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[libclang][Cygwin] Use __declspec(dllexport) for libclang on Cygwin #147122

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Merged
merged 1 commit into from
Jul 7, 2025
Merged

[libclang][Cygwin] Use __declspec(dllexport) for libclang on Cygwin #147122

merged 1 commit into from
Jul 7, 2025

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kikairoya
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This is needed for Cygwin build without -DLLVM_LINK_LLVM_DYLIB=ON, otherwise causes a linker error 'export ordinal too large'.

@kikairoya
[libclang][Cygwin] Use __declspec(dllexport) for libclang on Cygwin
4406a45 
This is needed for Cygwin build without LLVM_LINK_LLVM_DYLIB, otherwise
causes a linker error 'export ordinal too large'.
@llvmbot llvmbot added clang Clang issues not falling into any other category clang:as-a-library libclang and C++ API labels Jul 5, 2025
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llvmbot commented Jul 5, 2025

@llvm/pr-subscribers-clang

Author: Tomohiro Kashiwada (kikairoya)

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This is needed for Cygwin build without -DLLVM_LINK_LLVM_DYLIB=ON, otherwise causes a linker error 'export ordinal too large'.

Full diff: https://github.com/llvm/llvm-project/pull/147122.diff

1 Files Affected:

  • (modified) clang/include/clang-c/Platform.h (+1-1)
diff --git a/clang/include/clang-c/Platform.h b/clang/include/clang-c/Platform.h
index 67c1fff8ff783..8d341ddd6f8eb 100644
--- a/clang/include/clang-c/Platform.h
+++ b/clang/include/clang-c/Platform.h
@@ -22,7 +22,7 @@ LLVM_CLANG_C_EXTERN_C_BEGIN
 #ifndef CINDEX_NO_EXPORTS
   #define CINDEX_EXPORTS
 #endif
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN__)
   #ifdef CINDEX_EXPORTS
     #ifdef _CINDEX_LIB_
       #define CINDEX_LINKAGE __declspec(dllexport)

@kikairoya
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Before merge this, requires #147108

@github-actions GitHub Actions
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github-actions bot commented Jul 5, 2025

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command: 
git-clang-format --diff HEAD~1 HEAD --extensions h -- clang/include/clang-c/Platform.h
View the diff from clang-format here. 
diff --git a/clang/include/clang-c/Platform.h b/clang/include/clang-c/Platform.h
index 8d341ddd6..1c28ccf81 100644
--- a/clang/include/clang-c/Platform.h
+++ b/clang/include/clang-c/Platform.h
@@ -23,13 +23,13 @@ LLVM_CLANG_C_EXTERN_C_BEGIN
   #define CINDEX_EXPORTS
 #endif
 #if defined(_WIN32) || defined(__CYGWIN__)
-  #ifdef CINDEX_EXPORTS
-    #ifdef _CINDEX_LIB_
-      #define CINDEX_LINKAGE __declspec(dllexport)
-    #else
-      #define CINDEX_LINKAGE __declspec(dllimport)
-    #endif
-  #endif
+#ifdef CINDEX_EXPORTS
+#ifdef _CINDEX_LIB_
+#define CINDEX_LINKAGE __declspec(dllexport)
+#else
+#define CINDEX_LINKAGE __declspec(dllimport)
+#endif
+#endif
 #elif defined(CINDEX_EXPORTS) && defined(__GNUC__)
   #define CINDEX_LINKAGE __attribute__((visibility("default")))
 #endif

@kikairoya
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git clang-format makes reformat below, should it be applied?

diff --git a/clang/include/clang-c/Platform.h b/clang/include/clang-c/Platform.h
index 8d341ddd6f8e..1c28ccf81981 100644
--- a/clang/include/clang-c/Platform.h
+++ b/clang/include/clang-c/Platform.h
@@ -23,13 +23,13 @@ LLVM_CLANG_C_EXTERN_C_BEGIN
   #define CINDEX_EXPORTS
 #endif
 #if defined(_WIN32) || defined(__CYGWIN__)
-  #ifdef CINDEX_EXPORTS
-    #ifdef _CINDEX_LIB_
-      #define CINDEX_LINKAGE __declspec(dllexport)
-    #else
-      #define CINDEX_LINKAGE __declspec(dllimport)
-    #endif
-  #endif
+#ifdef CINDEX_EXPORTS
+#ifdef _CINDEX_LIB_
+#define CINDEX_LINKAGE __declspec(dllexport)
+#else
+#define CINDEX_LINKAGE __declspec(dllimport)
+#endif
+#endif
 #elif defined(CINDEX_EXPORTS) && defined(__GNUC__)
   #define CINDEX_LINKAGE __attribute__((visibility("default")))
 #endif

@mstorsjo
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mstorsjo commented Jul 5, 2025

Before merge this, requires #147108

Can you elaborate on why this is needed - what happens without it - wouldn't that issue be happening already now in regular win32 builds so far?

