--- a/gcc/c-family/c-opts.c	Fri Oct 27 22:46:09 2017 +0900
+++ b/gcc/c-family/c-opts.c	Thu Oct 25 07:37:49 2018 +0900
@@ -1,5 +1,5 @@
 /* C/ObjC/C++ command line option handling.
-   Copyright (C) 2002-2017 Free Software Foundation, Inc.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
    Contributed by Neil Booth.
 
 This file is part of GCC.
@@ -40,6 +40,7 @@
 #include "plugin.h"		/* For PLUGIN_INCLUDE_FILE event.  */
 #include "mkdeps.h"
 #include "dumpfile.h"
+#include "file-prefix-map.h"    /* add_*_prefix_map()  */
 
 #ifndef DOLLARS_IN_IDENTIFIERS
 # define DOLLARS_IN_IDENTIFIERS true
@@ -115,6 +116,8 @@
 static void set_std_c89 (int, int);
 static void set_std_c99 (int);
 static void set_std_c11 (int);
+static void set_std_c17 (int);
+static void set_std_c2x (int);
 static void check_deps_environment_vars (void);
 static void handle_deferred_opts (void);
 static void sanitize_cpp_opts (void);
@@ -222,7 +225,7 @@
   parse_in = cpp_create_reader (c_dialect_cxx () ? CLK_GNUCXX: CLK_GNUC89,
 				ident_hash, line_table);
   cb = cpp_get_callbacks (parse_in);
-  cb->error = c_cpp_error;
+  cb->diagnostic = c_cpp_diagnostic;
 
   cpp_opts = cpp_get_options (parse_in);
   cpp_opts->dollars_in_ident = DOLLARS_IN_IDENTIFIERS;
@@ -236,8 +239,8 @@
 
   if (c_language == clk_c)
     {
-      /* The default for C is gnu11.  */
-      set_std_c11 (false /* ISO */);
+      /* The default for C is gnu17.  */
+      set_std_c17 (false /* ISO */);
 
       /* If preprocessing assembly language, accept any of the C-family
 	 front end options since the driver may pass them through.  */
@@ -260,7 +263,7 @@
    form of an -f or -W option was given.  Returns false if the switch was
    invalid, true if valid.  Use HANDLERS in recursive handle_option calls.  */
 bool
-c_common_handle_option (size_t scode, const char *arg, int value,
+c_common_handle_option (size_t scode, const char *arg, HOST_WIDE_INT value,
 			int kind, location_t loc,
 			const struct cl_option_handlers *handlers)
 {
@@ -379,16 +382,6 @@
       cpp_opts->warn_num_sign_change = value;
       break;
 
-    case OPT_Walloca_larger_than_:
-      if (!value)
-	inform (loc, "-Walloca-larger-than=0 is meaningless");
-      break;
-
-    case OPT_Wvla_larger_than_:
-      if (!value)
-	inform (loc, "-Wvla-larger-than=0 is meaningless");
-      break;
-
     case OPT_Wunknown_pragmas:
       /* Set to greater than 1, so that even unknown pragmas in
 	 system headers will be warned about.  */
@@ -415,8 +408,6 @@
 	  value = 2;
 	}
       warn_abi_version = value;
-      if (flag_abi_compat_version == -1)
-	flag_abi_compat_version = value;
       break;
 
     case OPT_fcanonical_system_headers:
@@ -447,6 +438,10 @@
       cpp_opts->dollars_in_ident = value;
       break;
 
+    case OPT_fmacro_prefix_map_:
+      add_macro_prefix_map (arg);
+      break;
+
     case OPT_ffreestanding:
       value = !value;
       /* Fall through.  */
@@ -675,6 +670,26 @@
 	set_std_c11 (false /* ISO */);
       break;
 
+    case OPT_std_c17:
+      if (!preprocessing_asm_p)
+	set_std_c17 (true /* ISO */);
+      break;
+
+    case OPT_std_gnu17:
+      if (!preprocessing_asm_p)
+	set_std_c17 (false /* ISO */);
+      break;
+
+    case OPT_std_c2x:
+      if (!preprocessing_asm_p)
+	set_std_c2x (true /* ISO */);
+      break;
+
+    case OPT_std_gnu2x:
+      if (!preprocessing_asm_p)
+	set_std_c2x (false /* ISO */);
+      break;
+
     case OPT_trigraphs:
       cpp_opts->trigraphs = 1;
       break;
@@ -899,31 +914,49 @@
   if (flag_declone_ctor_dtor == -1)
     flag_declone_ctor_dtor = optimize_size;
 
