Clarify parallel scheduler build

CMakeLists.txt

@@ -297,7 +297,7 @@ if(STDEXEC_BUILD_TESTS)
   endif()
 
   # These headers are Linux-only.
-  if(WIN32)
+  if(NOT LINUX)
     set_source_files_properties(
       include/exec/linux/io_uring_context.hpp
       include/exec/linux/memory_mapped_region.hpp
@@ -306,6 +306,13 @@ if(STDEXEC_BUILD_TESTS)
       include/exec/linux/detail/safe_file_descriptor.hpp
       PROPERTIES SKIP_LINTING ON)
   endif()
+
+  # These headers are macOS-only.
+  if(NOT APPLE)
+    set_source_files_properties(
+      include/exec/libdispatch_queue.hpp
+      PROPERTIES SKIP_LINTING ON)
+  endif()
 endif()
 
 # Declare the public include directories
@@ -349,6 +356,10 @@ if(NOT STDEXEC_NAMESPACE STREQUAL "stdexec")
                                      STDEXEC_NAMESPACE=${STDEXEC_NAMESPACE})
 endif()
 
+if (NOT STDEXEC_BUILD_PARALLEL_SCHEDULER)
+  target_compile_definitions(stdexec INTERFACE STDEXEC_PARALLEL_SCHEDULER_HEADER_ONLY)
+endif()
+
 option(STDEXEC_ENABLE_EXTRA_TYPE_CHECKING
        "Enable extra type checking that is costly at compile-time" OFF)
 if(STDEXEC_ENABLE_EXTRA_TYPE_CHECKING)
@@ -580,13 +591,16 @@ if(STDEXEC_BUILD_PARALLEL_SCHEDULER)
                               /Zc:preprocessor /Zc:externConstexpr>)
   target_link_libraries(parallel_scheduler PUBLIC stdexec)
 
-  add_library(STDEXEC::parallel_scheduler ALIAS parallel_scheduler)
-  add_library(system_context ALIAS parallel_scheduler)
-  add_library(STDEXEC::system_context ALIAS parallel_scheduler)
-
   set(stdexec_export_targets ${stdexec_export_targets} parallel_scheduler)
+else()
+  add_library(parallel_scheduler INTERFACE)
+  target_link_libraries(parallel_scheduler INTERFACE stdexec)
 endif()
 
+add_library(STDEXEC::parallel_scheduler ALIAS parallel_scheduler)
+add_library(system_context ALIAS parallel_scheduler)
+add_library(STDEXEC::system_context ALIAS parallel_scheduler)
+
 option(STDEXEC_ENABLE_IO_URING
        "Enable the use of the io_uring scheduler on Linux" OFF)
 

examples/CMakeLists.txt

@@ -47,6 +47,9 @@ function(def_example example)
                                                          # emitted from stdlib
                                                          # headers, why?
       $<$<CXX_COMPILER_ID:Clang>:-Wno-gnu-line-marker>)
+  target_compile_definitions(${target} PRIVATE
+    $<$<PLATFORM_ID:Windows>:NOMINMAX>
+  )
   target_link_libraries(
     ${target}
     PRIVATE STDEXEC::stdexec stdexec_executable_flags stdexec_example_settings
@@ -86,15 +89,8 @@ foreach(example ${stdexec_examples})
   def_example(${example})
 endforeach()
 
-if(STDEXEC_BUILD_PARALLEL_SCHEDULER)
-  target_link_libraries(example.hello_world PUBLIC STDEXEC::parallel_scheduler)
-  target_link_libraries(example.sudoku PRIVATE STDEXEC::parallel_scheduler)
-else()
-  target_compile_definitions(example.hello_world
-                             PRIVATE STDEXEC_PARALLEL_SCHEDULER_HEADER_ONLY)
-  target_compile_definitions(example.sudoku
-                             PRIVATE STDEXEC_PARALLEL_SCHEDULER_HEADER_ONLY)
-endif()
+target_link_libraries(example.hello_world PUBLIC STDEXEC::parallel_scheduler)
+target_link_libraries(example.sudoku PRIVATE STDEXEC::parallel_scheduler)
 
