Convert from MinGW .a to VC++ .lib
I have an old library (in C++) that I'm only able to build on MinGW+MSYS32 on Windows. From that I can produce a .a static library file generated from GNU libtool. My primary development is done in Visual Studio 2008. If I try to take the MinGW produced library and link it in Visual Studio, it complains about missing externals. This is most likely due to the C++ symbol mangling that is done, and that it doesn't match whats in the .a file. Is there any know way to convert a static .a file to VC++ library format?
Answer
If symbols are mangled differently, the compilers are using a different ABI and you won't be able to "convert" or whatever the compiled libraries: the reason names are mangled in different ways is intentional to avoid users from ever succeeding with building an executable from object files using different ABIs. The ABI defines how arguments are passed, how virtual function tables are represented, how exceptions are thrown, the size of basic data types, and quite a number of other things. The name mangling is also part of this and carefully chosen to be efficient and different from other ABIs on the same platform. The easiest way to see if the name mangling is indeed different is to compiler a file with a couple of functions using only basic types with both compilers and have a look at the symbols (on UNIX I would use nm for this; I'm not a Windows programmer and thus I don't know what tool to use there).
Based on Wikipedia it seems that MinGW also uses a different run-time library: the layout and the implementation of the standard C++ library used by MinGW (libstdc++) and Visual Studio (Dinkumware) is not compatible. Even if the ABI between the two compilers is the same, the standard C++ library used isn't. If the ABI is the same you would need to replace set things up so that one compiler uses the standard library of the respective other compiler. There is no way to do this with the already compiled library. I don't know if this is doable.
Personally I wouldn't bother with trying to link things between these two different compiler because it is bound not to work at all. Instead, you'd need to port the implementation to a common compiler and go from there.