61;
+    enum EOWNERDEAD      = 62;
+    enum EPERM           = 63;
+    enum EPIPE           = 64;
+    enum EPROTO          = 65;
+    enum EPROTONOSUPPORT = 66;
+    enum EPROTOTYPE      = 67;
+    enum ERANGE          = 68;
+    enum EROFS           = 69;
+    enum ESPIPE          = 70;
+    enum ESRCH           = 71;
+    enum ESTALE          = 72;
+    enum ETIMEDOUT       = 73;
+    enum ETXTBSY         = 74;
+    enum EXDEV           = 75;
+    // not defined: ENOTCAPABLE
+
+    // extra codes:
+    enum ENOSTR          = 100;
+    enum EBFONT          = 101;
+    enum EBADSLT         = 102;
+    enum EBADRQC         = 103;
+    enum ENOANO          = 104;
+    enum ENOTBLK         = 105;
+    enum ECHRNG          = 106;
+    enum EL3HLT          = 107;
+    enum EL3RST          = 108;
+    enum ELNRNG          = 109;
+    enum EUNATCH         = 110;
+    enum ENOCSI          = 111;
+    enum EL2HLT          = 112;
+    enum EBADE           = 113;
+    enum EBADR           = 114;
+    enum EXFULL          = 115;
+    enum ENODATA         = 116;
+    enum ETIME           = 117;
+    enum ENOSR           = 118;
+    enum ENONET          = 119;
+    enum ENOPKG          = 120;
+    enum EREMOTE         = 121;
+    enum EADV            = 122;
+    enum ESRMNT          = 123;
+    enum ECOMM           = 124;
+    enum EDOTDOT         = 125;
+    enum ENOTUNIQ        = 126;
+    enum EBADFD          = 127;
+    enum EREMCHG         = 128;
+    enum ELIBACC         = 129;
+    enum ELIBBAD         = 130;
+    enum ELIBSCN         = 131;
+    enum ELIBMAX         = 132;
+    enum ELIBEXEC        = 133;
+    enum ERESTART        = 134;
+    enum ESTRPIPE        = 135;
+    enum EUSERS          = 136;
+    enum ESOCKTNOSUPPORT = 137;
+    enum EOPNOTSUPP      = 138;
+    enum EPFNOSUPPORT    = 139;
+    enum ESHUTDOWN       = 140;
+    enum ETOOMANYREFS    = 141;
+    enum EHOSTDOWN       = 142;
+    enum EUCLEAN         = 143;
+    enum ENOTNAM         = 144;
+    enum ENAVAIL         = 145;
+    enum EISNAM          = 146;
+    enum EREMOTEIO       = 147;
+    enum ENOMEDIUM       = 148;
+    enum EMEDIUMTYPE     = 149;
+    enum ENOKEY          = 150;
+    enum EKEYEXPIRED     = 151;
+    enum EKEYREVOKED     = 152;
+    enum EKEYREJECTED    = 153;
+    enum ERFKILL         = 154;
+    enum EHWPOISON       = 155;
+    enum EL2NSYNC        = 156;
+
+    // musl aliases:
+    enum EWOULDBLOCK     = EAGAIN;
+    enum EDEADLOCK       = EDEADLK;
+    enum ENOTSUP         = EOPNOTSUPP;
+}
 else
 {
     static assert(false, "Unsupported platform");
diff --git a/runtime/druntime/src/core/stdc/fenv.d b/runtime/druntime/src/core/stdc/fenv.d
index 68c13bc053c..e95f878cc18 100644
--- a/runtime/druntime/src/core/stdc/fenv.d
+++ b/runtime/druntime/src/core/stdc/fenv.d
@@ -440,7 +440,7 @@ else version (CRuntime_Musl)
         }
         alias fexcept_t = uint;
     }
-    else version (RICV64)
+    else version (RISCV64)
     {
         alias fenv_t = uint;
         alias fexcept_t = uint;
diff --git a/runtime/druntime/src/core/stdc/wctype.d b/runtime/druntime/src/core/stdc/wctype.d
index 2b55f3decbb..88d97cc8ebb 100644
--- a/runtime/druntime/src/core/stdc/wctype.d
+++ b/runtime/druntime/src/core/stdc/wctype.d
@@ -32,7 +32,10 @@ version (CRuntime_Glibc)
