gn: various flag matching for 'base'

build/config/BUILDCONFIG.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.
 
 # =============================================================================
 # BUILD FLAGS
 # =============================================================================
 #
 # This block lists input arguments to the build, along with their default
 # values. GN requires listing them explicitly so it can validate input and have
 # a central place to manage the build flags.
 #
 # If a value is specified on the command line, it will overwrite the defaults
 # given here, otherwise the default will be injected into the root scope.
 #
 # KEEP IN ALPHABETICAL ORDER and write a good description for everything.
 # Use "is_*" names for intrinsic platform descriptions and build modes, and
 # "use_*" names for optional features libraries, and configurations.
 declare_args() {
   # How many symbols to include in the build. This affects the performance of
   # the build since the symbols are large and dealing with them is slow.
   #   2 means regular build with symbols.
   #   1 means minimal symbols, usually enough for backtraces only.
   #   0 means no symbols.
-  symbol_level = 2
+  #   -1 means auto-set (off in release, regular in debug).
+  symbol_level = -1
 
   # Component build.
   is_component_build = false
   # Debug build.
   is_debug = true
 
   # Set to true when compiling with the Clang compiler. Typically this is used
   # to configure warnings.
   is_clang = (os == "mac" || os == "ios" || os == "linux")
 
@@ skipping 311 matching lines @@
 # Optimizations and debug checking.
 if (is_debug) {
   _native_compiler_configs += [ "//build/config:debug" ]
   _default_optimization_config = "//build/config/compiler:no_optimize"
 } else {
   _native_compiler_configs += [ "//build/config:release" ]
   _default_optimization_config = "//build/config/compiler:optimize"
 }
 _native_compiler_configs += [ _default_optimization_config ]
 
+# If it wasn't manually set, set to an appropriate default.
+if (symbol_level == -1) {
+  # Linux is slowed by having symbols as part of the target binary, whereas
+  # Mac and Windows have them separate, so in Release Linux, default them off.
+  if (is_debug || !is_linux) {
+    symbol_level = 2
+  } else {
+    symbol_level = 0
+  }
+}
+
 # Symbol setup.
 if (symbol_level == 2) {
   _default_symbols_config = "//build/config/compiler:symbols"
 } else if (symbol_level == 1) {
   _default_symbols_config = "//build/config/compiler:minimal_symbols"
 } else if (symbol_level == 0) {
   _default_symbols_config = "//build/config/compiler:no_symbols"
 } else {
   assert(false, "Bad value for symbol_level.")
 }
@@ skipping 286 matching lines @@
       if (defined(invoker.lib_dirs)) { lib_dirs = invoker.lib_dirs }
       if (defined(invoker.libs)) { libs = invoker.libs }
       if (defined(invoker.output_extension)) { output_extension = invoker.output_extension }
       if (defined(invoker.output_name)) { output_name = invoker.output_name }
       if (defined(invoker.public)) { public = invoker.public }
       if (defined(invoker.sources)) { sources = invoker.sources }
       if (defined(invoker.visibility)) { visibility = invoker.visibility }
     }
   }
 }