[GN]: Precompiled header support for GCC.

tools/gn/function_toolchain.cc

 // 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.
 
 #include <algorithm>
 #include <limits>
 
 #include "tools/gn/err.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/tool.h"
 #include "tools/gn/toolchain.h"
 #include "tools/gn/value_extractors.h"
 #include "tools/gn/variables.h"
 
 namespace functions {
 
 namespace {
 
-// This is jsut a unique value to take the address of to use as the key for
+// This is just a unique value to take the address of to use as the key for
 // the toolchain property on a scope.
 const int kToolchainPropertyKey = 0;
 
 bool ReadBool(Scope* scope,
               const char* var,
               Tool* tool,
               void (Tool::*set)(bool),
               Err* err) {
   const Value* v = scope->GetValue(var, true);
   if (!v)
@@ skipping 83 matching lines @@
 bool ReadPrecompiledHeaderType(Scope* scope, Tool* tool, Err* err) {
   const Value* value = scope->GetValue("precompiled_header_type", true);
   if (!value)
     return true;  // Not present is fine.
   if (!value->VerifyTypeIs(Value::STRING, err))
     return false;
 
   if (value->string_value().empty())
     return true;  // Accept empty string, do nothing (default is "no PCH").
 
-  if (value->string_value() == "msvc") {
+  if (value->string_value() == "gcc") {
+    tool->set_precompiled_header_type(Tool::PCH_GCC);
+    return true;
+  } else if (value->string_value() == "msvc") {
     tool->set_precompiled_header_type(Tool::PCH_MSVC);
     return true;
   }
   *err = Err(*value, "Invalid precompiled_header_type",
-             "Must either be empty or \"msvc\".");
+             "Must either be empty, \"gcc\", or \"msvc\".");
   return false;
 }
 
 bool ReadDepsFormat(Scope* scope, Tool* tool, Err* err) {
   const Value* value = scope->GetValue("depsformat", true);
   if (!value)
     return true;  // Not present is fine.
   if (!value->VerifyTypeIs(Value::STRING, err))
     return false;
 
@@ skipping 381 matching lines @@
     "\n"
     "        This is typically used to prepend \"lib\" to libraries on\n"
     "        Posix systems:\n"
     "          output_prefix = \"lib\"\n"
     "\n"
     "    precompiled_header_type  [string]\n"
     "        Valid for: \"cc\", \"cxx\", \"objc\", \"objcxx\"\n"
     "\n"
     "        Type of precompiled headers. If undefined or the empty string,\n"
     "        precompiled headers will not be used for this tool. Otherwise\n"
-    "        use \"msvc\" which is the only currently supported value.\n"
+    "        use \"gcc\" or \"msvc\".\n"
     "\n"
     "        For precompiled headers to be used for a given target, the\n"
     "        target (or a config applied to it) must also specify a\n"
     "        \"precompiled_header\" and, for \"msvc\"-style headers, a\n"
-    "        \"precompiled_source\" value.\n"
+    "        \"precompiled_source\" value. If the type is \"gcc\", then both\n"
+    "        \"precompiled_header\" and \"precompiled_source\" must resolve\n"
+    "        to the same file, despite the different formats required for each."
     "\n"
     "        See \"gn help precompiled_header\" for more.\n"
     "\n"
     "    restat  [boolean]\n"
     "        Valid for: all tools (optional, defaults to false)\n"
     "\n"
     "        Requests that Ninja check the file timestamp after this tool has\n"
     "        run to determine if anything changed. Set this if your tool has\n"
     "        the ability to skip writing output if the output file has not\n"
     "        changed.\n"
@@ skipping 399 matching lines @@
     return Value();
 
   Scope::KeyValueMap values;
   block_scope.GetCurrentScopeValues(&values);
   toolchain->args() = values;
 
   return Value();
 }
 
 }  // namespace functions