How to use libgit2 from a native C++ application on Windows? (Microsoft VC++)

Question

Summary: Is there any tiny example on how to build the Win32 C++ console application that uses the libgit2 library (sources available at GitHub)?

I have followed the readme and the wiki on how to build the library on Windows using the CMake, and it worked smoothly (only a single unit-test error).

Now, I want to build a simple console application that uses the library -- using Microsoft Visual Studio C++ 2010 (the.vcxproj and the.sln). I have found the general.c code in the libgit2 examples, and I would like to do the same from my C++ application. No success -- I feel really stupid today...

I have noticed there is libqgit2 for C++ and Qt. Is there anything similar for pure C++? Or is there a way to use the C library from C++ application?

Update: I have renamed the general.c to general.cpp, added the libgit2 include path to the project and the path to the .lib files, changed the #include <stdio.h> to #include <cstdio>, and compiled. The following link errors appear:

1>------ Build started: Project: libgit2_general, Configuration: Debug Win32 ------
1>general.obj : error LNK2019: unresolved external symbol _git_repository_free referenced in function _main
1>general.obj : error LNK2019: unresolved external symbol _git_config_get_string referenced in function _main
1>general.obj : error LNK2019: unresolved external symbol _git_config_get_int32 referenced in function _main
1>general.obj : error LNK2019: unresolved external symbol _git_config_open_ondisk referenced in function _main
1>general.obj : error LNK2019: unresolved external symbol _git_strarray_free referenced in function _main
... etc.
1>general.obj : error LNK2019: unresolved external symbol _git_repository_open referenced in function _main
1>general.obj : error LNK2019: unresolved external symbol _giterr_last referenced in function "void __cdecl check_error(int,char const *)" (?check_error@@YAXHPBD@Z)
1>D:\Tutorial\libgit2_general\Debug\libgit2_general.exe : fatal error LNK1120: 56 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

This strongly suggests a calling convention mismatch to me. libgit2 uses __stdcall by default, for a number of reasons, while Visual Studio defaults to creating projects that use the __cdecl calling convention. While your program can use either calling convention and successfully call libgit2 using a different one, the easiest solution is probably just to use the same calling convention for both.

When you configure libgit2, you can turn off the STDCALL flag, which will cause it to emit a library built with __cdecl calling conventions:

cmake %PATH_TO_LIBGIT2_SOURCE% -DTHREADSAFE=ON -DSTDCALL=OFF
cmake --build .

Answer 2

It's a little surprising if you generated the project from CMake, bit it could be that you're not linking to libgit2.lib. Make sure you have git2.dll in Project Properties -> Configuration Properties -> Linker -> Input -> Additional Dependencies.