[GN]: BUILD file housecleaning

+ Turn on precompiled headers on Mac.
+ Change the toolchains to use asmflags instead of cflags and cflags_c.
+ Remove a TODO to hardcode the Mac SDK since the location of the SDK is not always guaranteed (on bots, for example).
+ GN: .S or .asm files no longer trigger cflags or cflags_c to be written to the ninja file.

BUG=none

Review URL: https://codereview.chromium.org/1368223002

Cr-Original-Commit-Position: refs/heads/master@{#351202}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 7a73be6eb4963662a1e9455dcdab0d5130324901

config/BUILD.gn

@@ -449,9 +449,7 @@ config("precompiled_headers") {
     # then delete the precompile.c.obj file, then build again.
     cflags_c = [ "/wd4206" ]
   } else if (is_mac && !is_official_build && !use_goma) {
-    # TODO(andybons): enable this when GCC PCH support in the binary has been
-    # rolled.
-    #precompiled_header = "build/precompile.h"
-    #precompiled_source = "//build/precompile.h"
+    precompiled_header = "build/precompile.h"
+    precompiled_source = "//build/precompile.h"
   }
 }

config/android/BUILD.gn

@@ -115,6 +115,10 @@ config("compiler") {
       abi_target,
     ]
   }
+
+  # Assign any flags set for the C compiler to asmflags so that they are sent
+  # to the assembler.
+  asmflags = cflags
 }
 
 # This is included by reference in the //build/config/compiler:runtime_library
@@ -194,6 +198,7 @@ config("runtime_library") {
 config("sdk") {
   if (sysroot != "") {
     cflags = [ "--sysroot=" + sysroot ]
+    asmflags = [ "--sysroot=" + sysroot ]
     ldflags = [ "--sysroot=" + sysroot ]
 
     # Need to get some linker flags out of the sysroot.
@@ -209,6 +214,7 @@ config("sdk") {
 
 config("executable_config") {
   cflags = [ "-fPIE" ]
+  asmflags = [ "-fPIE" ]
   ldflags = [ "-pie" ]
 }
 

config/compiler/BUILD.gn

@@ -93,6 +93,7 @@ config("default_include_dirs") {
 # where stuff should go. Put warning related stuff in the "warnings" config.
 
 config("compiler") {
+  asmflags = []
   cflags = []
   cflags_c = []
   cflags_cc = []
@@ -453,11 +454,20 @@ config("compiler") {
   # Pass the same C/C++ flags to the objective C/C++ compiler.
   cflags_objc += cflags_c
   cflags_objcc += cflags_cc
+
+  # Assign any flags set for the C compiler to asmflags so that they are sent
+  # to the assembler. The Windows assembler takes different types of flags
+  # so only do so for posix platforms.
+  if (is_posix) {
+    asmflags += cflags
+    asmflags += cflags_c
+  }
 }
 
 config("compiler_arm_fpu") {
   if (current_cpu == "arm" && !is_ios && !is_nacl) {
     cflags = [ "-mfpu=$arm_fpu" ]
+    asmflags = cflags
   }
 }
 
@@ -806,6 +816,7 @@ config("no_chromium_code") {
       "-Wno-deprecated",
     ]
   }
+
   cflags += default_warning_flags
   cflags_cc += default_warning_flags_cc
 }
@@ -1083,6 +1094,7 @@ config("symbols") {
     if (use_debug_fission) {
       cflags += [ "-gsplit-dwarf" ]
     }
+    asmflags = cflags
     ldflags = []
   }
 }
@@ -1105,6 +1117,7 @@ config("minimal_symbols") {
     if (use_debug_fission) {
       cflags += [ "-gsplit-dwarf" ]
     }
+    asmflags = cflags
     ldflags = []
   }
 }
@@ -1113,6 +1126,7 @@ config("minimal_symbols") {
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
+    asmflags = cflags
   }
 }
 

config/mac/BUILD.gn

@@ -12,6 +12,7 @@ config("sdk") {
     "-mmacosx-version-min=$mac_deployment_target",
   ]
 
