[PATCH] [compiler-rt] Fix/workaround for OS X truncated stacktraces taken by external tools

[Kuba Brecka]

This patch is a proposed solution for https://code.google.com/p/address-sanitizer/issues/detail?id=375:

When the stacktraces are captured and printed by ASan itself, they are fine, but when the program has already printed the report (or is just printing it), capturing a stacktrace via other means is broken. "Other means" include OS X CrashReporter, debuggers or calling backtrace() within the program. For example calling backtrace() from a sanitizer_set_death_callback function prints a very truncated stacktrace:

    0   crashlog-stacktraces.c.tmp          0x000000010fb1c397 death_function + 471
    1   libclang_rt.asan_osx_dynamic.dylib  0x000000010fb72c1f _ZN11__sanitizer3DieEv + 15

The same can happen even within lldb (I'm seeing this for 32-bit x86):

    (lldb) bt
    * thread #1: tid = 0x9ec2d, 0x0000209a crashlog-stacktraces.c.tmp`death_function + 42 at crashlog-stacktraces.c:10, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
      * frame #0: 0x0000209a crashlog-stacktraces.c.tmp`death_function + 42 at crashlog-stacktraces.c:10
        frame #1: 0x0005eaf6 libclang_rt.asan_osx_dynamic.dylib`__sanitizer::Die() + 22
        frame #2: 0x00058136 libclang_rt.asan_osx_dynamic.dylib`__asan::ScopedInErrorReport::~ScopedInErrorReport() + 102
        frame #3: 0x00057fcf libclang_rt.asan_osx_dynamic.dylib`__asan::ScopedInErrorReport::~ScopedInErrorReport() + 15
        frame #4: 0x00057acc libclang_rt.asan_osx_dynamic.dylib`__asan_report_error + 4204
    (lldb) 

This patch forces __asan_report_error to always have a stack frame by using the ENABLE_FRAME_POINTER macro, which we are already using elsewhere (asan_mac.cc).

http://reviews.llvm.org/D7103

Files:
  lib/asan/asan_mac.cc
  lib/asan/asan_report.cc
  lib/sanitizer_common/sanitizer_internal_defs.h

Index: lib/asan/asan_mac.cc
===================================================================
--- lib/asan/asan_mac.cc
+++ lib/asan/asan_mac.cc
@@ -374,13 +374,6 @@
     work(); \
   }
 
-// Forces the compiler to generate a frame pointer in the function.
-#define ENABLE_FRAME_POINTER                                       \
-  do {                                                             \
-    volatile uptr enable_fp;                                       \
-    enable_fp = GET_CURRENT_FRAME();                               \
-  } while (0)
-
 INTERCEPTOR(void, dispatch_async,
             dispatch_queue_t dq, void(^work)(void)) {
   ENABLE_FRAME_POINTER;
Index: lib/asan/asan_report.cc
===================================================================
--- lib/asan/asan_report.cc
+++ lib/asan/asan_report.cc
@@ -937,6 +937,8 @@
 
 void __asan_report_error(uptr pc, uptr bp, uptr sp, uptr addr, int is_write,
                          uptr access_size) {
+  ENABLE_FRAME_POINTER;
+  
   // Determine the error type.
   const char *bug_descr = "unknown-crash";
   if (AddrIsInMem(addr)) {
Index: lib/sanitizer_common/sanitizer_internal_defs.h
===================================================================
--- lib/sanitizer_common/sanitizer_internal_defs.h
+++ lib/sanitizer_common/sanitizer_internal_defs.h
@@ -325,4 +325,11 @@
     } while (internal_iserror(res, &rverrno) && rverrno == EINTR); \
   }
 
+// Forces the compiler to generate a frame pointer in the function.
+#define ENABLE_FRAME_POINTER                                       \
+  do {                                                             \
+    volatile uptr enable_fp;                                       \
+    enable_fp = GET_CURRENT_FRAME();                               \
+  } while (0)
+
 #endif  // SANITIZER_DEFS_H

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