Output a linker map file for official builds

build/toolchain/gcc_toolchain.gni

 # Copyright (c) 2013 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/clang/clang.gni")
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//build/toolchain/cc_wrapper.gni")
@@ skipping 301 matching lines @@
       }
 
       # These variables are not built into GN but are helpers that
       # implement (1) linking to produce a .so, (2) extracting the symbols
       # from that file (3) if the extracted list differs from the existing
       # .TOC file, overwrite it, otherwise, don't change it.
       tocfile = sofile + ".TOC"
 
       link_command = "$ld -shared {{ldflags}}${extra_ldflags} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""
 
+      # Generate a map file to be used for binary size analysis.
+      # Map file adds ~10% to the link time on a z620.
+      # With target_os="android", libchrome.so.map.gz is ~20MB.
+      map_switch = ""
+      if (is_official_build) {

[Dirk Pranke, 2017/03/03 21:38:48]

This'll affect linux and chromeos too, right? Is that intentional? For Linux,
due to LTO, a 10% impact is not small.

[agrieve, 2017/03/04 02:01:26]

It was intentional, since the size analysis tool should work just the same on
these other platforms as well.

On one hand, I can certainly get quite far by making this android only.
OTOH, my 10% number came from adding 3 seconds to my 30 second link. I suspect
it would also add around 3 seconds to an lto link, which wouldn't be too bad.

+        map_switch = "--mapfile \"$unstripped_sofile.map.gz\" "
+      }
+
       assert(defined(readelf), "to solink you must have a readelf")
       assert(defined(nm), "to solink you must have an nm")
       strip_switch = ""
       if (defined(invoker.strip)) {
-        strip_switch = "--strip=${invoker.strip}"
+        strip_switch = "--strip=${invoker.strip} "
       }
 
       # This needs a Python script to avoid using a complex shell command
       # requiring sh control structures, pipelines, and POSIX utilities.
       # The host might not have a POSIX shell and utilities (e.g. Windows).
       solink_wrapper = rebase_path("//build/toolchain/gcc_solink_wrapper.py")
-      command = "$python_path \"$solink_wrapper\" --readelf=\"$readelf\" --nm=\"$nm\" $strip_switch --sofile=\"$unstripped_sofile\" --tocfile=\"$tocfile\" --output=\"$sofile\"$whitelist_flag -- $link_command"
+      command = "$python_path \"$solink_wrapper\" --readelf=\"$readelf\" --nm=\"$nm\" $strip_switch--sofile=\"$unstripped_sofile\" --tocfile=\"$tocfile\" $map_switch--output=\"$sofile\"$whitelist_flag -- $link_command"
 
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
 
       description = "SOLINK $sofile"
 
       # Use this for {{output_extension}} expansions unless a target manually
       # overrides it (in which case {{output_extension}} will be what the target
       # specifies).
       default_output_extension = default_shlib_extension
 
@@ skipping 170 matching lines @@
     forward_variables_from(invoker, [ "strip" ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
   }
 }