Are llvm-gcc and clang binary compatible with gcc? - particularly mingw gcc on Windows
If I build a static library with llvm-gcc, then link it with a program compiled using mingw gcc, will the result work?
The same for other combinations of llvm-gcc, clang and normal gcc. I'm interested in how this works out on Linux (using normal non-mingw gcc, of course) and other platforms as well, but the emphasis is on Windows.
I'm also interested in all languages, but with a strong emphasis on C and C++ - obviously clang doesn't support Fortran etc, but I believe llvm-gcc does.
I assume they all use the ELF file format, but what about call conventions, virtual table layouts etc?
Answer
Yes, for C code Clang and GCC are compatible (they both use the GNU Toolchain for linking, in fact.) You just have to make sure that you tell clang to create compiled objects and not intermediate bitcode objects. C ABI is well-defined, so the only issue is storage format.
C++ is not portable between compilers in the slightest; different compilers use different virtual table calls, constructors, destruction, name mangling, template implementations, etc. As a rule you should assume objects from one C++ compiler will not work with another.
However yes, at the time of writing Clang++ is able to use GCC/C++ compiled libraries as well; I recently set up a rig to compile C++ programs with clang using G++'s standard runtime library and it compiles+links just fine.