 if(STDEXEC_ENABLE_CUDA)
   add_subdirectory(nvexec)
@@ -132,4 +128,8 @@ if(STDEXEC_ENABLE_ASIO)
     example.benchmark.asio_thread_pool
     PRIVATE stdexec_example_settings STDEXEC::asioexec
             $<TARGET_NAME_IF_EXISTS:TBB::tbb>)
+  target_compile_definitions(
+    example.benchmark.asio_thread_pool
+    PRIVATE $<$<PLATFORM_ID:Windows>:NOMINMAX>
+  )
 endif()

examples/benchmark/asio_thread_pool.cpp

@@ -14,8 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include "./common.hpp"
 #include <exec/asio/asio_thread_pool.hpp>
+
+#include "./common.hpp"
 #include <exec/start_detached.hpp>
 
 struct RunThread

examples/scope.cpp

@@ -100,7 +100,7 @@ auto main() -> int
 
   {
     sender auto nest = scope.nest(begin);
-    auto        op   = connect(std::move(nest), noop_receiver{});
+    auto        op   = stdexec::connect(std::move(nest), noop_receiver{});
     (void) op;
   }
   sync_wait(scope.on_empty());

include/exec/libdispatch_queue.hpp

@@ -16,30 +16,53 @@
 
 #pragma once
 
-#if __has_include(<dispatch/dispatch.h>)
+#include "../stdexec/__detail/__config.hpp"
 
-#  include <stdexec/execution.hpp>
-
-#  if STDEXEC_USE_MODULES() && !defined(STDEXEC_IN_MODULE_PURVIEW)
+#if STDEXEC_USE_MODULES() && !defined(STDEXEC_IN_MODULE_PURVIEW)
+import std;
 import stdexec;
-#  else
+#else
+#  include "../stdexec/__detail/__bulk.hpp"
+#  include "../stdexec/__detail/__domain.hpp"
+#  include "../stdexec/__detail/__env.hpp"
+#  include "../stdexec/__detail/__execution_fwd.hpp"
+#  include "../stdexec/__detail/__execution_legacy.hpp"  // IWYU pragma: keep
+#  include "../stdexec/__detail/__operation_states.hpp"
+#  include "../stdexec/__detail/__receivers.hpp"
+#  include "../stdexec/__detail/__schedulers.hpp"
+#  include "../stdexec/__detail/__stop_token.hpp"
+#  include "../stdexec/__detail/__transform_sender.hpp"
+
+#  if !STDEXEC_USE_MODULES()
+#    include <algorithm>
+#    include <atomic>
+#    include <concepts>
+#    include <cstddef>
+#    include <cstdint>
+#    include <exception>
+#    include <tuple>
+#    include <type_traits>
+#    include <utility>
+#    include <variant>
+#    include <vector>
+#  endif
+#endif
+
+#include "completion_signatures.hpp"
+#include "sender_for.hpp"
+
+#if !defined(STDEXEC_IN_MODULE_PURVIEW)
 // TODO: This is needed for libdispatch to compile with GCC. Need to look for
 // workaround.
-#    ifndef __has_feature
-#      define __has_feature(x) false
-#    endif
-#    ifndef __has_extension
-#      define __has_extension(x) false
-#    endif
-
-#    include "completion_signatures.hpp"
-#    include "sender_for.hpp"
-
-#    if !STDEXEC_USE_MODULES()
-#      include <dispatch/dispatch.h>
-#      include <utility>
-#      include <vector>
-#    endif
+#  ifndef __has_feature
+#    define __has_feature(x) false
+#  endif
+#  ifndef __has_extension
+#    define __has_extension(x) false
+#  endif
+
+#  include <dispatch/dispatch.h>
+#endif
 
 namespace experimental::execution
 {
@@ -597,6 +620,3 @@ namespace experimental::execution
 }  // namespace experimental::execution
 
 namespace exec = experimental::execution;
-
-#  endif  // !STDEXEC_USE_MODULES() || defined(STDEXEC_IN_MODULE_PURVIEW)
-#endif    // __has_include(<dispatch/dispatch.h>)

include/exec/trampoline_scheduler.hpp

@@ -177,6 +177,13 @@ namespace experimental::execution
             {
               // Exceeded recursion limit.
 
