create MSVC import library with MinGW tools

Question

We are currently switching the W32 build-process of a cross-platform (linux, osx, w32) project from VisualStudio to mingw.

One of the problems we are facing is, that our projects creates a dynamic library (foo.dll), against which 3rd party projects can link. For this to work on W32/MSVC, an import library is required (foo.lib).

Now, following the documentation it is pretty easy to create a .def file which holds all the information required for importing the library:

 gcc -shared -o foo.dll foo-*.o -Wl,--output-def,foo.def

In order to use the foo.def file, the docs tell me to use the Microsoft LIB tool to build a foo.lib from it:

 lib /machine:i386 /def:testdll.def

This obviously requires me to have (a subset of) MSVC installed on the build computer. However, we'd like to cross-compile the entire thing on our linux systems (probably even on some CI), which makes the installation of MSVC rather tedious.

So I wonder, whether there's a native MinGW way to convert the foo.def file into a foo.lib import library?

(We are aware that in the end, only MSVC users will require the import library and that they will have the lib tool ready at hand. However, since we've always shipped the foo.lib file, switching to foo.def would break 3rd parties build systems - something we would like to avoid).

Answer 1

we'd like to cross-compile the entire thing on our linux systems

I'm not aware of any MS LIB clone portable to Linux, however POLIB from Pelles C distribution is free, small, self-contained and compatible with MS tool. It has no dependencies other than kernel32.dll, so, I believe, it will run under Wine too.

Answer 2

To produce an import library that is similar to the one generated by Microsoft's link.exe, you can use llvm-dlltool (part of the LLVM compiler project):

llvm-dlltool -m i386:x86-64 -d foo.def -l foo.lib

Substitute i386:x86-64 for i386 if you would like to create a 32-bit library. For more details see this answer to How to generate an import library (LIB-file) from a DLL?.

Note that some MinGW projects generate a .dll.a file (as produced by binutils dlltool). While this could be renamed to .lib and function as import library, I found that it would result in broken binaries if a MSVC projects links to multiple .dll.a libraries. So stick to llvm-dlltool instead for improved compatibility.