 else version (CRuntime_Musl)
 {
     ///
-    alias wctype_t = c_ulong;
+    version (Emscripten)
+        alias wctype_t = uint; // for wasm64 too
+    else
+        alias wctype_t = c_ulong;
     ///
     alias wctrans_t = const(int)*;
 }
diff --git a/runtime/druntime/src/core/sys/posix/poll.d b/runtime/druntime/src/core/sys/posix/poll.d
index 5f3d315430f..344c24b3509 100644
--- a/runtime/druntime/src/core/sys/posix/poll.d
+++ b/runtime/druntime/src/core/sys/posix/poll.d
@@ -358,13 +358,13 @@ else version (Emscripten)
         POLLIN      = 0x0001,
         POLLPRI     = 0x0002,
         POLLOUT     = 0x0004,
+        POLLERR     = 0x0008,
+        POLLHUP     = 0x0010,
+        POLLNVAL    = 0x0020,
         POLLRDNORM  = 0x0040,
         POLLRDBAND  = 0x0080,
         POLLWRNORM  = 0x0100,
         POLLWRBAND  = 0x0200,
-        POLLERR     = 0x0008,
-        POLLHUP     = 0x0010,
-        POLLNVAL    = 0x0020,
     }
 }
 else version (CRuntime_WASI)
diff --git a/runtime/druntime/src/core/sys/posix/sched.d b/runtime/druntime/src/core/sys/posix/sched.d
index cc89f54fd8f..3dd41400cc4 100644
--- a/runtime/druntime/src/core/sys/posix/sched.d
+++ b/runtime/druntime/src/core/sys/posix/sched.d
@@ -169,7 +169,29 @@ else version (Solaris)
     enum SCHED_FX = 6;
     enum _SCHED_NEXT = 7;
 }
-else version (WASI)
+else version (Emscripten)
+{
+    struct sched_param
+    {
+        int sched_priority;
+        int __reserved1;
+        struct __timespec32
+        {
+            time_t __reserved1;
+            c_long __reserved2;
+        }
+        __timespec32[2] __reserved2;
+        int __reserved3;
+    }
+
+    enum SCHED_OTHER = 0;
+    enum SCHED_FIFO = 1;
+    enum SCHED_RR = 2;
+    enum SCHED_BATCH = 3;
+    enum SCHED_IDLE = 5;
+    enum SCHED_RESET_ON_FORK = 0x40000000;
+}
+else version (CRuntime_WASI)
 {
     struct sched_param
     {
diff --git a/runtime/druntime/src/core/sys/posix/signal.d b/runtime/druntime/src/core/sys/posix/signal.d
index 9eed4fa8415..f404f42d412 100644
--- a/runtime/druntime/src/core/sys/posix/signal.d
+++ b/runtime/druntime/src/core/sys/posix/signal.d
@@ -425,30 +425,6 @@ version (linux)
         enum SIGUSR2    = 12;
         enum SIGURG     = 23;
     }
-    else version (Emscripten)
-    {
-        //SIGABRT (defined in core.stdc.signal)
-        enum SIGALRM    = 14;
-        enum SIGBUS     = 7;
-        enum SIGCHLD    = 17;
-        enum SIGCONT    = 18;
-        //SIGFPE (defined in core.stdc.signal)
-        enum SIGHUP     = 1;
-        //SIGILL (defined in core.stdc.signal)
-        //SIGINT (defined in core.stdc.signal)
-        enum SIGKILL    = 9;
-        enum SIGPIPE    = 13;
-        enum SIGQUIT    = 3;
-        //SIGSEGV (defined in core.stdc.signal)
-        enum SIGSTOP    = 19;
-        //SIGTERM (defined in core.stdc.signal)
-        enum SIGTSTP    = 20;
-        enum SIGTTIN    = 21;
-        enum SIGTTOU    = 22;
-        enum SIGUSR1    = 10;
-        enum SIGUSR2    = 12;
-        enum SIGURG     = 23;
-    }
     else
         static assert(0, "unimplemented");
 }
@@ -1529,17 +1505,85 @@ else version (Solaris)
 }
 else version (Emscripten)
 {
+    enum SIG_HOLD = cast(sigfn_t2) 2;
+
     struct sigset_t
     {
         c_ulong[2] __bits;
-
     }
 
