From c19e37e1764ce3e77c474370484e525fbc87e12b Mon Sep 17 00:00:00 2001 From: Reid Kleckner Date: Thu, 5 Jun 2014 00:13:43 +0000 Subject: [PATCH] Flush C stdio streams upon process termination Due to what can only be described as a CRT bug, stdout and amazingly even stderr are not always flushed upon process termination, especially when the system is under high threading pressure. I have found two repros for this: 1) In lib\Support\Threading.cpp, change sys::Mutex to an std::recursive_mutex and run check-clang. Usually between 30 and 40 tests will fail. 2) Add OutputDebugStrings in code that runs during static initialization and static shutdown. This will sometimes generate similar failures. After a substantial amount of troubleshooting and debugging, I found that I could reproduce this from the command line without running check-clang. Simply make the mutex change described in #1, then manually run the following command many times by running it once, then pressing Up -> Enter very quickly: D:\src\llvm\build\vs2013\Debug\bin\c-index-test.EXE -cursor-at=D:\src\llvm\tools\clang\test\Index\targeted-preamble.h:2:15 D:\src\llvm\tools\clang\test\Index\targeted-cursor.c -include D:\src\llvm\build\vs2013\tools\clang\test\Index\Output\targeted-cursor.c.tmp.h -Xclang -error-on-deserialized-decl=NestedVar1 -Xclang -error-on-deserialized-decl=TopVar | D:\src\llvm\build\vs2013\Debug\bin\FileCheck.EXE D:\src\llvm\tools\clang\test\Index\targeted-cursor.c -check-prefix=PREAMBLE-CURSOR1 Sporadically they will fail, and attaching a debugger to a failed instance indicates that stdin of FileCheck.exe is empty. Note that due to the repro in #2, we can rule out a bug in the STL's mutex implementation, and instead conclude that this is a real flake in the windows test harness. Test Plan: Without patch: Ran check-clang 10 times and saw over 30 Unexpected failures on every run. With patch: Ran check-clang 10 times and saw 0 unexpected failures across all runs. Reviewers: rnk Differential Revision: http://reviews.llvm.org/D4021 Patch by Zachary Turner! git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210225 91177308-0d34-0410-b5e6-96231b3b80d8 --- tools/c-arcmt-test/c-arcmt-test.c | 12 +++++++++--- tools/c-index-test/c-index-test.c | 12 +++++++++--- 2 files changed, 18 insertions(+), 6 deletions(-) diff --git a/tools/c-arcmt-test/c-arcmt-test.c b/tools/c-arcmt-test/c-arcmt-test.c index 56a4132dba..60faed03dc 100644 --- a/tools/c-arcmt-test/c-arcmt-test.c +++ b/tools/c-arcmt-test/c-arcmt-test.c @@ -97,14 +97,20 @@ typedef struct thread_info { void thread_runner(void *client_data_v) { thread_info *client_data = client_data_v; client_data->result = carcmttest_main(client_data->argc, client_data->argv); -#ifdef __CYGWIN__ - fflush(stdout); /* stdout is not flushed on Cygwin. */ -#endif +} + +static void flush_atexit(void) { + // stdout, and surprisingly even stderr, are not always flushed on process + // and thread exit, particularly when the system is under heavy load. + fflush(stdout); + fflush(stderr); } int main(int argc, const char **argv) { thread_info client_data; + atexit(flush_atexit); + #if defined(_WIN32) if (getenv("LIBCLANG_LOGGING") == NULL) putenv("LIBCLANG_LOGGING=1"); diff --git a/tools/c-index-test/c-index-test.c b/tools/c-index-test/c-index-test.c index 1d5cb1434c..576f3c4a58 100644 --- a/tools/c-index-test/c-index-test.c +++ b/tools/c-index-test/c-index-test.c @@ -4116,14 +4116,20 @@ typedef struct thread_info { void thread_runner(void *client_data_v) { thread_info *client_data = client_data_v; client_data->result = cindextest_main(client_data->argc, client_data->argv); -#ifdef __CYGWIN__ - fflush(stdout); /* stdout is not flushed on Cygwin. */ -#endif +} + +static void flush_atexit(void) { + // stdout, and surprisingly even stderr, are not always flushed on process + // and thread exit, particularly when the system is under heavy load. + fflush(stdout); + fflush(stderr); } int main(int argc, const char **argv) { thread_info client_data; + atexit(flush_atexit); + #ifdef CLANG_HAVE_LIBXML LIBXML_TEST_VERSION #endif -- 2.40.0