patch from chinmaygarde@ to make progress on mac, ios.

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")
 
 assert(host_os == "mac")
 
 import("//build/toolchain/clang.gni")
 import("//build/toolchain/goma.gni")
+import("//build/config/sysroot.gni")
 
 if (use_goma) {
   goma_prefix = "$goma_dir/gomacc "
 } else {
   goma_prefix = ""
 }
 
 # This will copy the gyp-mac-tool to the build directory. We pass in the source
 # file of the win tool.
 gyp_mac_tool_source =
     rebase_path("//tools/gyp/pylib/gyp/mac_tool.py", root_build_dir)
 exec_script("setup_toolchain.py", [ gyp_mac_tool_source ])
 
 # Shared toolchain definition. Invocations should set toolchain_os to set the
 # build args in this definition.
 template("mac_toolchain") {
   toolchain(target_name) {
     assert(defined(invoker.cc), "mac_toolchain() must specify a \"cc\" value")
     assert(defined(invoker.cxx), "mac_toolchain() must specify a \"cxx\" value")
     assert(defined(invoker.ld), "mac_toolchain() must specify a \"ld\" value")
     assert(defined(invoker.toolchain_cpu),
            "mac_toolchain() must specify a \"toolchain_cpu\"")
     assert(defined(invoker.toolchain_os),
            "mac_toolchain() must specify a \"toolchain_os\"")
+    assert(defined(invoker.switch_sysroot),
+           "mac_toolchain() must specify a \"switch_sysroot\"")
 
     # We can't do string interpolation ($ in strings) on things with dots in
     # them. To allow us to use $cc below, for example, we create copies of
     # these values in our scope.
     cc = invoker.cc
     cxx = invoker.cxx
     ld = invoker.ld
 
     # Make these apply to all tools below.
     lib_switch = "-l"
     lib_dir_switch = "-L"
 
+    sysroot_flags = ""
+
+    if (invoker.switch_sysroot) {
+      version_flags = ""
+
+      if (use_ios_simulator) {
+        version_flags = "-mios-simulator-version-min=$ios_deployment_target"
+      } else {
+        version_flags = "-miphoneos-version-min=$ios_deployment_target"
+      }
+
+      sysroot_flags = "-isysroot $sysroot $version_flags"
+    }
+
     tool("cc") {
       depfile = "{{output}}.d"
-      command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
+      command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} $sysroot_flags {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CC {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.o",
       ]
     }
 
     tool("cxx") {
       depfile = "{{output}}.d"
-      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
+      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} $sysroot_flags {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CXX {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.o",
       ]
     }
 
     tool("asm") {
       # For GCC we can just use the C compiler to compile assembly.
       depfile = "{{output}}.d"
       command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "ASM {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.o",
       ]
     }
 
     tool("objc") {
       depfile = "{{output}}.d"
-      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_objc}} -c {{source}} -o {{output}}"
+      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} {{cflags_objc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "OBJC {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.o",
       ]
     }
 
     tool("objcxx") {
       depfile = "{{output}}.d"
-      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_objcc}} -c {{source}} -o {{output}}"
+      command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} {{cflags_objcc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "OBJCXX {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.o",
       ]
     }
 
     tool("alink") {
       command = "rm -f {{output}} && ./gyp-mac-tool filter-libtool libtool -static -o {{output}} {{inputs}}"
       description = "LIBTOOL-STATIC {{output}}"
@@ skipping 13 matching lines @@
       # to a temporary file, (3) if the temporary file has differences from the
       # existing .TOC file, overwrite it, oterwise, 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 {{ldflags}} -o $dylib -Wl,-filelist,$rspfile {{solibs}} {{libs}}"
+      link_command = "$ld -shared $sysroot_flags {{ldflags}} -o $dylib -Wl,-filelist,$rspfile {{solibs}} {{libs}}"
       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
@@ skipping 14 matching lines @@
         dylib,
         tocname,
       ]
       link_output = dylib
       depend_output = tocname
     }
 
     tool("link") {
       outfile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
-      command = "$ld {{ldflags}} -o $outfile -Wl,-filelist,$rspfile {{solibs}} {{libs}}"
+      command = "$ld $sysroot_flags {{ldflags}} -o $outfile -Wl,-filelist,$rspfile {{solibs}} {{libs}}"
       description = "LINK $outfile"
       rspfile_content = "{{inputs_newline}}"
       outputs = [
         outfile,
       ]
     }
 
     tool("stamp") {
       command = "touch {{output}}"
       description = "STAMP {{output}}"
@@ skipping 21 matching lines @@
 
 mac_toolchain("clang_arm") {
   toolchain_cpu = "arm"
   toolchain_os = "mac"
   prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
                        root_build_dir)
   cc = "${goma_prefix}$prefix/clang"
   cxx = "${goma_prefix}$prefix/clang++"
   ld = cxx
   is_clang = true
+  switch_sysroot = false
+}
+
+mac_toolchain("ios_clang_arm") {

[sdefresne, 2015/07/25 19:15:30]

do we need "ios_clang_armv7" and "ios_clang_arm64"?

+  toolchain_cpu = "arm"
+  toolchain_os = "mac"
+  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",

[sdefresne, 2015/07/25 19:15:30]

Question: with gyp, at multiple occasion, on iOS we had to use the version of
clang shipped with Xcode (due to features added by Apple to their version of
clang, and only landing a few weeks or months later in the open-source version
of clang).

Can we add the support for this with gn too?

[Dirk Pranke, 2015/07/31 21:27:41]

We can definitely add it. I'll add a TODO here.

+                       root_build_dir)
+  cc = "${goma_prefix}$prefix/clang"
+  cxx = "${goma_prefix}$prefix/clang++"
+  ld = cxx
+  is_clang = true
+  switch_sysroot = true
 }
 
 mac_toolchain("arm") {
   toolchain_cpu = "arm"
   toolchain_os = "mac"
   cc = "${goma_prefix}/gcc"
   cxx = "${goma_prefix}/g++"
   ld = cxx
   is_clang = false
+  switch_sysroot = false
 }
 
 mac_toolchain("clang_x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
   prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
                        root_build_dir)
   cc = "${goma_prefix}$prefix/clang"
   cxx = "${goma_prefix}$prefix/clang++"
   ld = cxx
   is_clang = true
+  switch_sysroot = false
 }
 
 mac_toolchain("x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
   cc = "${goma_prefix}/gcc"
   cxx = "${goma_prefix}/g++"
   ld = cxx
   is_clang = false
+  switch_sysroot = false
 }