-  if (warn_abi_version == -1)
-    {
-      if (flag_abi_compat_version != -1)
-	warn_abi_version = flag_abi_compat_version;
-      else
-	warn_abi_version = 0;
-    }
-
   if (flag_abi_compat_version == 1)
     {
       warning (0, "%<-fabi-compat-version=1%> is not supported, using =2");
       flag_abi_compat_version = 2;
     }
-  else if (flag_abi_compat_version == -1)
+
+  /* Change flag_abi_version to be the actual current ABI level, for the
+     benefit of c_cpp_builtins, and to make comparison simpler.  */
+  const int latest_abi_version = 13;
+  /* Generate compatibility aliases for ABI v11 (7.1) by default.  */
+  const int abi_compat_default = 11;
+
+#define clamp(X) if (X == 0 || X > latest_abi_version) X = latest_abi_version
+  clamp (flag_abi_version);
+  clamp (warn_abi_version);
+  clamp (flag_abi_compat_version);
+#undef clamp
+
+  /* Default -Wabi= or -fabi-compat-version= from each other.  */
+  if (warn_abi_version == -1 && flag_abi_compat_version != -1)
+    warn_abi_version = flag_abi_compat_version;
+  else if (flag_abi_compat_version == -1 && warn_abi_version != -1)
+    flag_abi_compat_version = warn_abi_version;
+  else if (warn_abi_version == -1 && flag_abi_compat_version == -1)
     {
-      /* Generate compatibility aliases for ABI v11 (7.1) by default. */
-      flag_abi_compat_version
-	= (flag_abi_version == 0 ? 11 : 0);
+      warn_abi_version = latest_abi_version;
+      if (flag_abi_version == latest_abi_version)
+	{
+	  auto_diagnostic_group d;
+	  if (warning (OPT_Wabi, "-Wabi won't warn about anything"))
+	    {
+	      inform (input_location, "-Wabi warns about differences "
+		      "from the most up-to-date ABI, which is also used "
+		      "by default");
+	      inform (input_location, "use e.g. -Wabi=11 to warn about "
+		      "changes from GCC 7");
+	    }
+	  flag_abi_compat_version = abi_compat_default;
+	}
+      else
+	flag_abi_compat_version = latest_abi_version;
     }
 
-  /* Change flag_abi_version to be the actual current ABI level for the
-     benefit of c_cpp_builtins.  */
-  if (flag_abi_version == 0)
-    flag_abi_version = 12;
-
   /* By default, enable the new inheriting constructor semantics along with ABI
      11.  New and old should coexist fine, but it is a change in what
      artificial symbols are generated.  */
@@ -978,6 +1011,10 @@
 	flag_extern_tls_init = 1;
     }
 
+  /* Enable by default only for C++ and C++ with ObjC extensions.  */
+  if (warn_return_type == -1 && c_dialect_cxx ())
+    warn_return_type = 1;
+
   if (num_in_fnames > 1)
     error ("too many filenames given.  Type %s --help for usage",
 	   progname);
@@ -1528,6 +1565,7 @@
   flag_isoc94 = c94;
   flag_isoc99 = 0;
   flag_isoc11 = 0;
+  flag_isoc2x = 0;
   lang_hooks.name = "GNU C89";
 }
 
@@ -1539,6 +1577,7 @@
   flag_no_asm = iso;
   flag_no_nonansi_builtin = iso;
   flag_iso = iso;
+  flag_isoc2x = 0;
   flag_isoc11 = 0;
   flag_isoc99 = 1;
   flag_isoc94 = 1;
@@ -1553,12 +1592,44 @@
   flag_no_asm = iso;
   flag_no_nonansi_builtin = iso;
   flag_iso = iso;
+  flag_isoc2x = 0;
   flag_isoc11 = 1;
   flag_isoc99 = 1;
   flag_isoc94 = 1;
   lang_hooks.name = "GNU C11";
 }
 
+/* Set the C 17 standard (without GNU extensions if ISO).  */
+static void
+set_std_c17 (int iso)
+{
+  cpp_set_lang (parse_in, iso ? CLK_STDC17: CLK_GNUC17);
+  flag_no_asm = iso;
+  flag_no_nonansi_builtin = iso;
+  flag_iso = iso;
+  flag_isoc2x = 0;
+  flag_isoc11 = 1;
+  flag_isoc99 = 1;
+  flag_isoc94 = 1;
+  lang_hooks.name = "GNU C17";
+}
+
+/* Set the C 2X standard (without GNU extensions if ISO).  */
+static void
+set_std_c2x (int iso)
+{
+  cpp_set_lang (parse_in, iso ? CLK_STDC2X: CLK_GNUC2X);
+  flag_no_asm = iso;
+  flag_no_nonansi_builtin = iso;
+  flag_iso = iso;
+  flag_isoc2x = 1;
+  flag_isoc11 = 1;
+  flag_isoc99 = 1;
+  flag_isoc94 = 1;
+  lang_hooks.name = "GNU C2X";
+}
+
+
 /* Set the C++ 98 standard (without GNU extensions if ISO).  */
 static void
 set_std_cxx98 (int iso)