Separate out compiler and runtime configs on Windows and Android GN.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index e8eb59a8b08e93b35f1b69156203298d4072b29f..74dec11c3b8b645c5030e3925a0ce950d7167e6e 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -102,69 +102,18 @@ config("compiler") {
   defines = []
   configs = []
 
-  # In general, Windows is totally different, but all the other builds share
-  # some common GCC configuration. This section sets up Windows and the common
-  # GCC flags, and then we handle the other non-Windows platforms specifically
-  # below.
+  # System-specific flags. If your compiler flags apply to one of the
+  # categories here, add it to the associated file to keep this shared config
+  # smaller.
   if (is_win) {
-    # Windows compiler flags setup.
-    # -----------------------------
-    cflags += [
-      "/Gy",  # Enable function-level linking.
-      "/GS",  # Enable buffer security checking.
-      "/FS",  # Preserve previous PDB behavior.
-      "/bigobj",  # Some of our files are bigger than the regular limits.
-    ]
-
-    if (visual_studio_version == "2015") {
-      # Work around crbug.com/526851, bug in VS 2015 RTM compiler.
-      cflags += [ "/Zc:sizedDealloc-" ]
-    }
-
-    # Force C/C++ mode for the given GN detected file type. This is necessary
-    # for precompiled headers where the same source file is compiled in both
-    # modes.
-    cflags_c += [ "/TC" ]
-    cflags_cc += [ "/TP" ]
-
-    # Building with Clang on Windows is a work in progress and very
-    # experimental. See crbug.com/82385.
-    # Keep this in sync with the similar block in build/common.gypi
-    if (is_clang) {
-      cflags += [
-        # Many files use intrinsics without including this header.
-        # TODO(hans): Fix those files, or move this to sub-GYPs.
-        "/FIIntrin.h",
-      ]
-
-      if (visual_studio_version == "2013") {
-        cflags += [ "-fmsc-version=1800" ]
-      } else if (visual_studio_version == "2015") {
-        cflags += [ "-fmsc-version=1900" ]
-      }
-
-      if (current_cpu == "x86") {
-        cflags += [ "-m32" ]
-      } else {
-        cflags += [ "-m64" ]
-      }
-
-      if (exec_script("//build/win/use_ansi_codes.py", [], "trim string") ==
-          "True") {
-        cflags += [
-          # cmd.exe doesn't understand ANSI escape codes by default,
-          # so only enable them if something emulating them is around.
-          "-fansi-escape-codes",
-        ]
-      }
-    }
+    configs += [ "//build/config/win:compiler" ]
+  } else if (is_android) {
+    configs += [ "//build/config/android:compiler" ]
+  }
 
-    if (is_syzyasan) {
-      # SyzyAsan needs /PROFILE turned on to produce appropriate pdbs.
-      assert(!is_win_fastlink, "/PROFILE and /DEBUG:FASTLINK are incompatible")
-      ldflags += [ "/PROFILE" ]
-    }
-  } else {
+  # In general, Windows is totally different, but all the other builds share
+  # some common GCC configuration.
+  if (!is_win) {
     # Common GCC compiler flags setup.
     # --------------------------------
     cflags += [ "-fno-strict-aliasing" ]  # See http://crbug.com/32204
@@ -601,12 +550,6 @@ config("compiler") {
     cflags_cc += [ "-std=c++11" ]
   }
 
-  # Android-specific flags setup.
-  # -----------------------------
-  if (is_android) {
-    configs += [ "//build/config/android:compiler" ]
-  }
-
   # Pass the same C/C++ flags to the objective C/C++ compiler.
   cflags_objc += cflags_c
   cflags_objcc += cflags_cc
@@ -629,117 +572,20 @@ config("compiler_arm_fpu") {
 # target wants the option regardless, put it in the compiler config.
 
