MinGW compilation "file not recognized: File format not recognized"

Question

I'm trying to compile a c++ program and I am having some issues. In particular, when I use x86_64-w64-mingw32-gcc as my compiler, it complains half way through my compilation saying "tmp/src/libfastms/solver/solver.cpp.o: file not recognized: File format not recognized".

Here is my makefile (not mine, I'm trying to adapt this makefile to a cygwin environment) https://pastebin.com/vgnVYJUL

Here is the console output when I run make:

x86_64-w64-mingw32-gcc -c -o tmp/src/libfastms/solver/solver.cpp.o src/libfastms/solver/solver.cpp  -Wall -O3 -m64  -Isrc/libfastms  -DDISABLE_OPENMP -DDISABLE_OPENCV -DDISABLE_CUDA
x86_64-w64-mingw32-gcc -c -o tmp/src/libfastms/solver/solver_base.cpp.o src/libfastms/solver/solver_base.cpp  -Wall -O3 -m64  -Isrc/libfastms  -DDISABLE_OPENMP -DDISABLE_OPENCV -DDISABLE_CUDA
x86_64-w64-mingw32-gcc -c -o tmp/src/libfastms/solver/solver_host.cpp.o src/libfastms/solver/solver_host.cpp  -Wall -O3 -m64  -Isrc/libfastms  -DDISABLE_OPENMP -DDISABLE_OPENCV -DDISABLE_CUDA
x86_64-w64-mingw32-gcc -c -o tmp/src/libfastms/util/has_cuda.cpp.o src/libfastms/util/has_cuda.cpp  -Wall -O3 -m64  -Isrc/libfastms  -DDISABLE_OPENMP -DDISABLE_OPENCV -DDISABLE_CUDA
x86_64-w64-mingw32-gcc -c -o tmp/src/libfastms/util/image_mat.cpp.o src/libfastms/util/image_mat.cpp  -Wall -O3 -m64  -Isrc/libfastms  -DDISABLE_OPENMP -DDISABLE_OPENCV -DDISABLE_CUDA
ld -r -o tmp/src/libfastms/libfastms.o tmp/src/libfastms/solver/solver.cpp.o tmp/src/libfastms/solver/solver_base.cpp.o tmp/src/libfastms/solver/solver_host.cpp.o tmp/src/libfastms/util/has_cuda.cpp.o tmp/src/libfastms/util/image_mat.cpp.o
tmp/src/libfastms/solver/solver.cpp.o: file not recognized: File format not recognized
Makefile:167: recipe for target 'tmp/src/libfastms/libfastms.o' failed
make: *** [tmp/src/libfastms/libfastms.o] Error 1

Some other notes:

• I don't have this problem when I compile with g++ (only seems to be minGW)
• A common solution to this problem is to clean the directory of residual object files. This does not work.
• Another common reason for this is trying to compile .h files. Obviously I am not doing this.

Thanks in advance.

Solution

You are compiling your object files with a 64-bit compiler driver, w64-mingw32-gcc, and with -m64 you are explicitly directing it to generate 64-bit code (unnecessarily, as that is its default). But you are linking with a 32-bit linker that does not understand 64-bit object files.

This is happening because in your makefile you are, unusually, invoking ld explicitly for your incremental solver linkage:

COMMAND_LINK_SOLVER=ld -r -o $@ $^

rather than delegating linkage to your compiler driver in the usual way, and a 32-bit ld from a different toolchain is being found in your PATH before the 64-bit one belonging to your mingw-w64 toolchain.

To avoid this, invoke the linker via the compiler driver as normal, which for your solver linkage means:

COMMAND_LINK_SOLVER=$(GXX) -Wl,-r -o $@ $^

You can depend on w64-mingw32-gcc to invoke the ld that was installed with it.

There is no need to correct your main linkage as it is already done the right way.