+    enum SA_NOCLDSTOP   = 1;
+
     enum SIG_BLOCK      = 0;
     enum SIG_UNBLOCK    = 1;
     enum SIG_SETMASK    = 2;
 
-    struct siginfo_t; // FIXME
+    struct siginfo_t
+    {
+        int si_signo;
+        int si_errno;
+        int si_code;
+
+        union /* __si_fields */
+        {
+            byte[128 - 2 * int.sizeof - c_long.sizeof] __pad;
+
+            struct /* __si_common */
+            {
+                union /* __first */
+                {
+                    struct /* __piduid */
+                    {
+                        pid_t si_pid;
+                        uid_t si_uid;
+                    }
+                    struct /* __timer */
+                    {
+                        int si_timerid;
+                        int si_overrun;
+                    }
+                }
+                union /* __second */
+                {
+                    sigval si_value;
+                    struct /* __sigchld */
+                    {
+                        int si_status;
+                        clock_t si_utime;
+                        clock_t si_stime;
+                    }
+                }
+            }
+
+            struct /* __sigfault */
+            {
+                void* si_addr;
+                short si_addr_lsb;
+                union /* __first */
+                {
+                    struct /* __addr_bnd */
+                    {
+                        void* si_lower;
+                        void* si_upper;
+                    }
+                    uint si_pkey;
+                }
+            }
+
+            struct /* __sigpoll */
+            {
+                c_long si_band;
+                int si_fd;
+            }
+
+            struct /* __sigsys */
+            {
+                void* si_call_addr;
+                int si_syscall;
+                uint si_arch;
+            }
+        }
+    }
 
     enum
     {
@@ -1945,16 +1989,6 @@ version (linux)
         enum SIGXCPU    = 24;
         enum SIGXFSZ    = 25;
     }
-    else version (Emscripten)
-    {
-        enum SIGPOLL    = 29;
-        enum SIGPROF    = 27;
-        enum SIGSYS     = 31;
-        enum SIGTRAP    = 5;
-        enum SIGVTALRM  = 26;
-        enum SIGXCPU    = 24;
-        enum SIGXFSZ    = 25;
-    }
     else
         static assert(0, "unimplemented");
 
