[Chromecast] Only include all libstdc++/libgcc symbols in executable as needed

build/config/chromecast/BUILD.gn

 # 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/chromecast_build.gni")
 
 assert(is_chromecast)
 
 config("static_config") {
   ldflags = [
@@ skipping 16 matching lines @@
   # This is explicitly disabled in Chrome for security reasons (see comments in
   # //build/config/gcc/BUILD.gn), but necessary on Chromecast so that OEM's may
   # override the default libraries shipped in the Cast receiver package.
   ldflags = [
     "-Wl,-rpath=/oem_cast_shlib",
     "-Wl,-rpath=\$ORIGIN/lib",
     "-Wl,-rpath=\$ORIGIN",
   ]
 }
 
+# whole archiving libgcc.a and libstdc++ is needed if dynamic share libs are
+# used, see b/25566835
+config("executable_whole_archive_config") {
+  if (current_cpu == "arm") {
+    ldflags = [
+      # adding all symbols from libgcc and libstdc++
+      "-Wl,--whole-archive",
+      "-l:libstdc++.a",
+      "-l:libgcc.a",
+      "-Wl,--no-whole-archive",
+    ]
+  }
+}
+
 config("executable_config") {
   configs = [ ":ldconfig" ]
 
   if (current_cpu == "arm") {

[bcf, 2016/08/29 21:22:51]

You should be able to move this whole block to executable_whole_archive_config,
which will help save some more size.

[antz1, 2016/08/29 23:09:33]

Done.

     ldflags = [
       # Export stdlibc++ and libgcc symbols to force shlibs to refer to these
       # symbols from the executable.
       "-Wl,--export-dynamic",
 
       "-lm",  # stdlibc++ requires math.h
 
       # In case we redefined stdlibc++ symbols (e.g. tc_malloc)
       "-Wl,--allow-multiple-definition",
-
-      "-Wl,--whole-archive",
-      "-l:libstdc++.a",
-      "-l:libgcc.a",
-      "-Wl,--no-whole-archive",
     ]
 
     # Despite including libstdc++/libgcc archives, we still need to specify
     # static linking for them in order to prevent the executable from having a
     # dynamic dependency on them.
     configs += [ ":static_config" ]
   }
 }
 
 config("shared_library_config") {
   configs = [ ":ldconfig" ]
   if (current_cpu == "arm") {
     configs += [ ":static_config" ]
   }
 }