[Mac/GN] Implement dSYM generation and stripping.

build/toolchain/mac/BUILD.gn

 # 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.
 
 # TODO(brettw) Use "gcc_toolchain.gni" like the Linux toolchains. This requires
 # some enhancements since the commands on Mac are slightly different than on
 # Linux.
 
 import("../goma.gni")
 import("//build/config/ios/ios_sdk.gni")
@@ skipping 120 matching lines @@
       # the existing .TOC file, overwrite it, otherwise, don't change it.
       #
       # As a special case, if the library reexports symbols from other dynamic
       # libraries, we always update the .TOC and skip the temporary file and
       # diffing steps, since that library always needs to be re-linked.
       tocname = dylib + ".TOC"
       temporary_tocname = dylib + ".tmp"
 
       does_reexport_command = "[ ! -e \"$dylib\" -o ! -e \"$tocname\" ] || otool -l \"$dylib\" | grep -q LC_REEXPORT_DYLIB"
 
-      link_command = "$ld -shared "
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)

[Dirk Pranke, 2016/05/20 01:47:19]

You should be able to hoist this up into a file-scoped variable, rather than
having to repeat it three times.

[Robert Sesek, 2016/05/20 15:15:36]

I tried doing it at the file-level but GN complained it was unused. Moved it up
into the toolchain, though.

[Dirk Pranke, 2016/05/20 16:43:55]

Oh, yeah, usage doesn't propagate across templates. Well, into the template is
good enough.

+
+      link_command = "$linker_driver $ld -shared "
       if (is_component_build) {
         link_command += " -Wl,-install_name,@rpath/\"{{target_output_name}}{{output_extension}}\" "
       }
       link_command += "{{ldflags}} -o \"$dylib\" -Wl,-filelist,\"$rspfile\" {{libs}} {{solibs}}"
 
       replace_command = "if ! cmp -s \"$temporary_tocname\" \"$tocname\"; then mv \"$temporary_tocname\" \"$tocname\""
       extract_toc_command = "{ otool -l \"$dylib\" | grep LC_ID_DYLIB -A 5; nm -gP \"$dylib\" | cut -f1-2 -d' ' | grep -v U\$\$; true; }"
 
       command = "if $does_reexport_command ; then $link_command && $extract_toc_command > \"$tocname\"; else $link_command && $extract_toc_command > \"$temporary_tocname\" && $replace_command ; fi; fi"
 
       rspfile_content = "{{inputs_newline}}"
 
       description = "SOLINK {{output}}"
 
       # 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_dir = "{{root_out_dir}}"
       default_output_extension = ".dylib"
 
       output_prefix = "lib"
 
       # Since the above commands only updates the .TOC file when it changes, ask
       # Ninja to check if the timestamp actually changed to know if downstream
       # dependencies should be recompiled.
       restat = true
 
       # Tell GN about the output files. It will link to the dylib but use the
       # tocname for dependency management.
       outputs = [

[Robert Sesek, 2016/05/19 22:38:59]

The major issue I see is that we're not listing the dSYM as an output.

[Dirk Pranke, 2016/05/20 01:47:19]

Can you do something like:

    if (enable_dsyms) {
        outputs += [ "{{target_output_name}}.dSYM/" ]
    }

or some such?

[Robert Sesek, 2016/05/20 15:15:36]

As written, we don't generate dSYMs for every target, since doing so is super
slow. We're only doing it for the build products that we strip and ship.

[Dirk Pranke, 2016/05/20 16:43:55]

Ah, true. Hmm ...

[Robert Sesek, 2016/05/24 15:05:32]

Mark: What if we created fake dSYMs again? We could toggle full/real dSYMs on a
per-target basis, but if enable_dsyms = true, everything would get a fake dSYM
by default.

[Mark Mentovai, 2016/05/24 18:24:32]

I would prefer not to. The fake .dSYMs were just garbage. Nothing in the modern
toolchain could do anything useful with them.

Now that dsymutil is really llvm-dsymutil, and most developers are on the (ugh)
component=shared_library build, is doing real .dSYMs everywhere (in a Release
build) still a problem? Note that I’m fully expecting the answer to be “no,” but
I gotta ask.

[Robert Sesek, 2016/05/24 18:28:23]

In GN land, enable_dsyms is by default tied to is_official_build. I guess we
could just dSYM all the things in this mode. It may slow down the official
builders for generating dSYMs for test targets, but I don't think it'd have any
impact on developer or non-official bots. (And if it does, developers can just
manually turn off enable_dsyms).

         dylib,
         tocname,
       ]
       link_output = dylib
       depend_output = tocname
     }
 
     tool("solink_module") {
       sofile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # eg "./libfoo.so"
       rspfile = sofile + ".rsp"
 
-      link_command =
-          "$ld -bundle {{ldflags}} -o \"$sofile\" -Wl,-filelist,\"$rspfile\""
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)
+
+      link_command = "$linker_driver $ld -bundle {{ldflags}} -o \"$sofile\" -Wl,-filelist,\"$rspfile\""
       if (is_component_build) {
         link_command += " -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
       }
       link_command += " {{solibs}} {{libs}}"
       command = link_command
 
       rspfile_content = "{{inputs_newline}}"
 
       description = "SOLINK_MODULE {{output}}"
 
@@ skipping 13 matching lines @@
       rspfile = "$outfile.rsp"
 
       # Note about --filelist: Apple's linker reads the file list file and
       # interprets each newline-separated chunk of text as a file name. It
       # doesn't do the things one would expect from the shell like unescaping
       # or handling quotes. In contrast, when Ninja finds a file name with
       # spaces, it single-quotes them in $inputs_newline as it would normally
       # do for command-line arguments. Thus any source names with spaces, or
       # label names with spaces (which GN bases the output paths on) will be
       # corrupted by this process. Don't use spaces for source files or labels.
-      command = "$ld {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)
+
+      command = "$linker_driver $ld {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
       description = "LINK $outfile"
       rspfile_content = "{{inputs_newline}}"
       outputs = [
         outfile,
       ]
 
       default_output_dir = "{{root_out_dir}}"
     }
 
     # These two are really entirely generic, but have to be repeated in
@@ skipping 127 matching lines @@
 }
 
 mac_toolchain("x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
   cc = "${goma_prefix}/gcc"
   cxx = "${goma_prefix}/g++"
   ld = cxx
   is_clang = false
 }