+              // GCC may warn that this stores the address of a local operation
+              // state into thread-local storage. That is a false positive: an
+              // enclosing origin schedule frame owns the state and drains the
+              // queue before this operation state's lifetime ends.
+              STDEXEC_PRAGMA_PUSH()
+              STDEXEC_PRAGMA_IGNORE_GNU("-Wdangling-pointer")
+
               // push this recursive schedule to list tail
               __prev_ = std::exchange(__current_state->__tail_, static_cast<__opstate_base*>(this));
               if (__prev_ != nullptr)
@@ -189,6 +196,8 @@ namespace experimental::execution
                 // was empty
                 __current_state->__head_ = static_cast<__opstate_base*>(this);
               }
+
+              STDEXEC_PRAGMA_POP()
             }
           }
         }

include/stdexec/__detail/__parallel_scheduler_replacement_api.hpp

@@ -36,9 +36,7 @@ import stdexec;
 namespace STDEXEC::parallel_scheduler_replacement
 {
   //! Get the backend for the parallel scheduler.
-  //! Users might replace this function.
   STDEXEC_MODULE_EXPORT
-  STDEXEC_ATTRIBUTE(weak)
   auto query_parallel_scheduler_backend() -> std::shared_ptr<parallel_scheduler_backend>;
 
   //! The type of a factory that can create `parallel_scheduler_backend`

test/CMakeLists.txt

@@ -114,8 +114,7 @@ set_target_properties(
 target_include_directories(common_test_settings
                            INTERFACE "${CMAKE_CURRENT_LIST_DIR}")
 target_compile_definitions(
-  common_test_settings INTERFACE STDEXEC_NAMESPACE=std::execution
-                                 $<$<PLATFORM_ID:Windows>:NOMINMAX>)
+  common_test_settings INTERFACE $<$<PLATFORM_ID:Windows>:NOMINMAX>)
 target_compile_options(
   common_test_settings
   INTERFACE
@@ -163,7 +162,8 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL Clang OR CMAKE_CXX_COMPILER_ID STREQUAL GNU)
 endif()
 target_link_libraries(
   test.stdexec
-  PUBLIC STDEXEC::stdexec stdexec_executable_flags Catch2::Catch2WithMain
+  PUBLIC STDEXEC::stdexec STDEXEC::parallel_scheduler stdexec_executable_flags
+         Catch2::Catch2WithMain
   PRIVATE common_test_settings)
 
 if(STDEXEC_BUILD_PARALLEL_SCHEDULER)

test/exec/asio/test_asio_thread_pool.cpp

@@ -14,12 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <exec/asio/asio_thread_pool.hpp>
 
 #include <catch2/catch_all.hpp>
 
 #include <stdexec/execution.hpp>
 
-#include <exec/asio/asio_thread_pool.hpp>
 #include <exec/asio/use_sender.hpp>
 #include <exec/inline_scheduler.hpp>
 #include <exec/static_thread_pool.hpp>

test/exec/test_materialize.cpp

@@ -124,7 +124,7 @@ namespace
       set_equivalent<completion_signatures_of_t<decltype(sndr)>,
                      completion_signatures<set_value_t(set_error_t, noncopyable_error&)>>);
 
-    auto op = connect(std::move(sndr), error_receiver{&error, &called});
+    auto op = ex::connect(std::move(sndr), error_receiver{&error, &called});
     start(op);
     CHECK(called);
   }

test/run_loop_finish_repro.cpp

@@ -2,7 +2,7 @@
 
 #include <thread>
 
-namespace ex = STDEXEC_NAMESPACE;
+namespace ex = STDEXEC;
 
 void run_once()
 {

test/stdexec/schedulers/test_parallel_scheduler.cpp

@@ -15,9 +15,10 @@
  */
 #include <catch2/catch_all.hpp>
 
-#define STDEXEC_PARALLEL_SCHEDULER_HEADER_ONLY 1
 #include <stdexec/execution.hpp>
 
+#include <stdexec/__detail/__parallel_scheduler_default_impl.hpp>
+
 #include <exec/async_scope.hpp>
 #include <exec/inline_scheduler.hpp>
 #include <exec/static_thread_pool.hpp>