From 4656bd0a6a26e3e60707406cac920c74d45b90de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Max=20Neunh=C3=B6ffer?= <max@arangodb.com>
Date: Fri, 13 Sep 2019 12:27:30 +0200
Subject: [PATCH] Fix a shutdown busy loop after main if two exceptions
 collide. (#9982)

---
 arangod/RestServer/arangod.cpp |  5 +++++
 lib/Basics/files.cpp           | 18 ++++++++++++++++++
 lib/Basics/operating-system.h  |  9 +++++++++
 3 files changed, 32 insertions(+)

diff --git a/arangod/RestServer/arangod.cpp b/arangod/RestServer/arangod.cpp
index 7a1c6e5756..d59a48bd3b 100644
--- a/arangod/RestServer/arangod.cpp
+++ b/arangod/RestServer/arangod.cpp
@@ -330,6 +330,11 @@ namespace arangodb {
 // arangodb::application_features::ApplicationServer::server->beginShutdown();
 
 int main(int argc, char* argv[]) {
+#ifdef __linux__
+  // Do not delete this! See lib/Basics/operating-system.h for details.
+  ThrowSomeException();
+#endif
+
   std::string workdir(arangodb::basics::FileUtils::currentDirectory().result());
 #ifdef __linux__
 #if USE_ENTERPRISE
diff --git a/lib/Basics/files.cpp b/lib/Basics/files.cpp
index 1e1863571c..8ededb704c 100644
--- a/lib/Basics/files.cpp
+++ b/lib/Basics/files.cpp
@@ -2642,3 +2642,21 @@ bool TRI_GETENV(char const* which, std::string& value) {
   return true;
 #endif
 }
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief bug fix for some race on libmusl and static linking
+//////////////////////////////////////////////////////////////////////////////
+
+// The following function just throws an exception and catches it. This is
+// used on Linux for the case that we link statically and the underlying
+// C-library is libmusl. This configuration has a bug in libgcc which
+// triggers a shutdown busy loop (after main), provided the very first
+// exception being thrown in the life of the process happens in two threads
+// at the same time. By throwing right at the beginning of main() when the
+// process is still single-threaded, we circumvent this problem.
+#ifdef __linux__
+void ThrowSomeException() {
+  try { throw 42; } catch(int const&) {};
+}
+#endif
+
diff --git a/lib/Basics/operating-system.h b/lib/Basics/operating-system.h
index 57a9b3631a..46b4efd306 100644
--- a/lib/Basics/operating-system.h
+++ b/lib/Basics/operating-system.h
@@ -671,6 +671,15 @@
 #define TRI_uid_t uid_t
 #define TRI_gid_t gid_t
 
+// The following function just throws an exception and catches it. This is
+// used on Linux for the case that we link statically and the underlying
+// C-library is libmusl. This configuration has a bug in libgcc which
+// triggers a shutdown busy loop (after main), provided the very first
+// exception being thrown in the life of the process happens in two threads
+// at the same time. By throwing right at the beginning of main() when the
+// process is still single-threaded, we circumvent this problem.
+void ThrowSomeException();
+
 #endif
 
 // -----------------------------------------------------------------------------