modules in shared libraries

1. [GCC] initializer for module is hidden with -fvisibility=hidden
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105397

2. [Clang] initializer for module is not dllexported when targeting MinGW
mstorsjo/llvm-mingw#421

3. [Clang] not strong ownership model when targeting MSVC ABI
llvm/llvm-project#89781

4. [Clang] module variables are not dllimported
llvm/llvm-project#87887

5. [DLL] module functions are not dllimported causing indirect function call
https://stackoverflow.com/a/74444920
https://developercommunity.visualstudio.com/t/10202062
https://gitlab.kitware.com/cmake/cmake/-/issues/25539

.gitignore

@@ -11,3 +11,10 @@ CMakeUserPresets.json
 *.pcm
 *.gcm
 *.exe
+*.exp
+*.lib
+*.dll
+*.pdb
+*.a
+*.so
+*.dylib

CMakeLists.txt

@@ -28,3 +28,4 @@ add_subdirectory(module-partition)
 add_subdirectory(module-impl)
 # add_subdirectory(header-unit)
 add_subdirectory(import-std)
+add_subdirectory(shared-lib)

shared-lib/CMakeLists.txt

@@ -0,0 +1,48 @@
+cmake_minimum_required(VERSION 3.28)
+project(shared-lib)
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_BUILD_RPATH_USE_ORIGIN ON)
+set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
+set(CMAKE_C_VISIBILITY_PRESET hidden)
+set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+
+# https://gitlab.kitware.com/cmake/cmake/-/issues/25875
+if(CMAKE_VISIBILITY_INLINES_HIDDEN AND CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND WIN32)
+  if(CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC")
+    add_compile_options(/Zc:dllexportInlines-)
+  else()
+    add_compile_options(-Xclang=-fno-dllexport-inlines)
+  endif()
+endif()
+
+add_library(hello SHARED)
+target_sources(hello
+  PRIVATE
+    impl.cpp
+  PUBLIC FILE_SET HEADERS FILES
+    hello.hpp
+  PUBLIC FILE_SET CXX_MODULES FILES
+    hello.ixx
+)
+
+# https://github.com/mstorsjo/llvm-mingw/issues/421
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND MINGW)
+  # -fms-extensions is disabled by default for MinGW
+  target_link_options(hello PRIVATE LINKER:-Xlink=-export:_ZGIW5hello)
+endif()
+
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105397
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  target_link_options(hello INTERFACE LINKER:--wrap=_ZGIW5hello)
+endif()
+
+add_executable(${PROJECT_NAME})
+target_sources(${PROJECT_NAME}
+  PRIVATE
+    main.cpp
+)
+target_link_libraries(${PROJECT_NAME} PUBLIC hello)
+
+add_test(NAME ${PROJECT_NAME} COMMAND ${PROJECT_NAME})

shared-lib/Makefile.clang

@@ -0,0 +1,12 @@
+hello.exe: main.cpp libhello.so hello.pcm
+	clang++ -std=c++20 -g -fprebuilt-module-path=. main.cpp -o hello.exe libhello.so -Wl,-rpath,.
+
+libhello.so hello.pcm: hello.ixx hello.hpp impl.cpp
+	clang++ -std=c++20 -g -fprebuilt-module-path=. -fmodule-output -shared -fPIC \
+	-fvisibility=hidden -fvisibility-inlines-hidden \
+	-x c++-module hello.ixx -x c++ impl.cpp -o libhello.so
+
+clean:
+	-rm  *.pcm *.o *.exe *.so
+	-del *.pcm *.o *.exe *.so
+

shared-lib/Makefile.clang-mingw

@@ -0,0 +1,15 @@
+hello.exe: main.cpp hello.dll hello.pcm
+	$(PREFIX)clang++ -fms-extensions -std=c++20 -fprebuilt-module-path=. \
+	-g -gcodeview -Wl,--pdb=hello.exe.pdb \
+	main.cpp -o hello.exe -L. -lhello
+
+hello.dll hello.pcm: hello.ixx hello.hpp impl.cpp
+	$(PREFIX)clang++ -fms-extensions -std=c++20 -fprebuilt-module-path=. -fmodule-output -shared \
+	-fvisibility=hidden -fvisibility-inlines-hidden \
+	-g -gcodeview -Wl,--pdb=hello.dll.pdb \
+	-x c++-module hello.ixx -x c++ impl.cpp -o hello.dll
+
+clean:
+	-rm  *.pcm *.o *.obj *.exe *.exp *.lib *.dll *.pdb
+	-del *.pcm *.o *.obj *.exe *.exp *.lib *.dll *.pdb
+

shared-lib/Makefile.clang-win32

@@ -0,0 +1,16 @@
+hello.exe: main.cpp hello.lib hello.pcm
+	clang++ -std=c++20 -fprebuilt-module-path=. \
+	-Xclang -fno-dllexport-inlines \
+	-g -gcodeview -Wl,/PDB:hello.exe.pdb -Wl,/INCREMENTAL:NO \
+	main.cpp -o hello.exe hello.lib -Wl,/NOIMPLIB
+
+hello.dll hello.lib hello.pcm: hello.ixx hello.hpp impl.cpp
+	clang++ -std=c++20 -fprebuilt-module-path=. -fmodule-output -shared \
+	-Xclang -fno-dllexport-inlines \
+	-g -gcodeview -Wl,/PDB:hello.dll.pdb -Wl,/INCREMENTAL:NO \
+	-x c++-module hello.ixx -x c++ impl.cpp -o hello.dll
+
+clean:
+	-rm  *.pcm *.o *.obj *.exe *.exp *.lib *.dll *.pdb
+	-del *.pcm *.o *.obj *.exe *.exp *.lib *.dll *.pdb
+

