arch/sim: replace macOS C++ constructor runtime hack with post-link patch

[xiaoxiang781216]

Summary

Replace the macOS sim C++ global constructor runtime hack (sim_macho_init.c)
with a post-link Mach-O section patching scheme so dyld no longer auto-runs
constructors before NuttX is initialized.

Impact

• Area: arch/sim (macOS host only). Linux behavior is unchanged.

Testing

• Build host: macOS (Ventura VM)
• Target: sim:nsh with CONFIG_HAVE_CXX=y / CONFIG_HAVE_CXXINITIALIZE=y
• Verified via standalone test (test_sinit7) that the C++ constructor is
  deferred past main() and is only invoked when explicitly called through
  the _sinit[]/_einit[] loop in lib_cxx_initialize().

Details

1. Link with -Wl,-ld_classic,-no_fixup_chains to keep the classic
   __mod_init_func pointer format (prevents ld64 from converting it to
   __init_offsets).
2. Post-link, run patch_macho_initsection.py (python3 + lief) to patch
   the Mach-O section type flags from MOD_INIT_FUNC_POINTERS /
   INIT_FUNC_OFFSETS to REGULAR, so dyld skips them.
3. Use the Mach-O auto-generated boundary symbols
   section$start$__DATA_CONST$__mod_init_func /
   section$end$__DATA_CONST$__mod_init_func, mapped via __asm() labels in
   arch/sim/include/arch.h to the common _sinit[]/_einit[] names used
   by lib_cxx_initialize().
4. Delete the old sim_macho_init.c runtime hack and the macOS-specific
   macho_call_saved_init_funcs() path in lib_cxx_initialize.c.

Dependency: pip install lief on the build host when
CONFIG_HAVE_CXXINITIALIZE=y.

[Copilot]

Pull request overview

This PR replaces the macOS simulator C++ constructor deferral mechanism with post-link Mach-O section patching, so dyld does not run constructors before NuttX initialization.

Changes:

• Removes the old runtime Mach-O constructor interception path.
• Adds macOS linker flags and post-build patching for Mach-O init sections.
• Maps macOS Mach-O section boundary symbols to _sinit / _einit.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
libs/libc/misc/lib_cxx_initialize.c	Uses the common _sinit / _einit constructor loop for macOS too.
arch/sim/src/sim/posix/sim_macho_init.c	Removes the previous runtime constructor-saving hack.
arch/sim/src/sim/CMakeLists.txt	Adds macOS link options and a post-build Mach-O patch command.
arch/sim/src/patch_macho_initsection.py	Adds the LIEF-based Mach-O section type patcher.
arch/sim/src/Makefile	Adds macOS linker flags and invokes the patcher in make builds.
arch/sim/include/arch.h	Adds macOS-specific _sinit / _einit asm symbol mappings.

---

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[toku-mac]

Hello. Regarding arch/sim/src/sim/CMakeLists.txt.

  add_custom_command(
    TARGET nuttx
    POST_BUILD
    COMMAND
      ${Python3_EXECUTABLE}
      ${CMAKE_CURRENT_SOURCE_DIR}/../patch_macho_initsection.py
      $<TARGET_FILE:nuttx>
    COMMENT "Patching Mach-O init section type flags")
endif()

add_custom_command(TARGET ...) can only be used in the directory where the target was created.
Since the nuttx executable is created in the top-level CMakeLists.txt, attaching a POST_BUILD command to it from here would not work.
Please use a custom target hooked into nuttx_post instead.

  add_custom_target(
    sim_patch_macho_initsection ALL
    COMMAND
      ${Python3_EXECUTABLE}
      ${CMAKE_CURRENT_SOURCE_DIR}/../patch_macho_initsection.py
      $<TARGET_FILE:nuttx>
    DEPENDS nuttx
    COMMENT "Patching Mach-O init section type flags")
  add_dependencies(nuttx_post sim_patch_macho_initsection)
endif()

[toku-mac]

about arch/sim/src/patch_macho_initsection.py.
On macOS 11 and later with Apple Silicon, binary re-signing is required.

Writing the file invalidates the ad-hoc signature that ld attached at link time, which causes the kernel to SIGKILL the process at exec.

import argparse
import subprocess
import sys

    if patched:
        fat.write(args.binary)

        if sys.platform == "darwin":
            subprocess.run(
                ["codesign", "--force", "--sign", "-", args.binary],
                check=True,
            )

    return 0

[xiaoxiang781216]

@toku-mac I have added you to my repo collaborator, please run the below command in your local nuttx git:

git remote add xiaoxiang781216 git@github.com:xiaoxiang781216/incubator-nuttx.git
git fetch xiaoxiang781216
git branch --track macos xiaoxiang781216/macos
git checkout macos
do the change you want
git commit --amend -s
git push -f xiaoxiang781216

since it's simpler to modify and update this patch by you directly.