 config("runtime_library") {
-  cflags = []
   defines = []
-  ldflags = []
-  lib_dirs = []
-  libs = []
-
-  if (is_component_build) {
-    # Component mode: dynamic CRT.
-    defines += [ "COMPONENT_BUILD" ]
-    if (is_win) {
-      # Since the library is shared, it requires exceptions or will give errors
-      # about things not matching, so keep exceptions on.
-      if (is_debug) {
-        cflags += [ "/MDd" ]
-      } else {
-        cflags += [ "/MD" ]
-      }
-    }
-  } else {
-    if (is_win && current_os != "win") {
-      # WindowsRT: use the dynamic CRT.
-      if (is_debug) {
-        cflags += [ "/MDd" ]
-      } else {
-        cflags += [ "/MD" ]
-      }
-    } else if (is_win) {
-      # Desktop Windows: static CRT.
-      if (is_debug) {
-        cflags += [ "/MTd" ]
-      } else {
-        cflags += [ "/MT" ]
-      }
-    }
-  }
+  configs = []
 
+  # System-specific flags. If your compiler flags apply to one of the
+  # categories here, add it to the associated file to keep this shared config
+  # smaller.
   if (is_win) {
-    defines += [
-      "__STD_C",
-      "_CRT_RAND_S",
-      "_CRT_SECURE_NO_DEPRECATE",
-      "_HAS_EXCEPTIONS=0",
-      "_SCL_SECURE_NO_DEPRECATE",
-    ]
+    configs += [ "//build/config/win:runtime_library" ]
+  } else if (is_android) {
+    configs += [ "//build/config/android:runtime_library" ]
   }
 
-  # Android standard library setup.
-  if (is_android) {
-    if (is_clang) {
-      # Work around incompatibilities between bionic and clang headers.
-      defines += [
-        "__compiler_offsetof=__builtin_offsetof",
-        "nan=__builtin_nan",
-      ]
-    }
-
-    defines += [ "__GNU_SOURCE=1" ]  # Necessary for clone().
-
-    # TODO(jdduke) Re-enable on mips after resolving linking
-    # issues with libc++ (crbug.com/456380).
-    if (current_cpu != "mipsel" && current_cpu != "mips64el") {
-      ldflags += [ "-Wl,--warn-shared-textrel" ]
-    }
-    ldflags += [ "-nostdlib" ]
-
-    # NOTE: The libc++ header include paths below are specified in cflags
-    # rather than include_dirs because they need to come after include_dirs.
-    # Think of them like system headers, but don't use '-isystem' because the
-    # arm-linux-androideabi-4.4.3 toolchain (circa Gingerbread) will exhibit
-    # strange errors. The include ordering here is important; change with
-    # caution.
-    cflags += [
-      "-isystem" +
-          rebase_path("$android_libcpp_root/libcxx/include", root_build_dir),
-      "-isystem" + rebase_path(
-              "$android_ndk_root/sources/cxx-stl/llvm-libc++abi/libcxxabi/include",
-              root_build_dir),
-      "-isystem" +
-          rebase_path("$android_ndk_root/sources/android/support/include",
-                      root_build_dir),
-    ]
-
-    lib_dirs += [ "$android_libcpp_root/libs/$android_app_abi" ]
-    libs += [ "$android_libcpp_library" ]
-
-    if (current_cpu == "mipsel") {
-      libs += [
-        # ld linker is used for mips Android, and ld does not accept library
-        # absolute path prefixed by "-l"; Since libgcc does not exist in mips
-        # sysroot the proper library will be linked.
-        # TODO(gordanac): Remove once gold linker is used for mips Android.
-        "gcc",
-      ]
-    } else {
-      libs += [
-        # Manually link the libgcc.a that the cross compiler uses. This is
-        # absolute because the linker will look inside the sysroot if it's not.
-        rebase_path(android_libgcc_file),
-      ]
-    }
-
-    libs += [
-      "c",
-      "dl",
-      "m",
-    ]
-
-    # Clang with libc++ does not require an explicit atomic library reference.
-    if (!is_clang) {
-      libs += [ "atomic" ]
-    }
+  if (is_component_build) {
+    defines += [ "COMPONENT_BUILD" ]
   }
 }
 
@@ -1010,6 +856,7 @@ config("chromium_code") {
   cflags += default_warning_flags
   cflags_cc = default_warning_flags_cc
 }
+
 config("no_chromium_code") {
   cflags = []
   cflags_cc = []