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, 9 insertions, 0 deletions

diff --git a/src/buildtool/main/main.cpp b/src/buildtool/main/main.cpp
index 81a932a1..79c7c0cb 100644
--- a/src/buildtool/main/main.cpp
+++ b/src/buildtool/main/main.cpp
@@ -1264,7 +1264,16 @@ auto main(int argc, char* argv[]) -> int {
             Evaluator::SetExpressionLogLimit(
                 *arguments.analysis.expression_log_limit);
         }
+
 #ifndef BOOTSTRAP_BUILD_TOOL
+        /**
+         * The current implementation of libgit2 uses pthread_key_t incorrectly
+         * on POSIX systems to handle thread-specific data, which requires us to
+         * explicitly make sure the main thread is the first one to call
+         * git_libgit2_init. Future versions of libgit2 will hopefully fix this.
+         */
+        GitContext::Create();
+
         SetupHashFunction();
         SetupExecutionConfig(
             arguments.endpoint, arguments.build, arguments.rebuild);