Turn symbolication on for ASan unit test.

[alekseyshl]

Summary

On PowerPC and ARM (possibly, need to verify), couple tests involving
pthread_exit fail due to leaks detected by LSan. pthread_exit tries
to perform unwinding that leads to dlopen'ing libgcc_s.so. dlopen
mallocs "libgcc_s.so" string which confuses LSan, it fails to
realize that this allocation happens in dynamic linker and should
be ignored.
Symbolized leak report is required to define a suppression for this
known problem.

[eugenis]

LGTM
good catch
do you know how big is this slowdown the comment talks about?

[kubamracek]

Can we fix this in a different way? The slowdown on Mac is huge, especially when not running with llvm-symbolizer but with atos.

[kubamracek]

On PowerPC and ARM

If this problem only exists on PowerPC and ARM, can you perhaps keep symbolize=false on macOS?

[alekseyshl]

Sure, let me experiment a bit on x86 and we definitely can keep Mac without symbolization.

[alekseyshl]

For the context, here's the test I used:

#include <pthread.h>
static void *PthreadExit(void *a) {
  pthread_exit(0);
  return 0;
}
int main(int argc, char** argv) {
  pthread_t t;
  pthread_create(&t, 0, PthreadExit, 0);
  pthread_join(t, 0);
  return 0;
}

and here's the stack LSan reports on my ppc machine:

Direct leak of 56 byte(s) in 1 object(s) allocated from:

#0 0x101154dc in malloc */llvm/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:66:3
#1 0x3fffb3dddf00 in _dl_map_object_deps (*/lib64/ld64.so.2+0x1df00)
#2 0x3fffb3de7b74 in dl_open_worker (*/lib64/ld64.so.2+0x27b74)
#3 0x3fffb3de07f4 in _dl_catch_error (*/lib64/ld64.so.2+0x207f4)
#4 0x3fffb3de7094 in _dl_open (*/lib64/ld64.so.2+0x27094)
#5 0x3fffb220de94 in do_dlopen (*/lib64/libc.so.6+0x17de94)
#6 0x3fffb3de07f4 in _dl_catch_error (*/lib64/ld64.so.2+0x207f4)
#7 0x3fffb220e00c in __GI___libc_dlopen_mode (*/lib64/libc.so.6+0x17e00c)
#8 0x3fffb2375a8c in pthread_cancel_init (*/lib64/libpthread.so.0+0x15a8c)
#9 0x3fffb2375d8c in _Unwind_ForcedUnwind (*/lib64/libpthread.so.0+0x15d8c)
#10 0x3fffb23729bc in __GI___pthread_unwind (*/lib64/libpthread.so.0+0x129bc)
#11 0x3fffb23693e0 in __pthread_exit (*/lib64/libpthread.so.0+0x93e0)
#12 0x10132448 in PthreadExit(void*) */leak_test.cc:4:3
#13 0x10123a70 in __asan::AsanThread::ThreadStart(unsigned long, __sanitizer::atomic_uintptr_t*) */llvm/llvm/projects/compiler-rt/lib/asan/asan_thread.cc:257:25
#14 0x100fa4b8 in asan_thread_start(void*) */llvm/llvm/projects/compiler-rt/lib/asan/asan_interceptors.cc:298:13
#15 0x3fffb2367da8 in start_thread (*/lib64/libpthread.so.0+0x7da8)
#16 0x3fffb20be668 in __clone (*/lib64/libc.so.6+0x2e668)

The similar env and test on x86 does not report any leaks.

[alekseyshl]

• Turn symbolization on for PPC and Thumb only to do not slow down other platforms.

lib/asan/tests/asan_test_main.cc

 //===-- asan_test_main.cc -------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of AddressSanitizer, an address sanity checker.
 //
 //===----------------------------------------------------------------------===//
 #include "asan_test_utils.h"
 #include "sanitizer_common/sanitizer_platform.h"
 
-// Default ASAN_OPTIONS for the unit tests. Let's turn symbolication off to
-// speed up testing (unit tests don't use it anyway).
+// Default ASAN_OPTIONS for the unit tests.
 extern "C" const char* __asan_default_options() {
 #if SANITIZER_MAC
   // On Darwin, we default to `abort_on_error=1`, which would make tests run
-  // much slower. Let's override this and run lit tests with 'abort_on_error=0'.
-  // Also, make sure we do not overwhelm the syslog while testing.
+  // much slower. Let's override this and run lit tests with 'abort_on_error=0'
+  // and make sure we do not overwhelm the syslog while testing. Also, let's
+  // turn symbolization off to speed up testing, especially when not running
+  // with llvm-symbolizer but with atos.
   return "symbolize=false:abort_on_error=0:log_to_syslog=0";
+#elif SANITIZER_PPC || defined(__thumb__)
+  // On PowerPC and ARM Thumb, a couple tests involving pthread_exit fail due to
+  // leaks detected by LSan. pthread_exit tries to perform unwinding that leads
+  // to dlopen'ing libgcc_s.so. dlopen mallocs "libgcc_s.so" string which
+  // confuses LSan, it fails to realize that this allocation happens in dynamic
+  // linker and should be ignored.  Symbolized leak report is required to define
+  // a suppression for this known problem.
+  return "";
 #else
+  // Let's turn symbolization off to speed up testing (more than 3 times speedup
+  // observed).
   return "symbolize=false";
 #endif
 }
 
 namespace __sanitizer {
 bool ReexecDisabled() {
 #if __has_feature(address_sanitizer) && SANITIZER_MAC
   // Allow re-exec in instrumented unit tests on Darwin.  Technically, we only