@@ -2556,6 +2590,79 @@ else version (Emscripten)
     enum SIGXCPU    = 24;
     enum SIGXFSZ    = 25;
     enum SIGUNUSED  = SIGSYS;
+
+    enum SA_ONSTACK   = 0x08000000;
+    enum SA_RESETHAND = 0x80000000;
+    enum SA_RESTART   = 0x10000000;
+    enum SA_SIGINFO   = 4;
+    enum SA_NOCLDWAIT = 2;
+    enum SA_NODEFER   = 0x40000000;
+
+    enum SA_NOMASK      = SA_NODEFER;
+    enum SA_ONESHOT     = SA_RESETHAND;
+
+    enum
+    {
+        ILL_ILLOPC = 1,
+        ILL_ILLOPN,
+        ILL_ILLADR,
+        ILL_ILLTRP,
+        ILL_PRVOPC,
+        ILL_PRVREG,
+        ILL_COPROC,
+        ILL_BADSTK
+    }
+
+    enum
+    {
+        FPE_INTDIV = 1,
+        FPE_INTOVF,
+        FPE_FLTDIV,
+        FPE_FLTOVF,
+        FPE_FLTUND,
+        FPE_FLTRES,
+        FPE_FLTINV,
+        FPE_FLTSUB
+    }
+
+    enum
+    {
+        SEGV_MAPERR = 1,
+        SEGV_ACCERR
+    }
+
+    enum
+    {
+        BUS_ADRALN = 1,
+        BUS_ADRERR,
+        BUS_OBJERR
+    }
+
+    enum
+    {
+        TRAP_BRKPT = 1,
+        TRAP_TRACE
+    }
+
+    enum
+    {
+        CLD_EXITED = 1,
+        CLD_KILLED,
+        CLD_DUMPED,
+        CLD_TRAPPED,
+        CLD_STOPPED,
+        CLD_CONTINUED
+    }
+
+    enum
+    {
+        POLL_IN = 1,
+        POLL_OUT,
+        POLL_MSG,
+        POLL_ERR,
+        POLL_PRI,
+        POLL_HUP
+    }
 }
 else version (CRuntime_WASI)
 {
@@ -3204,11 +3311,11 @@ else version (Emscripten)
         int sigev_signo;
         int sigev_notify;
 
-        union
+        union /* __sev_fields */
         {
             byte[64 - 2 * int.sizeof - sigval.sizeof] __pad;
             pid_t sigev_notify_thread_id;
-            struct
+            struct /* __sev_thread */
             {
                 void function(sigval) sigev_notify_function;
                 pthread_attr_t* sigev_notify_attributes;
diff --git a/runtime/druntime/src/core/sys/posix/sys/socket.d b/runtime/druntime/src/core/sys/posix/sys/socket.d
index 0302907c5fc..5bbcbf81f3a 100644
--- a/runtime/druntime/src/core/sys/posix/sys/socket.d
+++ b/runtime/druntime/src/core/sys/posix/sys/socket.d
@@ -1600,19 +1600,21 @@ else version (Solaris)
 }
 else version (Emscripten)
 {
+    // note: this is only a subset of the C declarations (covering what CRuntime_WASI does below)
+
     alias socklen_t = uint;
     alias sa_family_t = ushort;
 
     struct sockaddr
     {
         sa_family_t sa_family;
-        char[14]    sa_data = 0;
+        byte[14]    sa_data;
     }
 
     struct sockaddr_storage
     {
         sa_family_t ss_family;
-        char[128 - c_ulong.sizeof - sa_family_t.sizeof] __ss_padding = 0;
+        byte[128 - c_ulong.sizeof - sa_family_t.sizeof] __ss_padding;
         c_ulong __ss_align;
     }
 
@@ -1621,9 +1623,17 @@ else version (Emscripten)
         void*     msg_name;
         socklen_t msg_namelen;
         iovec*    msg_iov;
+        version (D_LP64) version (BigEndian)
+            int __pad1;
         int       msg_iovlen;
+        version (D_LP64) version (LittleEndian)
+            int __pad1;
         void*     msg_control;
+        version (D_LP64) version (BigEndian)
+            int __pad2;
         socklen_t msg_controllen;
+        version (D_LP64) version (LittleEndian)
+            int __pad2;
         int       msg_flags;
     }
 
diff --git a/runtime/druntime/src/core/sys/posix/sys/types.d b/runtime/druntime/src/core/sys/posix/sys/types.d
index bd313f11c0b..00cb777fb08 100644
--- a/runtime/druntime/src/core/sys/posix/sys/types.d
+++ b/runtime/druntime/src/core/sys/posix/sys/types.d
@@ -330,13 +330,13 @@ else version (Solaris)
 }
 else version (Emscripten)
 {
-    alias blkcnt_t = int;
+    alias blkcnt_t = int; // for wasm64 too
     alias ino_t = ulong;
     alias off_t = long;
 
-    alias blksize_t = int;
+    alias blksize_t = int; // for wasm64 too
 
-    alias dev_t = uint;
+    alias dev_t = uint; // for wasm64 too
     alias gid_t = uint;
     alias mode_t = uint;
 
