Workaround ARM tracing issues for non-component builds.

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 "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 #if defined(OS_WIN)
 struct _EXCEPTION_POINTERS;
 struct _CONTEXT;
 #endif
 
 #if defined(OS_POSIX) && ( \
     defined(__i386__) || defined(__x86_64__) || \
-    (defined(__arm__) && !defined(__thumb__)))
+    (defined(__arm__) && ( \
+        /* We don't normally support thumb mode... */ \
+        !defined(__thumb__) || \
+        /* ...unless we're building non-component build with Clang. \
+           Clang properly sets up fp register, so we can walk stack frames, \
+           but it pushes arbitrary number of registers between fp (r7) and \
+           lr (r14). However in non-component build, where all code is \
+           inside a single mapped region, it's possible to guess lr by \
+           probing up to 7 locations on the stack. */ \
+        (defined(__clang__) && !defined(COMPONENT_BUILD) && \
+            defined(OS_ANDROID)))))
 #define HAVE_TRACE_STACK_FRAME_POINTERS 1
 #else
 #define HAVE_TRACE_STACK_FRAME_POINTERS 0
 #endif
 
 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
@@ skipping 92 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_