GN: Use lib.unstripped rather than lib.stripped. Add a toolchain.gni

toolchain.gni introduces:
 root_shlib_dir, shlib_prefix, and shlib_extension

The original goal of this change was to put shlibs under lib/ for Linux / Android, since that's where GYP puts them. However, the lack of support for loadable_module (or more specifically - per target output directory) in GN makes this infeasible at the moment.

This change also mitigates a subtle bug where on Android the unstripped .so is used mistakenly instead of the lib.stripped/ version. It also fixes shlib's link_output being set to the unstripped .so rather than the stripped .so (on Android).

BUG=509771

Review URL: https://codereview.chromium.org/1236503002

Cr-Commit-Position: refs/heads/master@{#342697}

4 files changed, 81 insertions, 39 deletions

diff --git a/build/toolchain/android/BUILD.gn b/build/toolchain/android/BUILD.gn
index 867fa48..ed7c407 100644
--- a/build/toolchain/android/BUILD.gn
+++ b/build/toolchain/android/BUILD.gn
@@ -64,32 +64,10 @@ template("android_gcc_toolchain") {
     ld = cxx
     readelf = compiler_prefix + tool_prefix + "readelf"
     nm = compiler_prefix + tool_prefix + "nm"
+    strip = "${tool_prefix}strip"
 
     toolchain_os = "android"
     toolchain_cpu = invoker.toolchain_cpu
-
-    # We make the assumption that the gcc_toolchain will produce a soname with
-    # the following definition.
-    soname = "{{target_output_name}}{{output_extension}}"
-
-    stripped_soname = "lib.stripped/${soname}"
-    temp_stripped_soname = "${stripped_soname}.tmp"
-
-    android_strip = "${tool_prefix}strip"
-
-    strip_command =
-        "$android_strip --strip-unneeded -o $temp_stripped_soname $soname"
-    replace_command = "if ! cmp -s $temp_stripped_soname $stripped_soname; then mv $temp_stripped_soname $stripped_soname; fi"
-    postsolink = "$strip_command && $replace_command"
-    solink_outputs = [ stripped_soname ]
-    default_output_extension = android_product_extension
-
-    # We make the assumption that the gcc_toolchain will produce an exe with
-    # the following definition.
-    exe = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
-    stripped_exe = "exe.stripped/$exe"
-    postlink = "$android_strip --strip-unneeded -o $stripped_exe $exe"
-    link_outputs = [ stripped_exe ]
   }
 }
 
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index 29b9137..14a66e4 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/toolchain/toolchain.gni")
+
 # This value will be inherited in the toolchain below.
 concurrent_links = exec_script("get_concurrent_links.py", [], "value")
 
@@ -34,6 +36,11 @@ concurrent_links = exec_script("get_concurrent_links.py", [], "value")
 #  - deps
 #      Just forwarded to the toolchain definition.
 #  - is_clang
+#      Whether to use clang instead of gcc.
+#  - strip
+#      Location of the strip executable. When specified, strip will be run on
+#      all shared libraries and executables as they are built. The pre-stripped
+#      artifacts will be put in lib.stripped/ and exe.stripped/.
 template("gcc_toolchain") {
   toolchain(target_name) {
     assert(defined(invoker.cc), "gcc_toolchain() must specify a \"cc\" value")
@@ -138,24 +145,34 @@ template("gcc_toolchain") {
     tool("solink") {
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
+      if (shlib_subdir != ".") {
+        sofile = "{{root_out_dir}}/$shlib_subdir/$soname"
+      }
       rspfile = sofile + ".rsp"
 
+      unstripped_sofile = sofile
+      if (defined(invoker.strip)) {
+        unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
+      }
+
       # These variables are not built into GN but are helpers that implement
       # (1) linking to produce a .so, (2) extracting the symbols from that file
       # to a temporary file, (3) if the temporary file has differences from the
       # existing .TOC file, overwrite it, otherwise, don't change it.
       tocfile = sofile + ".TOC"
       temporary_tocname = sofile + ".tmp"
-      link_command =
-          "$ld -shared {{ldflags}} -o $sofile -Wl,-soname=$soname @$rspfile"
+
+      link_command = "$ld -shared {{ldflags}} -o $unstripped_sofile -Wl,-soname=$soname @$rspfile"
       assert(defined(readelf), "to solink you must have a readelf")
       assert(defined(nm), "to solink you must have an nm")
-      toc_command = "{ $readelf -d $sofile | grep SONAME ; $nm -gD -f p $sofile | cut -f1-2 -d' '; } > $temporary_tocname"
+      toc_command = "{ $readelf -d $unstripped_sofile | grep SONAME ; $nm -gD -f p $unstripped_sofile | cut -f1-2 -d' '; } > $temporary_tocname"
       replace_command = "if ! cmp -s $temporary_tocname $tocfile; then mv $temporary_tocname $tocfile; fi"
 
       command = "$link_command && $toc_command && $replace_command"
-      if (defined(invoker.postsolink)) {
-        command += " && " + invoker.postsolink
+      if (defined(invoker.strip)) {
+        strip_command =
+            "${invoker.strip} --strip-unneeded -o $sofile $unstripped_sofile"
+        command += " && " + strip_command
       }
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
 
