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 196 matching lines @@
     } else {
       extra_cxxflags = ""
     }
 
     if (defined(invoker.extra_ldflags) && invoker.extra_ldflags != "") {
       extra_ldflags = " " + invoker.extra_ldflags
     } else {
       extra_ldflags = ""
     }
 
+    enable_linker_map =
+        defined(invoker.enable_linker_map) && invoker.enable_linker_map
+
     # These library switches can apply to all tools below.
     lib_switch = "-l"
     lib_dir_switch = "-L"
 
     # Object files go in this directory.
     object_subdir = "{{target_out_dir}}/{{label_name}}"
 
     tool("cc") {
       depfile = "{{output}}.d"
       command = "$cc -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{cflags}} {{cflags_c}}${extra_cppflags}${extra_cflags} -c {{source}} -o {{output}}"
@@ skipping 85 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 (enable_linker_map && is_official_build) {
+        map_file = "$unstripped_sofile.map.gz"
+        map_switch = " --map-file \"$map_file\""
+      }
+
       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 14 matching lines @@
       outputs = [
         sofile,
         tocfile,
       ]
       if (enable_resource_whitelist_generation) {
         outputs += [ whitelist_file ]
       }
       if (sofile != unstripped_sofile) {
         outputs += [ unstripped_sofile ]
       }
+      if (defined(map_file)) {
+        outputs += [ map_file ]
+      }
       link_output = sofile
       depend_output = tocfile
     }
 
     tool("solink_module") {
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{output_dir}}/$soname"
       rspfile = sofile + ".rsp"
       pool = "//build/toolchain:link_pool($default_toolchain)"
 
@@ skipping 48 matching lines @@
       # overrides it (in which case {{output_extension}} will be what the target
       # specifies).
       default_output_extension = default_executable_extension
 
       default_output_dir = "{{root_out_dir}}"
 
       if (defined(invoker.strip)) {
         unstripped_outfile = "{{root_out_dir}}/exe.unstripped/$exename"
       }
 
-      command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" -Wl,--start-group @\"$rspfile\" {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
+      # Generate a map file to be used for binary size analysis.
+      # Map file adds ~10% to the link time on a z620.
+      # With target_os="android", libchrome.so.map.gz is ~20MB.
+      map_switch = ""
+      if (enable_linker_map && is_official_build) {
+        map_file = "$unstripped_outfile.map.gz"
+        map_switch = " --map-file \"$map_file\""
+      }
+
+      link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" -Wl,--start-group @\"$rspfile\" {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
+
+      strip_switch = ""
       if (defined(invoker.strip)) {
-        link_wrapper =
-            rebase_path("//build/toolchain/gcc_link_wrapper.py", root_build_dir)
-        command = "$python_path \"$link_wrapper\" --strip=\"${invoker.strip}\" --unstripped-file=\"$unstripped_outfile\" --output=\"$outfile\" -- $command"
+        strip_switch = " --strip=\"${invoker.strip}\" --unstripped-file=\"$unstripped_outfile\""
       }
+
+      link_wrapper =
+          rebase_path("//build/toolchain/gcc_link_wrapper.py", root_build_dir)
+      command = "$python_path \"$link_wrapper\" --output=\"$outfile\"$strip_switch$map_switch -- $link_command"
       description = "LINK $outfile"
       rspfile_content = "{{inputs}}"
       outputs = [
         outfile,
       ]
       if (outfile != unstripped_outfile) {
         outputs += [ unstripped_outfile ]
       }
       if (defined(invoker.link_outputs)) {
         outputs += invoker.link_outputs
       }
+      if (defined(map_file)) {
+        outputs += [ map_file ]
+      }
     }
 
     # These two are really entirely generic, but have to be repeated in
     # each toolchain because GN doesn't allow a template to be used here.
     # See //build/toolchain/toolchain.gni for details.
     tool("stamp") {
       command = stamp_command
       description = stamp_description
     }
     tool("copy") {
@@ skipping 41 matching lines @@
                        root_build_dir)
       cxx = analyzer_wrapper + " --clang-cxx-path=${cxx} --analyzer=" +
             rebase_path("//third_party/scan-build/src/libexec/c++-analyzer",
                         root_build_dir)
     }
 
     readelf = "${toolprefix}readelf"
     ar = "${toolprefix}ar"
     nm = "${toolprefix}nm"
 
-    forward_variables_from(invoker, [ "strip" ])
+    forward_variables_from(invoker,
+                           [
+                             "enable_linker_map",
+                             "strip",
+                           ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
   }
 }