Explicitly ask for stack frame pointers on Debug posix builds.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 79723f6cc76c041697955f5c7de91e2935e78aa5..27a52235db8ba884b255ff2b4b5c253b30ac82e7 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -232,9 +232,6 @@ config("compiler") {
   # -----------------------------------
   if (is_posix && !(is_mac || is_ios)) {
     if (enable_profiling) {
-      # Explicitly ask for frame pointers. Otherwise they are omitted when
-      # any optimization level is used (and Android debug builds use -Os).
-      cflags += [ "-fno-omit-frame-pointer" ]
       if (!is_debug) {
         cflags += [ "-g" ]
 
@@ -1238,13 +1235,6 @@ if (is_win) {
   common_optimize_on_ldflags = []
 
   if (is_android) {
-    # We don't omit frame pointers on arm64 since they are required
-    # to correctly unwind stackframes which contain system library
-    # function frames (crbug.com/391706).
-    if (!using_sanitizer && !enable_profiling && current_cpu != "arm64") {
-      common_optimize_on_cflags += [ "-fomit-frame-pointer" ]
-    }
-
     # TODO(jdduke) Re-enable on mips after resolving linking
     # issues with libc++ (crbug.com/456380).
     if (current_cpu != "mipsel" && current_cpu != "mips64el") {
@@ -1298,6 +1288,21 @@ if (is_win) {
   }
 }
 
+config("default_stack_frames") {
+  if (is_posix && !(is_mac || is_ios)) {
+    if (using_sanitizer || enable_profiling || is_debug ||

[brettw, 2016/08/24 18:27:02]

This is still different from the old code on Android.

Previously on Android no_optimize would still omit frame pointers unless
!android_full_debug was set (which is what you set when you really want to
debug).

[vmiura, 2016/08/24 18:47:26]

I may be missing a nuance, but I'm intentionally making this change from the old
behavior because omitting frames on Debug can cause flaky crashes in tcmalloc. 
We run standard Debug builds on bots and I don't think we want to change them to
android_full_debug.

+        current_cpu == "arm64") {
+      # 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).
+      cflags = [ "-fno-omit-frame-pointer" ]
+    } else if (is_android) {
+      cflags = [ "-fomit-frame-pointer" ]

[brettw, 2016/08/24 19:30:02]

I mean this line. It used to not set this on the Android debug case when
android_full_debug was set.

[vmiura, 2016/08/24 19:40:16]

Thanks, yeah I think that 'android_full_debug' is only used together with
'is_debug' which triggers config("no_optimize"), so it would use the
-fno-omit-frame-pointer flag.

+    }
+  }
+}
+
 # Default "optimization on" config.
 config("optimize") {
   if (is_win) {
@@ -1357,13 +1362,6 @@ config("no_optimize") {
       "-ffunction-sections",
     ]
 
-    # We don't omit frame pointers on arm64 since they are required
-    # to correctly unwind stackframes which contain system library
-    # function frames (crbug.com/391706).
-    if (!using_sanitizer && !enable_profiling && current_cpu != "arm64") {
-      cflags += [ "-fomit-frame-pointer" ]
-    }
-
     # Don't use gc-sections since it can cause links to succeed when they
     # actually shouldn't. http://crbug.com/159847
     ldflags = common_optimize_on_ldflags - [ "-Wl,--gc-sections" ]