Enable frame pointers explicitly under ARM32.

build/config/compiler/compiler.gni

 # Copyright 2015 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/pgo/pgo.gni")
 import("//build/config/sanitizers/sanitizers.gni")
@@ skipping 48 matching lines @@
   # Note that doing a link repro uses a lot of disk space and slows down the
   # build, so this shouldn't be enabled on too many targets.
   #
   # See crbug.com/669854.
   linkrepro_root_dir = ""
 
   # Whether or not we should use position independent code.
   use_pic = true
 }
 
-# Whether to emit frame pointers by default.
+# Determine the default setting for enable_frame_pointers, based on the platform
+# and build arguments.
 if (is_mac || is_ios) {
-  enabled_frame_pointers = true
+  _default_enable_frame_pointers = true
 } else if (is_win) {
   # 64-bit Windows ABI doesn't support frame pointers.
   if (target_cpu == "x64") {
-    enabled_frame_pointers = false
+    _default_enable_frame_pointers = false
   } else {
-    enabled_frame_pointers = true
+    _default_enable_frame_pointers = true
   }
+} else if (current_cpu == "arm64") {
+  # Ensure that stacks from arm64 crash dumps are usable (crbug.com/391706).
+  _default_enable_frame_pointers = true
+} else if (is_chromeos && current_cpu == "arm" && arm_use_thumb) {
+  # TODO(711784): Building ARM Thumb without frame pointers can lead to code
+  # in ChromeOS which triggers some ARM A12/A17 errata.
+  _default_enable_frame_pointers = true
 } else {
   # Explicitly ask for frame pointers, otherwise:
   # * Stacks may be missing for sanitizer and profiling builds.
   # * Debug tcmalloc can crash (crbug.com/636489).
-  # * Stacks may be missing for arm64 crash dumps (crbug.com/391706).
-  enabled_frame_pointers =
-      using_sanitizer || enable_profiling || is_debug || current_cpu == "arm64"
+  _default_enable_frame_pointers =
+      using_sanitizer || enable_profiling || is_debug
 }
 
-# Unwinding with frame pointers requires that they are enabled by default for
+declare_args() {
+  # True if frame pointers should be generated, false otherwise.
+  enable_frame_pointers = _default_enable_frame_pointers
+}
+
+# In general assume that if we have frame pointers then we can use them to
+# unwind the stack. However, this requires that they are enabled by default for
 # most translation units, that they are emitted correctly, and that the
 # compiler or platform provides a way to access them.
+can_unwind_with_frame_pointers = enable_frame_pointers
 if (current_cpu == "arm" && arm_use_thumb) {
-  # ARM Thumb builds do not emit frame pointers correctly.
+  # We cannot currently unwind ARM Thumb frame pointers correctly.
   can_unwind_with_frame_pointers = false
 } else if (is_win) {
   # Windows 32-bit does provide frame pointers, but the compiler does not
   # provide intrinsics to access them, so we don't use them.
   can_unwind_with_frame_pointers = false
-} else {
-  can_unwind_with_frame_pointers = enabled_frame_pointers
 }
 
+assert(!can_unwind_with_frame_pointers || enable_frame_pointers)
+
 declare_args() {
   # Whether or not the official builds should be built with full WPO. Enabled by
   # default for the PGO and the x64 builds.
   if (chrome_pgo_phase > 0) {
     full_wpo_on_official = true
   } else {
     full_wpo_on_official = false
   }
 }
 
@@ skipping 49 matching lines @@
 }
 
 # Assert that the configuration isn't going to hit https://crbug.com/648948.
 assert(ignore_elf32_limitations || !is_android ||
            (android_64bit_target_cpu && !build_apk_secondary_abi) ||
            is_component_build || symbol_level < 2,
        "Android 32-bit non-component builds cannot have symbol_level=2 " +
            "due to 4GiB file size limit, see https://crbug.com/648948. " +
            "If you really want to try this out, " +
            "set ignore_elf32_limitations=true.")