[toku-mac]

Hello everyone.
I pushed commit a73cb17. Please confirm.

Environment

• Mac mini Apple M1
• macOS 26.5
• CLT: 26.5.0.0.1777544298
• Xcode: 26.5
• cmake: 4.3.2
• ninja: 1.13.2
• Python 3.14.5 (with lief installed)

apps branch: add_apple_cargo_cmake (commit 97716525)

Preparation

rm -rf build-debug
make distclean
cmake -S . -B build-debug -DBOARD_CONFIG=sim:nsh -GNinja
cmake --build build-debug -t menuconfig

Configure

CONFIG_SYSTEM_TIME64=y
CONFIG_FS_LARGEFILE=y
CONFIG_TLS_NELEM=16
CONFIG_DEV_URANDOM=y
CONFIG_EXAMPLES_HELLO_RUST_CARGO=y
CONFIG_EXAMPLES_HELLO_RUST_CARGO_STACKSIZE=8192
# CONFIG_COVERAGE_TOOLCHAIN is not set
CONFIG_COVERAGE_NONE=y

Build

cmake --build build-debug
...
   Compiling std_detect v0.1.5 (/Users/toku/.rustup/toolchains/nightly-2026-04-29-aarch64-apple-darwin/lib/rustlib/src/rust/library/std_detect)
   Compiling addr2line v0.25.1
   Compiling proc_macro v0.0.0 (/Users/toku/.rustup/toolchains/nightly-2026-04-29-aarch64-apple-darwin/lib/rustlib/src/rust/library/proc_macro)
   Compiling itoa v1.0.18
   Compiling pin-project-lite v0.2.17
   Compiling memchr v2.8.0
   Compiling tokio v1.52.3
   Compiling hello v0.1.0 (/Users/toku/nuttxspace/apps/examples/rust/hello)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 15.41s
[1223/1228] Linking C executable nuttx
ld: warning: -ld_classic is deprecated and will be removed in a future release
[1225/1228] Patching Mach-O init section type flags
/Users/toku/nuttxspace/nuttx/build-debug/nuttx: replacing existing signature
/Users/toku/nuttxspace/nuttx/build-debug/nuttx: valid on disk
/Users/toku/nuttxspace/nuttx/build-debug/nuttx: satisfies its Designated Requirement

Execute

./build-debug/nuttx

NuttShell (NSH) NuttX-12.13.0
nsh> help
help usage:  help [-v] [<cmd>]

    .           cmp         fdinfo      mkrd        rm          true
    [           dirname     free        mount       rmdir       truncate
    ?           df          help        mv          set         uname
    alias       dmesg       hexdump     pidof       kill        umount
    unalias     echo        losetup     poweroff    pkill       unset
    basename    env         ln          quit        sleep       uptime
    break       exec        ls          printf      usleep      watch
    cat         exit        mkdir       ps          source      xd
    cd          expr        mkfatfs     pwd         test        wait
    cp          false       mkfifo      readlink    time

Builtin Apps:
    dd                  nsh                 ostest              hello
    dumpstack           sh                  gpio                hello_rust_cargo
nsh> uname -a
NuttX 12.13.0 eae41cab13-dirty May 18 2026 10:43:05 sim sim
nsh> hello_rust_cargo
{"name":"John","age":30}
{"name":"Jane","age":25}
Deserialized: Alice is 28 years old
Pretty JSON:
{
  "name": "Alice",
  "age": 28
}

thread '<unnamed>' (540079) panicked at /Users/toku/.rustup/toolchains/nightly-2026-04-29-aarch64-apple-darwin/lib/rustlib/src/rust/library/std/src/sys/pal/unix/time.rs:107:68:
called `Result::unwrap()` on an `Err` value: Os { code: 0, kind: Uncategorized, message: "Unknown error 0" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
nsh>

The last Rust tokio-related panic I'll fix in another PR.

[xiaoxiang781216]

Hello everyone. I pushed commit a73cb17. Please confirm.

The last Rust tokio-related panic I'll fix in another PR.

@toku-mac Thank for help verifying this patch work on your machine. @yamt please review the new approach to fix macOS c++ initialization order.