@@ -164,7 +181,7 @@ template("gcc_toolchain") {
       # 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 = ".so"
+      default_output_extension = shlib_extension
       if (defined(invoker.default_output_extension)) {
         default_output_extension = invoker.default_output_extension
       }
@@ -182,27 +199,35 @@ template("gcc_toolchain") {
         sofile,
         tocfile,
       ]
-      if (defined(invoker.solink_outputs)) {
-        outputs += invoker.solink_outputs
+      if (sofile != unstripped_sofile) {
+        outputs += [ unstripped_sofile ]
       }
       link_output = sofile
       depend_output = tocfile
     }
 
     tool("link") {
-      outfile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
+      exename = "{{target_output_name}}{{output_extension}}"
+      outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"
-      command = "$ld {{ldflags}} -o $outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
-      if (defined(invoker.postlink)) {
-        command += " && " + invoker.postlink
+      unstripped_outfile = outfile
+      if (defined(invoker.strip)) {
+        unstripped_outfile = "{{root_out_dir}}/exe.unstripped/$exename"
+      }
+
+      command = "$ld {{ldflags}} -o $unstripped_outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
+      if (defined(invoker.strip)) {
+        strip_command =
+            "${invoker.strip} --strip-unneeded -o $outfile $unstripped_outfile"
+        command += " && " + strip_command
       }
       description = "LINK $outfile"
       rspfile_content = "{{inputs}}"
       outputs = [
         outfile,
       ]
-      if (defined(invoker.link_outputs)) {
-        outputs += invoker.link_outputs
+      if (outfile != unstripped_outfile) {
+        outputs += [ unstripped_outfile ]
       }
     }
 
diff --git a/build/toolchain/toolchain.gni b/build/toolchain/toolchain.gni
new file mode 100644
index 0000000..5bd7d9c
--- /dev/null
+++ b/build/toolchain/toolchain.gni
@@ -0,0 +1,40 @@
+# 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.
+
+# Toolchain-related configuration that may be needed outside the context of the
+# toolchain() rules themselves.
+
+# Subdirectory within root_out_dir for shared library files.
+# TODO(agrieve): GYP sets this to "lib" for Linux & Android, but this won't work
+#     in GN until support for loadable_module() is added.
+#     See: https://codereview.chromium.org/1236503002/
+shlib_subdir = "."
+
+# Root out dir for shared library files.
+root_shlib_dir = root_out_dir
+if (shlib_subdir != ".") {
+  root_shlib_dir += "/$shlib_subdir"
+}
+
+# Extension for shared library files (including leading dot).
+if (is_mac || is_ios) {
+  shlib_extension = ".dylib"
+} else if (is_android && is_component_build) {
+  # By appending .cr, we prevent name collisions with libraries already
+  # loaded by the Android zygote.
+  shlib_extension = ".cr.so"
+} else if (is_posix) {
+  shlib_extension = ".so"
+} else if (is_win) {
+  shlib_extension = ".dll"
+} else {
+  assert(false, "Platform not supported")
+}
+
+# Prefix for shared library files.
+if (is_posix) {
+  shlib_prefix = "lib"
+} else {
+  shlib_prefix = ""
+}
diff --git a/build/toolchain/win/BUILD.gn b/build/toolchain/win/BUILD.gn
index 6c3e06b..a054267 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -147,8 +147,7 @@ template("msvc_toolchain") {
 
     tool("solink") {
       dllname = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"  # e.g. foo.dll
-      libname =
-          "{{root_out_dir}}/{{target_output_name}}{{output_extension}}.lib"  # e.g. foo.dll.lib
+      libname = "${dllname}.lib"  # e.g. foo.dll.lib
       rspfile = "${dllname}.rsp"
 
       link_command = "$python_path gyp-win-tool link-wrapper $env False link.exe /nologo /IMPLIB:$libname /DLL /OUT:$dllname /PDB:${dllname}.pdb @$rspfile"