+  asmflags = common_flags
   cflags = common_flags
   ldflags = common_flags
 }

config/mac/mac_sdk.gni

@@ -34,11 +34,5 @@ find_sdk_lines =
     exec_script("//build/mac/find_sdk.py", find_sdk_args, "list lines")
 mac_sdk_version = find_sdk_lines[1]
 if (mac_sdk_path == "") {
-  # TODO(brettw) http://crbug.com/335325  when everybody moves to XCode 5 we
-  # can remove the --print_sdk_path argument to find_sdk and instead just use
-  # the following two lines to get the path. Although it looks longer here, it
-  # saves forking a process in find_sdk.py so will be faster.
-  #mac_sdk_root = "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX"
-  #mac_sdk_path = mac_sdk_root + mac_sdk_version + ".sdk"
   mac_sdk_path = find_sdk_lines[0]
 }

config/win/BUILD.gn

@@ -12,6 +12,14 @@ assert(is_win)
 # is applied to all targets. It is here to separate out the logic that is
 # Windows-only.
 config("compiler") {
+  asmflags = [
+    # When /SAFESEH is specified, the linker will only produce an image if it
+    # can also produce a table of the image's safe exception handlers. This
+    # table specifies for the operating system which exception handlers are
+    # valid for the image.
+    "/SAFESEH",
+  ]
+
   cflags = [
     "/Gy",  # Enable function-level linking.
     "/GS",  # Enable buffer security checking.

toolchain/gcc_toolchain.gni

@@ -194,7 +194,7 @@ template("gcc_toolchain") {
     tool("asm") {
       # For GCC we can just use the C compiler to compile assembly.
       depfile = "{{output}}.d"
-      command = "$cc -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
+      command = "$cc -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "ASM {{output}}"
       outputs = [

toolchain/mac/BUILD.gn

@@ -50,10 +50,7 @@ template("mac_toolchain") {
 
     tool("cc") {
       depfile = "{{output}}.d"
-
-      # TODO(andybons): enable this when GCC PCH support in the binary has been
-      # rolled.
-      #precompiled_header_type = "gcc"
+      precompiled_header_type = "gcc"
       command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CC {{output}}"
@@ -64,10 +61,7 @@ template("mac_toolchain") {
 
     tool("cxx") {
       depfile = "{{output}}.d"
-
-      # TODO(andybons): enable this when GCC PCH support in the binary has been
-      # rolled.
-      #precompiled_header_type = "gcc"
+      precompiled_header_type = "gcc"
       command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CXX {{output}}"
@@ -79,7 +73,7 @@ template("mac_toolchain") {
     tool("asm") {
       # For GCC we can just use the C compiler to compile assembly.
       depfile = "{{output}}.d"
-      command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
+      command = "$cc -MMD -MF $depfile {{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "ASM {{output}}"
       outputs = [
@@ -90,10 +84,7 @@ template("mac_toolchain") {
     tool("objc") {
       depfile = "{{output}}.d"
       command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_objc}} -c {{source}} -o {{output}}"
-
-      # TODO(andybons): enable this when GCC PCH support in the binary has been
-      # rolled.
-      #precompiled_header_type = "gcc"
+      precompiled_header_type = "gcc"
       command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} {{cflags_objc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "OBJC {{output}}"
@@ -105,10 +96,7 @@ template("mac_toolchain") {
     tool("objcxx") {
       depfile = "{{output}}.d"
       command = "$cxx -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_objcc}} -c {{source}} -o {{output}}"
-
-      # TODO(andybons): enable this when GCC PCH support in the binary has been
-      # rolled.
-      #precompiled_header_type = "gcc"
+      precompiled_header_type = "gcc"
       depsformat = "gcc"
       description = "OBJCXX {{output}}"
       outputs = [

toolchain/win/BUILD.gn

@@ -120,9 +120,7 @@ template("msvc_toolchain") {
     }
 
     tool("asm") {
-      # TODO(brettw): "/safeseh" assembler argument is hardcoded here. Extract
-      # assembler flags to a variable like cflags. crbug.com/418613
-      command = "$python_path gyp-win-tool asm-wrapper $env ml.exe {{defines}} {{include_dirs}} /safeseh /c /Fo {{output}} {{source}}"
+      command = "$python_path gyp-win-tool asm-wrapper $env ml.exe {{defines}} {{include_dirs}} {{asmflags}} /c /Fo{{output}} {{source}}"
       description = "ASM {{output}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}/{{source_name_part}}.obj",