@kikairoya
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Before merge this, requires #147108

Can you elaborate on why this is needed - what happens without it - wouldn't that issue be happening already now in regular win32 builds so far?

The linker reports undefined reference to clang_install_aborting_llvm_fatal_error_handler, and cannot run testsuite.

FAILED: tools/clang/unittests/libclang/CrashTests/libclangCrashTests.exe
: && /usr/bin/g++.exe  -pipe -Wa,-mbig-obj -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -fno-common -Woverloaded-virtual -O2 -DNDEBUG -Wl,--enable-auto-import -Wl,--stack,16777216    -Wl,--gc-sections tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o -o tools/clang/unittests/libclang/CrashTests/libclangCrashTests.exe -Wl,--out-implib,tools/clang/unittests/libclang/CrashTests/liblibclangCrashTests.dll.a -Wl,--major-image-version,0,--minor-image-version,0  lib/libLLVMSupport.a  lib/libllvm_gtest_main.a  lib/libllvm_gtest.a  lib/libclang.dll.a  lib/libLLVMSupport.a  -lrt  -ldl  -lm  /usr/lib/libz.dll.a  /usr/lib/libzstd.dll.a  lib/libLLVMDemangle.a  -lpthread && :
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x21d): undefined reference to `clang_install_aborting_llvm_fatal_error_handler'
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x61f): undefined reference to `clang_install_aborting_llvm_fatal_error_handler'
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x624): undefined reference to `clang_uninstall_llvm_fatal_error_handler'
collect2: エラー: ld はステータス 1 で終了しました

For regular Win32 targets, this unittest is disabled.

llvm-project/clang/unittests/CMakeLists.txt

Lines 98 to 102 in 4406a45

# FIXME: libclang unit tests are disabled on Windows due
# to failures, mostly in libclang.VirtualFileOverlay_*.
if(NOT WIN32 AND CLANG_TOOL_LIBCLANG_BUILD)
add_subdirectory(libclang)
endif()

@mstorsjo
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mstorsjo commented Jul 6, 2025

Before merge this, requires #147108

Can you elaborate on why this is needed - what happens without it - wouldn't that issue be happening already now in regular win32 builds so far?

The linker reports undefined reference to clang_install_aborting_llvm_fatal_error_handler, and cannot run testsuite.

FAILED: tools/clang/unittests/libclang/CrashTests/libclangCrashTests.exe
: && /usr/bin/g++.exe  -pipe -Wa,-mbig-obj -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -fno-common -Woverloaded-virtual -O2 -DNDEBUG -Wl,--enable-auto-import -Wl,--stack,16777216    -Wl,--gc-sections tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o -o tools/clang/unittests/libclang/CrashTests/libclangCrashTests.exe -Wl,--out-implib,tools/clang/unittests/libclang/CrashTests/liblibclangCrashTests.dll.a -Wl,--major-image-version,0,--minor-image-version,0  lib/libLLVMSupport.a  lib/libllvm_gtest_main.a  lib/libllvm_gtest.a  lib/libclang.dll.a  lib/libLLVMSupport.a  -lrt  -ldl  -lm  /usr/lib/libz.dll.a  /usr/lib/libzstd.dll.a  lib/libLLVMDemangle.a  -lpthread && :
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x21d): undefined reference to `clang_install_aborting_llvm_fatal_error_handler'
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x61f): undefined reference to `clang_install_aborting_llvm_fatal_error_handler'
/usr/lib/gcc/x86_64-pc-cygwin/15/../../../../x86_64-pc-cygwin/bin/ld: tools/clang/unittests/libclang/CrashTests/CMakeFiles/libclangCrashTests.dir/LibclangCrashTest.cpp.o:LibclangCrashTest.cpp:(.text+0x624): undefined reference to `clang_uninstall_llvm_fatal_error_handler'
collect2: エラー: ld はステータス 1 で終了しました

For regular Win32 targets, this unittest is disabled.

llvm-project/clang/unittests/CMakeLists.txt

Lines 98 to 102 in 4406a45

# FIXME: libclang unit tests are disabled on Windows due
# to failures, mostly in libclang.VirtualFileOverlay_*.
if(NOT WIN32 AND CLANG_TOOL_LIBCLANG_BUILD)
add_subdirectory(libclang)
endif()

Thanks, that explains why this hasn't been noticed before!

mstorsjo
mstorsjo approved these changes Jul 6, 2025
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LGTM, thanks.

But we should wait for #147108 to land first before merging this.

@mstorsjo mstorsjo merged commit 122afae into llvm:main Jul 7, 2025
11 of 12 checks passed
@kikairoya kikairoya deleted the cygwin-libclang-dllexport branch July 7, 2025 21:07
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