multiple definition of `DllMainCRTStartup@12' while building glew on windows with mingw32

Question

I followed this topic: Building glew on windows with mingw but something went wrong here:

gcc -shared -Wl,-soname,libglew32.dll -Wl,--out-implib,lib/libglew32.dll.a -o lib/glew32.dll src/glew.o -L/mingw/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lkernel32

I get this error:

C:\MinGW\dev_lib\glew-2.0.0>gcc -shared -Wl,-soname,libglew32.dll -Wl,--out-implib,lib/libglew32.dll.a -o lib/glew32.dll src/glew.o -L/mingw/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lkernel32 src/glew.o:glew.c:(.text+0x28f80): multiple definition of `DllMainCRTStartup@12' c:/mingw/bin/../lib/gcc/mingw32/4.9.3/../../../dllcrt2.o:(.text+0x60): first defined here collect2.exe: error: ld returned 1 exit status

Thanks for help.

Ballarat

Answer 1

You need to link with the -nostdlib option like so:

gcc -nostdlib -shared -Wl,-soname,libglew32.dll -Wl,--out-implib,lib/libglew32.dll.a    -o lib/glew32.dll src/glew.o -L/mingw/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lkernel32

Glew defines DllMainCRTStartup which is also defined in the CRT. Hence your problem.

Tula

If this is true, little doubt it is given the linker error, this is beyond incredibly nasty. -nostdlib is certainly not a valid workaround, very important to get the CRT initialized properly in a DLL. Proper advice should surely be to only ever use Glew in an EXE project. That's what it is was made for, a simple way to get started on OpenGL. – Somniloquy

I've had this problem while following github.com/KhronosGroup/OpenCL-Guide/blob/main/chapters/… - -nostdlib stopped that link error, but then it couldn't find memset. I think it needs the DllMainCRTStartup disabling. – Atom