[compiler-rt] r266869 - Always inlining PrintCurrentStackSlow of tsan library to fix tail-call issue

[Chuang-Yu Cheng via llvm-commits]

Author: cycheng
Date: Wed Apr 20 05:28:41 2016
New Revision: 266869

URL: http://llvm.org/viewvc/llvm-project?rev=266869&view=rev
Log:
Always inlining PrintCurrentStackSlow of tsan library to fix tail-call issue

The real problem is that sanitizer_print_stack_trace obtains current PC and
expects the PC to be in the stack trace after function calls. We don't
prevent tail calls in sanitizer runtimes, so this assumption does not
necessary hold.

We add "always inline" attribute on PrintCurrentStackSlow to address this
issue, however this solution is not reliable enough, but unfortunately, we
don't see any simple, reliable solution.

Reviewers: samsonov hfinkel kbarton tjablin dvyukov kcc

http://reviews.llvm.org/D19148

Thanks Hal, dvyukov, and kcc for invaluable discussion, I have even borrowed
part of dvyukov's summary as my commit message!

Modified:
    compiler-rt/trunk/lib/tsan/rtl/tsan_rtl_report.cc

Modified: compiler-rt/trunk/lib/tsan/rtl/tsan_rtl_report.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/tsan/rtl/tsan_rtl_report.cc?rev=266869&r1=266868&r2=266869&view=diff
==============================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_rtl_report.cc (original)
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_rtl_report.cc Wed Apr 20 05:28:41 2016
@@ -680,6 +680,14 @@ void PrintCurrentStack(ThreadState *thr,
   PrintStack(SymbolizeStack(trace));
 }
 
+// Always inlining PrintCurrentStackSlow, because LocatePcInTrace assumes
+// __sanitizer_print_stack_trace exists in the actual unwinded stack, but
+// tail-call to PrintCurrentStackSlow breaks this assumption because
+// __sanitizer_print_stack_trace disappears after tail-call.
+// However, this solution is not reliable enough, please see dvyukov's comment
+// http://reviews.llvm.org/D19148#406208
+// Also see PR27280 comment 2 and 3 for breaking examples and analysis.
+ALWAYS_INLINE
 void PrintCurrentStackSlow(uptr pc) {
 #ifndef SANITIZER_GO
   BufferedStackTrace *ptrace =