Explicitly specify whether to emit frame pointers by default.

base/debug/stack_trace.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_DEBUG_STACK_TRACE_H_
 #define BASE_DEBUG_STACK_TRACE_H_
 
 #include <stddef.h>
 
 #include <iosfwd>
 #include <string>
 
 #include "base/base_export.h"
 #include "base/debug/debugging_flags.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 #if defined(OS_WIN)
 struct _EXCEPTION_POINTERS;
 struct _CONTEXT;
 #endif
 
-// Fast stack trace capture using frame pointers is only available under POSIX
-// platforms, and only for certain architectures, and only when frame pointers
-// are enabled in the build.
-#if defined(OS_POSIX)
-#if BUILDFLAG(ENABLE_PROFILING) || !defined(NDEBUG)
-
-#if defined(__i386__) || defined(__x86_64__)
-#define HAVE_TRACE_STACK_FRAME_POINTERS 1
-#elif defined(__arm__) && !defined(__thumb__)
-#define HAVE_TRACE_STACK_FRAME_POINTERS 1
-#else  //  defined(__arm__) && !defined(__thumb__)

[Primiano Tucci (use gerrit), 2017/03/30 13:15:03]

where did this logic go?
The deal here is that we can use frame pointers only when building in ARM (i.e.
non-thumb mode), which happens IIRC with profiling=1.
Makes sense to move this to build-time, but at very least I'd expect something
conditioned by arm_use_thumb or similar, which I don't see here.

[erikchen, 2017/03/30 22:12:47]

The !thumb logic was added here:
https://bugs.chromium.org/p/chromium/issues/detail?id=602701#c5

Either:
1) We can't emit frame_pointers on thumb. I would hope that clang throws an
error when we try to force frame pointers anyways. In this case, we should
update the logic in compiler.gni to accurately reflect this.

2) For some reason, stack walking with frame pointers doesn't work on thumb. In
this case, we should update the stack-walking logic /conditionals to indicate
this. It has nothing to do with whether stacks have frame pointers.

3) Everything works fine on thumb, and this CL doesn't need to change.

-#define HAVE_TRACE_STACK_FRAME_POINTERS 0
-#endif  //  defined(__arm__) && !defined(__thumb__)
-
-#else  //  BUILDFLAG(ENABLE_PROFILING) || !defined(NDEBUG)
-#define HAVE_TRACE_STACK_FRAME_POINTERS 0
-#endif  //  BUILDFLAG(ENABLE_PROFILING) || !defined(NDEBUG)
-
-#else  // defined(OS_POSIX)
-#define HAVE_TRACE_STACK_FRAME_POINTERS 0
-#endif  // defined(OS_POSIX)
-
 namespace base {
 namespace debug {
 
 // Enables stack dump to console output on exception and signals.
 // When enabled, the process will quit immediately. This is meant to be used in
 // unit_tests only! This is not thread-safe: only call from main thread.
 // In sandboxed processes, this has to be called before the sandbox is turned
 // on.
 // Calling this function on Linux opens /proc/self/maps and caches its
 // contents. In non-official builds, this function also opens the object files
@@ skipping 145 matching lines @@
                          int base,
                          size_t padding);
 #endif  // defined(OS_POSIX) && !defined(OS_ANDROID)
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_STACK_TRACE_H_