How to link libgomp statically when linking other libraries dynamically? - c++

Question

I am trying to build an image processing program written in C++ that depends on the following libraries using MinGW + MSYS (with GCC4.8.1) that I downloaded from www.mingw.org/ on a Windows 8 64bit computer
LibJPEG
BLAS and LAPACK
Armadillo
OpenMP
I have successfully compiled all the source code files (with -fopenmp flag of course), then I linked with the following statement:
g++ -o ./build/rspfitter {a list of .o files}
-L{paths to libraries} -ljpeg -lopenblas -lgomp -lpthread
The executable was correctly produced. However, it asks for the following dlls:
libgomp-1.dll
libpthread-2.dll
pthreadGC2.dll
I think it might a better idea to link libgomp and libpthread statically, so that I can minimize the number of dlls I need to deploy my program with (the above three dlls are not the only ones the program depends on). So I tried to link only libgomp and libpthread statically with the following command:
g++ -o ./build/rspfitter {a list of .o files}
-L{paths to libraries} -ljpeg -lopenblas -Wl,-static -lgomp -lpthread
But this time it fails with the following error message:
d:/mingw/bin/../lib/gcc/mingw32/4.8.1\libgomp.a(env.o):(.text.startup+0xbfe):
undefined reference to `_imp__pthread_attr_init'
d:/mingw/bin/../lib/gcc/mingw32/4.8.1\libgomp.a(env.o):(.text.startup+0xc13):
undefined reference to `_imp__pthread_attr_setdetachstate'
d:/mingw/bin/../lib/gcc/mingw32/4.8.1\libgomp.a(env.o):(.text.startup+0x3c):
undefined reference to `_imp__pthread_attr_setstacksize'
d:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe:
d:/mingw/bin/../lib/gcc/mingw32/4.8.1\libgomp.a(env.o): bad reloc
address 0x0 in section `.ctors'
d:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe:
final link failed: Invalid operation
Then I tried to execute the exact same compiling and linking commands using the MinGW + GCC 4.8.1 environment that was installed together with CodeLite. It fails again with different error messages：
./tmp/hshfitcmdline.o:hshfitcmdline.cpp:(.text.unlikely+0x105):
undefined reference to `_Unwind_Resume'
./tmp/hshfitcmdline.o:hshfitcmdline.cpp:(.text$_ZN9NormalMapD1Ev[__ZN9NormalMapD1Ev]+0xb4):
undefined reference to `_Unwind_Resume'
d:/mingw-4.8.1/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe:
./tmp/hshfitcmdline.o: bad reloc address 0xb4 in section
`.text$_ZN9NormalMapD1Ev[__ZN9NormalMapD1Ev]'
d:/mingw-4.8.1/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe:
final link failed: Invalid operation collect2.exe: error: ld returned
1 exit status make: *** [build/rspfitter] Error 1
I confirmed that the file "libgomp.a"/"libgomp.dll.a" was present on the [MinGW dir]/lib/gcc/mingw32/4.8.1/ for both installations of MinGW. However, they are of different sizes! In installation downloaded from MinGW.org, 'libgomp.a' is of 86kb, and "libgomp.dll.a" is of 87kb; In the CodeLite installation, however, the sizes are 74kB and 148Kb respectively.
Now I am wondering:
What could be the cause of the error messages given by the two MinGW systems? Could it be that the statically libraries that I downloaded from MinGW are corrputed? But dynamically linking was perfectly fine on both systems.
How on earth can I correctly link libgomp statically?
Thanks

Answer 1

To link libgomp statically you can do
ln -s `g++ --print-file-name=libgomp.a` && \
g++ foo.o -static-libgcc -static-libstdc++ -L. -o foo -fopenmp -ljpeg -lopenblas
However your executable will still depend on a pthread dll. The reason you are getting the error is that libc is still linking dynamically. To fix this you have to link libc statically as well
ln -s `g++ --print-file-name=libpthread.a` && \
ln -s `g++ --print-file-name=libc.a` && \
g++ foo.o -static-libgcc -static-libstdc++ -L. -o foo -fopenmp -ljpeg -lopenblas
However, if openblas or jpeg libraries depend on libc then there will likely still be undefined references.