@@ -344,7 +344,7 @@ else version (Emscripten)
 
     alias pid_t = int;
     //size_t (defined in core.stdc.stddef)
-    alias ssize_t = c_long;
+    alias ssize_t = ptrdiff_t;
     alias uid_t = uint;
 
     alias time_t = long;
@@ -486,10 +486,10 @@ else version (Emscripten)
     alias fsblkcnt_t = ulong;
     alias fsfilcnt_t = ulong;
 
-    alias clock_t = int;
+    alias clock_t = int; // for wasm64 too
     alias id_t = uint;
     alias key_t = int;
-    alias suseconds_t = int;
+    alias suseconds_t = int; // for wasm64 too
     alias useconds_t = uint;
 }
 else version (CRuntime_WASI)
@@ -808,65 +808,29 @@ version (CRuntime_Glibc)
 
     alias pthread_t = c_ulong;
 }
-else version (Emscripten)
-{
-    struct pthread_attr_t
-    {
-        union
-        {
-            int[10] __i;
-            uint[10] __s;
-        }
-        const(char)* _a_transferredcanvases;
-    }
-
-    union pthread_cond_t
-    {
-        int[12] __i;
-        void*[12] __p;
-    }
-
-    union pthread_mutex_t
-    {
-        int[6] __i;
-        void*[6] __p;
-    }
-
-    union pthread_rwlock_t
-    {
-        int[8] __i;
-        void*[8] __p;
-    }
-
-    struct pthread_rwlockattr_t
-    {
-        uint[2] __attr;
-    }
-
-    alias pthread_key_t = uint;
-
-    struct pthread_condattr_t
-    {
-        uint __attr;
-    }
-
-    struct pthread_mutexattr_t
-    {
-        uint __attr;
-    }
-
-    alias pthread_once_t = int;
-
-    alias pthread_t = c_ulong;
-}
 else version (CRuntime_Musl)
 {
     version (D_LP64)
     {
-        union pthread_attr_t
+        version (Emscripten)
         {
-            int[14] __i;
-            ulong[7] __s;
+            struct pthread_attr_t
+            {
+                union
+                {
+                    int[10] __i;
+                    c_ulong[10] __s;
+                }
+                const(char)* _a_transferredcanvases;
+            }
+        }
+        else
+        {
+            union pthread_attr_t
+            {
+                int[14] __i;
+                ulong[7] __s;
+            }
         }
 
         union pthread_cond_t
@@ -889,10 +853,25 @@ else version (CRuntime_Musl)
     }
     else
     {
-        union pthread_attr_t
+        version (Emscripten)
         {
-            int[9] __i;
-            uint[9] __s;
+            struct pthread_attr_t
+            {
+                union
+                {
+                    int[10] __i;
+                    c_ulong[10] __s;
+                }
+                const(char)* _a_transferredcanvases;
+            }
+        }
+        else
+        {
+            union pthread_attr_t
+            {
+                int[9] __i;
+                uint[9] __s;
+            }
         }
 
         union pthread_cond_t
diff --git a/runtime/druntime/src/core/sys/posix/time.d b/runtime/druntime/src/core/sys/posix/time.d
index c110bbc9c2f..6471206adea 100644
--- a/runtime/druntime/src/core/sys/posix/time.d
+++ b/runtime/druntime/src/core/sys/posix/time.d
@@ -283,7 +283,9 @@ else version (Emscripten)
     struct timespec
     {
         time_t  tv_sec;
+        int : 8 * (time_t.sizeof - c_long.sizeof) * (BYTE_ORDER == BIG_ENDIAN);
         c_long  tv_nsec;
+        int : 8 * (time_t.sizeof - c_long.sizeof) * (BYTE_ORDER != BIG_ENDIAN);
     }
 }
 else version (CRuntime_WASI)
diff --git a/runtime/druntime/src/rt/sections_elf_shared.d b/runtime/druntime/src/rt/sections_elf_shared.d
index a75ff3c78d3..a3c5d810005 100644
--- a/runtime/druntime/src/rt/sections_elf_shared.d
+++ b/runtime/druntime/src/rt/sections_elf_shared.d
@@ -19,7 +19,7 @@ else version (TVOS)
 else version (WatchOS)
     version = Darwin;
 
