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, 7 insertions, 1 deletions

diff --git a/src/buildtool/file_system/git_context.cpp b/src/buildtool/file_system/git_context.cpp
index 04d4498d..084e9d58 100644
--- a/src/buildtool/file_system/git_context.cpp
+++ b/src/buildtool/file_system/git_context.cpp
@@ -15,6 +15,7 @@
 #include "src/buildtool/file_system/git_context.hpp"
 
 #include "src/buildtool/logging/logger.hpp"
+#include "src/utils/cpp/gsl.hpp"
 
 extern "C" {
 #include <git2.h>
@@ -34,4 +35,9 @@ GitContext::~GitContext() noexcept {
         git_libgit2_shutdown();
     }
 #endif
-}
\ No newline at end of file
+}
+
+void GitContext::Create() noexcept {
+    static GitContext git_state{};
+    Expects(git_state.initialized_);
+}