https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99741
Bug ID: 99741 Summary: dllexport attribute is not compatible with c99 inline Product: gcc Version: 10.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: aladjev.andrew at gmail dot com Target Milestone: --- Created attachment 50466 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50466&action=edit fit.tar.gz Hello, please review the following cmake issue here https://gitlab.kitware.com/cmake/cmake/-/issues/21940#note_925715. I am trying to create cross platform application, than I need to compile it using MSVC. MSVC requires mandatory dllexport and dllimport attributes for all functions including C99 inline functions. Clang is completely ignoring these attributes in GNU env and it is always successful https://github.com/llvm/llvm-project/commit/606bd6dcc547cf2f9fd7387321db79419bf60041. GCC ignores only dllimport attribute, but fails with dllexport attribute. Please review simplified project: a1.h, a1.c, a2.c and CMakeLists.txt attached. You can try to build it on windows using: CC="gcc" cmake -G "Unix Makefiles" -DCMAKE_VERBOSE_MAKEFILE=1 . && make CC="clang" cmake -G "Unix Makefiles" -DCMAKE_VERBOSE_MAKEFILE=1 . && make GCC provides error: multiple definition of func. I can't understand the reason of this error: maybe dllexport converted C99 inline declaration into C89? Workaround for this issue is to remove dllexport attribute for windows platform + gcc on makefile generator layer (cmake/etc). PS this issue is indirectly related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90161