-version (Emscripten) enum SharedELF = false;
+version (WebAssembly) enum SharedELF = false;
 else version (CRuntime_Glibc) enum SharedELF = true;
 else version (CRuntime_Musl) enum SharedELF = true;
 else version (FreeBSD) enum SharedELF = true;

From 9beaff69974ed326cb694f1d67449688f31f0e41 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sat, 15 Aug 2026 17:58:39 +0200
Subject: [PATCH 21/25] [changelog]

---
 CHANGELOG.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e6745052666..1fd727a9f56 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,11 +5,12 @@
   - `-foptimize-nothrow` is the default setting when targeting Windows or WebAssembly, to make hitting https://github.com/ldc-developers/ldc/issues/3504 much less likely.
 - Support for [LLVM 22](https://releases.llvm.org/22.1.0/docs/ReleaseNotes.html). The prebuilt packages use v22.1.8. (#5097, #5102, #5172)
 - Minimum LLVM version raised to 18. (#5094)
-- DRuntime and Phobos now support [WASI](https://github.com/WebAssembly/WASI) preview levels 1 and 2, based on [`wasi-libc`](https://github.com/WebAssembly/wasi-libc). Two caveats being that WASI is strictly single-threaded (currently), and that fibers are unavailable. (#5186, #5229, #5230, #5242)
+- DRuntime and Phobos now support [WASI](https://github.com/WebAssembly/WASI) preview levels 1 and 2, based on [`wasi-libc`](https://github.com/WebAssembly/wasi-libc), as well as [Emscripten](https://emscripten.org/). Two caveats being that WASI (and our Emscripten support) is strictly single-threaded (currently), and that fibers are unavailable. (#5186, #5229, #5230, #5242, #5259)
 - New prebuilt **addon packages** (`ldc2-*-addon-<target OS>.tar.xz`) for simple cross-compilation. Simply unpack them directly into your LDC installation directory, and then cross-compile via `-mtriple=…` (or `dub --target=…`): (#5240)
   - Windows: `x86_64-windows-msvc`, `i686-windows-msvc`; no SDK required.
   - Android: `aarch64-linux-android30`, `armv7a-linux-androideabi29`, `x86_64-linux-android29`, `i686-linux-android29`; needs an [Android NDK](https://developer.android.com/ndk/downloads) (r27) and its `toolchains/llvm/prebuilt/*/bin/` dir in your PATH.
   - WASI: `wasm32-unknown-wasip1`, `wasm32-unknown-wasip2`; needs a [WASI SDK](https://github.com/webassembly/wasi-sdk) and its `bin/` dir in your PATH. (#5207, #5242)
+  - Emscripten: `wasm32-unknown-emscripten`; needs a [Emscripten SDK](https://github.com/emscripten-core/emsdk) and its `upstream/emscripten/` dir in your PATH. (#5259)
 - The `@ldc.attributes.restrict` UDA is now supported for dynamic-array parameters too. Builtin array ops (`c[] = a[] * b[]` etc.) use it, enabling auto-vectorization. Note that for such array ops, the dlang spec prescribes that the slice on the left and any slices on the right must not overlap (https://dlang.org/spec/arrays.html#array-operations), and this knowledge is now used by the optimizer; e.g., `x[] *= x[]` is invalid. (#5148, #5168, #5176)
 - DMD-style inline assembly: `asm { naked; }` is now much less of a special case wrt. codegen - such naked functions are now emitted as if `asm { naked; }` was replaced with the `@naked` function UDA. IR-wise, they are not emitted as module-level asm blobs anymore, but regular IR functions. This should lift a few former `asm { naked; }`-specific restrictions and fixed at least one LTO issue. (#5041)
 - **dcompute**: Added support for Native device code Embedding (PTX and SPIR-V) into the host executable's `.rodata` section. (#5140)

