CODEWITHSUNDEEP
cmake32bit-64bitmingw-w64
nop_0x00
nop_0x00

Reputation: 33

Building 32Bit and 64Bit application uitilizing mingw-w64 and cmake

I need to build a shared library on windows (dll) in 32bit and 64bit.
The build is controlled with cmake, the compiler is mingw64

This is my cmake file:

#64Bit Build (works fine)
ADD_LIBRARY(mylib SHARED mylib.c)
SET_TARGET_PROPERTIES(mylib PROPERTIES PREFIX "")
target_link_options(mylib PUBLIC -Wl,--exclude-all-symbols -s -Wl,--gc-sections -Wl,-Map=output.map )

#32Bit Build (linking issues)
ADD_LIBRARY(mylib32 SHARED mylib.c)
SET_TARGET_PROPERTIES(mylib32 PROPERTIES PREFIX "" COMPILE_FLAGS "-m32" LINK_FLAGS "-m32")
target_link_options(mylib32 PUBLIC --verbose -Wl,--exclude-all-symbols -s -Wl,--gc-sections -Wl,-Map=output.map)

I get a lot of complaints during linking due to 32Bit incomatibility of many linked libraries. I can reduce the amount of complaints, when I am specifically add 32Bit libraries to the search path like this:

target_link_options(mylib32 PUBLIC --verbose -Wl,--exclude-all-symbols -s -Wl,--gc-sections -Wl,-Map=output.map -L/msys64/mingw32/lib -L/msys64/mingw32/i686-w64-mingw32/lib -L/msys64/mingw32/lib/gcc/i686-w64-mingw32/10.3.0)

But there are still some incompatibilities left: like the dllcrt.a which is always linked from the 64Bit mingw path, which seems kind of hard coded into gcc/ld.

I even tried to use an empty spec fiel, which gave nor results: target_link_options(mylib32 PUBLIC -specs=myspe --verbose -Wl,--exclude-all-symbols -s -Wl,--gc-sections -Wl,-Map=output.map -L/msys64/mingw32/lib -L/msys64/mingw32/i686-w64-mingw32/lib -L/msys64/mingw32/lib/gcc/i686-w64-mingw32/10.3.0)

Typical error message I get:

C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: i386:x86-64 architecture of input file `C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.3.0/../../../../x86_64-w64-mingw32/lib/dllcrt2.o' is incompatible with i386 output

Upvotes: 0

Views: 1669

Answers (1)

nop_0x00
nop_0x00

Reputation: 33

I just figured out a solution for my case:

the crt* stuff is startup code, which is not needed in the case of libraries. So I added the -nostartfiles flag, and my library links fine. I guess in case off an application one can probably link the 32bit startfiles manualy as a workaround.

SET_TARGET_PROPERTIES(amprio_seednkey32 PROPERTIES PREFIX "" COMPILE_FLAGS "-m32 -nostartfiles" LINK_FLAGS "-m32 -nostartfiles")

Anyhow, this all feels like a dirty Workaround, I still wonder what is the best way to link 32Bit and 64Bit using mingw-w64.

Upvotes: 0

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