shared-lib/Makefile.gcc

@@ -0,0 +1,11 @@
+hello.exe: main.cpp libhello.so gcm.cache/hello.gcm
+	g++ -std=c++20 -fmodules-ts -g main.cpp -o hello.exe libhello.so -Wl,-rpath,. -Wl,--wrap=_ZGIW5hello
+
+libhello.so gcm.cache/hello.gcm: hello.ixx hello.hpp impl.cpp
+	g++ -std=c++20 -fmodules-ts -g -shared -fPIC \
+	-fvisibility=hidden -fvisibility-inlines-hidden \
+	-x c++ hello.ixx impl.cpp -o libhello.so
+
+clean:
+	rm -rf *.gcm gcm.* *.o *.exe *.so
+

shared-lib/Makefile.msvc

@@ -0,0 +1,10 @@
+hello.exe: main.cpp hello.lib hello.ifc
+	cl /nologo /EHsc /std:c++20 main.cpp hello.lib /Fe:hello /Zi /link /PDB:hello.exe.pdb /INCREMENTAL:NO /NOIMPLIB /NOEXP
+
+hello.dll hello.lib hello.ifc: hello.ixx hello.hpp impl.cpp
+	cl /nologo /EHsc /std:c++20 /LD hello.ixx impl.cpp /Zi /link /PDB:hello.dll.pdb
+
+clean:
+	-del *.ifc *.obj *.exe *.exp *.lib *.dll *.pdb
+	-rm  *.ifc *.obj *.exe *.exp *.lib *.dll *.pdb
+

shared-lib/hello.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#if defined(_WIN32) || defined(__CYGWIN__)
+# define EXPORT __declspec(dllexport)
+# define IMPORT __declspec(dllimport)
+#else
+# define EXPORT __attribute__((visibility("default")))
+# define IMPORT __attribute__((visibility("default")))
+#endif
+
+#if defined(IMPL)
+#include <iostream>
+extern "C++" EXPORT void is_direct_call_to_gmf(void(*f)())
+{
+    std::cout << __func__ << "? " << (f == (void(*)())&is_direct_call_to_gmf ? "Yes" : "No") << std::endl;
+}
+#elif defined(DECL)
+IMPORT void is_direct_call_to_gmf(void(*f)());
+#endif

shared-lib/hello.ixx

@@ -0,0 +1,36 @@
+module;
+
+#include <source_location>
+//#define IMPL
+#include "hello.hpp"
+
+export module hello;
+
+// https://github.com/mstorsjo/llvm-mingw/issues/421
+#if defined(__clang__) && defined(__MINGW32__)
+# pragma comment(linker, "-export:_ZGIW5hello") //-fms-extensions
+#endif
+
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105397
+#if defined(__GNUC__) && !defined(__clang__)
+extern "C" EXPORT void __wrap__ZGIW5hello() __attribute__((alias("_ZGIW5hello"))); //-Wl,--wrap=_ZGIW5hello
+#endif
+
+// https://developercommunity.visualstudio.com/t/10651933
+export EXPORT auto gploc = new auto([] { return std::source_location::current(); }());
+
+export EXPORT void hello(const std::source_location* ploc = nullptr);
+export EXPORT void is_direct_call_to_hello(void(*f)(const std::source_location*));
+
+export class EXPORT Hello
+{
+public:
+    auto hello()
+    {
+        return inline_hello();
+    }
+
+    inline void inline_hello()
+    {
+    }
+};

shared-lib/impl.cpp

@@ -0,0 +1,22 @@
+module;
+
+#include <iostream>
+#include <source_location>
+
+#define IMPL
+#include "hello.hpp"
+
+module hello;
+
+void hello(const std::source_location* ploc)
+{
+    // https://developercommunity.visualstudio.com/t/10651933
+    const auto& loc = ploc ? *ploc : [] { return std::source_location::current(); }();
+    std::cout << loc.file_name() << '(' << loc.line() << ')' << ':' << ' '
+              << "Hello, World!" << std::endl;
+}
+
+void is_direct_call_to_hello(void(*f)(const std::source_location*))
+{
+    std::cout << __func__ << "? " << (f == &hello ? "Yes" : "No") << std::endl;
+}

shared-lib/main.cpp

@@ -0,0 +1,25 @@
+#define DECL
+#include "hello.hpp"
+
+import hello;
+
+// https://github.com/llvm/llvm-project/issues/87887
+#if defined(__clang__) && defined(_WIN32) && !defined(__MINGW32__)
+extern "C" decltype(gploc)& __imp_gploc;
+// https://github.com/llvm/llvm-project/issues/89781
+// #pragma comment(linker, "/ALTERNATENAME:__imp_gploc=__imp_?gploc@@3PEAUsource_location@std@@EA::<!hello>")
+#pragma comment(linker, "/ALTERNATENAME:__imp_gploc=__imp_?gploc@@3PEAUsource_location@std@@EA")
+#define gploc __imp_gploc
+#endif
+
+int main()
+{
+    hello();
+    hello(gploc);
+
+    Hello{}.hello();
+    Hello{}.inline_hello();
+
+    is_direct_call_to_hello(&hello);
+    is_direct_call_to_gmf((void(*)())&is_direct_call_to_gmf);
+}