From 33d6afbf65ec69f439410578e3b4a57bcd8831a5 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sat, 15 Aug 2026 22:41:08 +0200
Subject: [PATCH 22/25] [polish phobos]

---
 runtime/phobos | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/runtime/phobos b/runtime/phobos
index bdada788953..4d4842eff1f 160000
--- a/runtime/phobos
+++ b/runtime/phobos
@@ -1 +1 @@
-Subproject commit bdada788953c2f6f199ce8eb52303c007cf337fa
+Subproject commit 4d4842eff1f50b9edd90b9a7fc470a7b2fc4e85c

From aad13389338cd9b5cae1aafce06c6f81f507ba71 Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sun, 16 Aug 2026 11:30:17 +0200
Subject: [PATCH 23/25] [fix core.stdc.limits]

---
 runtime/druntime/src/core/stdc/limits.d | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/runtime/druntime/src/core/stdc/limits.d b/runtime/druntime/src/core/stdc/limits.d
index 641515399c9..466273fc3f0 100644
--- a/runtime/druntime/src/core/stdc/limits.d
+++ b/runtime/druntime/src/core/stdc/limits.d
@@ -188,11 +188,11 @@ else version (Emscripten)
     ///
     enum MAX_INPUT      = 255;
     ///
-    enum NAME_MAX       = 14;
+    enum NAME_MAX       = 255;
     ///
-    enum PATH_MAX       = 256;
+    enum PATH_MAX       = 4096;
     ///
-    enum PIPE_BUF       = 512;
+    enum PIPE_BUF       = 4096;
 }
 else version (CRuntime_WASI)
 {

From 1956ff6243d907226a86e05240a2ff8772af146b Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sun, 16 Aug 2026 15:07:39 +0200
Subject: [PATCH 24/25] [fix remaining mismatching constants reported by
 importc_compare, except for generally broken MB_LEN_MAX]

---
 runtime/druntime/src/core/stdc/math.d   | 12 ++++++++++--
 runtime/druntime/src/core/stdc/signal.d | 12 ++++++++++--
 runtime/druntime/src/core/stdc/stddef.d |  5 +++++
 runtime/druntime/src/core/stdc/wchar_.d | 12 ++++++++++--
 4 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/runtime/druntime/src/core/stdc/math.d b/runtime/druntime/src/core/stdc/math.d
index 9642a5d800d..e65bc80d913 100644
--- a/runtime/druntime/src/core/stdc/math.d
+++ b/runtime/druntime/src/core/stdc/math.d
@@ -214,8 +214,16 @@ else
 enum int MATH_ERRNO       = 1;
 ///
 enum int MATH_ERREXCEPT   = 2;
-///
-enum int math_errhandling = MATH_ERRNO | MATH_ERREXCEPT;
+version (Emscripten)
+{
+    ///
+    enum int math_errhandling = 2;
+}
+else
+{
+    ///
+    enum int math_errhandling = MATH_ERRNO | MATH_ERREXCEPT;
+}
 
 version (none)
 {
diff --git a/runtime/druntime/src/core/stdc/signal.d b/runtime/druntime/src/core/stdc/signal.d
index 6abfea47c6c..81fc2c380b1 100644
--- a/runtime/druntime/src/core/stdc/signal.d
+++ b/runtime/druntime/src/core/stdc/signal.d
@@ -63,8 +63,16 @@ else version (Posix)
     enum SIG_ERR    = cast(sigfn_t) -1;
     ///
     enum SIG_DFL    = cast(sigfn_t) 0;
-    ///
-    enum SIG_IGN    = cast(sigfn_t) 1;
+    version (Emscripten)
+    {
+        ///
+        enum SIG_IGN    = cast(sigfn_t) -2;
+    }
+    else
+    {
+        ///
+        enum SIG_IGN    = cast(sigfn_t) 1;
+    }
 
