memcheck: fix race in libgit2...

...caused by incorrectly setting and resetting the library internal
state and the misuse of pthreads in libgit2.

Normally, git_libgit2_init and git_libgit2_shutdown should span the
life of a worker thread in order to be safely used. However, due to
an incorrect implementation of libgit2's threadstate with pthreads,
on unix systems there is a race condition.

Until the use of pthread_key_t is corrected in libgit2, we need to
apply a workaround by always ensuring that the main thread is the
first thread reaching the GitContext constructor.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/buildtool/file_system/git_repo.cpp b/src/buildtool/file_system/git_repo.cpp
index d135875a..9fe63fb6 100644
--- a/src/buildtool/file_system/git_repo.cpp
+++ b/src/buildtool/file_system/git_repo.cpp
@@ -391,7 +391,7 @@ auto GitRepo::InitAndOpen(std::filesystem::path const& repo_path,
         static std::mutex repo_mutex{};
         std::unique_lock lock{repo_mutex};
 
-        auto git_state = GitContext();  // initialize libgit2
+        GitContext::Create();  // initialize libgit2
 
         // check if init is actually needed
         if (git_repository_open_ext(nullptr,
@@ -1015,7 +1015,7 @@ auto GitRepo::GetRepoRootFromPath(std::filesystem::path const& fpath,
     return std::nullopt;
 #else
     try {
-        auto git_state = GitContext();  // initialize libgit2
+        GitContext::Create();  // initialize libgit2
 
         git_buf buffer = GIT_BUF_INIT_CONST(NULL, 0);
         auto res = git_repository_discover(&buffer, fpath.c_str(), 0, nullptr);