     // standard C signals
     ///
diff --git a/runtime/druntime/src/core/stdc/stddef.d b/runtime/druntime/src/core/stdc/stddef.d
index a147248e48d..d2ed7b3e747 100644
--- a/runtime/druntime/src/core/stdc/stddef.d
+++ b/runtime/druntime/src/core/stdc/stddef.d
@@ -29,6 +29,11 @@ version (Windows)
     ///
     alias wchar_t = wchar;
 }
+else version (Emscripten)
+{
+    ///
+    alias wchar_t = int;
+}
 else version (Posix)
 {
     ///
diff --git a/runtime/druntime/src/core/stdc/wchar_.d b/runtime/druntime/src/core/stdc/wchar_.d
index 6c9fc47a073..a382a873032 100644
--- a/runtime/druntime/src/core/stdc/wchar_.d
+++ b/runtime/druntime/src/core/stdc/wchar_.d
@@ -179,8 +179,16 @@ else
 ///
 alias wint_t = wchar_t;
 
-///
-enum wchar_t WEOF = 0xFFFF;
+version (Emscripten)
+{
+    ///
+    enum WEOF = uint.max;
+}
+else
+{
+    ///
+    enum wchar_t WEOF = 0xFFFF;
+}
 
 version (CRuntime_Glibc)
 {

From e18b0553fd79558ab559e1ae8423d612157ccf6d Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <noone@nowhere.com>
Date: Sun, 16 Aug 2026 15:28:14 +0200
Subject: [PATCH 25/25] [oh, Phobos depends on wchar_t being a Unicode char
 type, not int]

---
 runtime/druntime/src/core/stdc/stddef.d |  5 ----
 runtime/druntime/src/core/stdc/stdint.d | 33 ++++++++++++++++++-------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/runtime/druntime/src/core/stdc/stddef.d b/runtime/druntime/src/core/stdc/stddef.d
index d2ed7b3e747..a147248e48d 100644
--- a/runtime/druntime/src/core/stdc/stddef.d
+++ b/runtime/druntime/src/core/stdc/stddef.d
@@ -29,11 +29,6 @@ version (Windows)
     ///
     alias wchar_t = wchar;
 }
-else version (Emscripten)
-{
-    ///
-    alias wchar_t = int;
-}
 else version (Posix)
 {
     ///
diff --git a/runtime/druntime/src/core/stdc/stdint.d b/runtime/druntime/src/core/stdc/stdint.d
index 33db7a9cec6..eccaa7cd15d 100644
--- a/runtime/druntime/src/core/stdc/stdint.d
+++ b/runtime/druntime/src/core/stdc/stdint.d
@@ -537,15 +537,30 @@ enum sig_atomic_t SIG_ATOMIC_MAX = sig_atomic_t.max;
 ///
 enum size_t  SIZE_MAX  = size_t.max;
 
-///
-enum wchar_t WCHAR_MIN = wchar_t.min;
-///
-enum wchar_t WCHAR_MAX = wchar_t.max;
-
-///
-enum wint_t  WINT_MIN  = wint_t.min;
-///
-enum wint_t  WINT_MAX  = wint_t.max;
+version (Emscripten) // wchar_t/wint_t is actually int
+{
+    ///
+    enum WCHAR_MIN = int.min;
+    ///
+    enum WCHAR_MAX = int.max;
+
+    ///
+    enum WINT_MIN  = int.min;
+    ///
+    enum WINT_MAX  = int.max;
+}
+else
+{
+    ///
+    enum wchar_t WCHAR_MIN = wchar_t.min;
+    ///
+    enum wchar_t WCHAR_MAX = wchar_t.max;
+
+    ///
+    enum wint_t  WINT_MIN  = wint_t.min;
+    ///
+    enum wint_t  WINT_MAX  = wint_t.max;
+}
 
 ///
 alias INT8_C  = _typify!int8_t ;