Add -std=c2x, -std=gnu2x, -Wc11-c2x-compat, C2X _Static_assert support.

Now new features are starting to be added to a C2X draft (in the C2x
branch of the C standard git repository, no public WG14 document yet),
it's time to add -std=c2x and associated options to GCC for use in
enabling C2X features.

This patch adds the expected set of options: -std=c2x, -std=gnu2x,
-Wc11-c2x-compat.  A first C2X feature is added (the only one so far
in the repository that's obviously relevant to GCC): support (as in
C++) for the string constant to be omitted in _Static_assert.  This
feature is duly also supported as an extension in earlier standard
modes (diagnosed with -pedantic, unless -Wno-c11-c2x-compat is given,
or with -Wc11-c2x-compat even in C2X mode).

Bootstrapped with no regressions on x86_64-pc-linux-gnu.

gcc/
	* doc/cpp.texi (__STDC_VERSION__): Document C2X handling.
	* doc/invoke.texi (-std=c2x, -std=gnu2x): Document new options.
	* doc/standards.texi (C Language): Document C2X.
	* dwarf2out.c (highest_c_language), config/rl78/rl78.c
	(rl78_option_override): Handle "GNU C2X" language name.

gcc/c/
	* c-errors.c (pedwarn_c11): New function.
	* c-parser.c (disable_extension_diagnostics): Save
	warn_c11_c2x_compat and set it to 0.
	(restore_extension_diagnostics): Restore warn_c11_c2x_compat.
	(c_parser_static_assert_declaration_no_semi): Handle
	_Static_assert without string constant.
	* c-tree.h (pedwarn_c11): New prototype.

gcc/c-family/
	* c-common.c (flag_isoc2x): New variable.
	* c-common.h (clk_c): Update comment to reference C2X.
	(flag_isoc99, flag_isoc11): Update comments to reference future
	standard versions in general.
	(flag_isoc2x): Declare.
	* c-opts.c (set_std_c2x): New function.
	(c_common_handle_option): Handle -std=c2x and -std=gnu2x.
	(set_std_c89, set_std_c99, set_std_c11, set_std_c17): Set
	flag_isoc2x to 0.
	* c.opt (Wc11-c2x-compat, std=c2x, std=gnu2x): New options.

gcc/testsuite/
	* gcc.dg/c11-static-assert-7.c, gcc.dg/c11-static-assert-8.c,
	gcc.dg/c11-static-assert-9.c, gcc.dg/c2x-static-assert-1.c,
	gcc.dg/c2x-static-assert-2.c, gcc.dg/c99-static-assert-2.c,
	gcc.dg/gnu2x-static-assert-1.c: New tests.
	* gcc.dg/missing-symbol-3.c: Update expected fix-it text.

libcpp/
	* include/cpplib.h (enum c_lang): Add CLK_GNUC2X and CLK_STDC2X.
	* init.c (lang_defaults): Add GNUC2X and STDC2X entries.
	(cpp_init_builtins): Define __STDC_VERSION__ to 202000L for C2X.

From-SVN: r265251

3 files changed, 13 insertions, 1 deletions

diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index e240b2c7058..fd08a330cca 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,9 @@
+2018-10-17  Joseph Myers  <joseph@codesourcery.com>
+
+	* include/cpplib.h (enum c_lang): Add CLK_GNUC2X and CLK_STDC2X.
+	* init.c (lang_defaults): Add GNUC2X and STDC2X entries.
+	(cpp_init_builtins): Define __STDC_VERSION__ to 202000L for C2X.
+
 2018-10-11  David Malcolm  <dmalcolm@redhat.com>
 
 	* macro.c (_cpp_arguments_ok): If the argument count is wrong, add
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 797cfb92e78..a9b4fb3973c 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -167,8 +167,9 @@ enum cpp_ttype
 #undef TK
 
 /* C language kind, used when calling cpp_create_reader.  */
-enum c_lang {CLK_GNUC89 = 0, CLK_GNUC99, CLK_GNUC11, CLK_GNUC17,
+enum c_lang {CLK_GNUC89 = 0, CLK_GNUC99, CLK_GNUC11, CLK_GNUC17, CLK_GNUC2X,
 	     CLK_STDC89, CLK_STDC94, CLK_STDC99, CLK_STDC11, CLK_STDC17,
+	     CLK_STDC2X,
 	     CLK_GNUCXX, CLK_CXX98, CLK_GNUCXX11, CLK_CXX11,
 	     CLK_GNUCXX14, CLK_CXX14, CLK_GNUCXX17, CLK_CXX17,
 	     CLK_GNUCXX2A, CLK_CXX2A, CLK_ASM};
diff --git a/libcpp/init.c b/libcpp/init.c
index 32a59565174..9b7490b0d8a 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -100,11 +100,13 @@ static const struct lang_flags lang_defaults[] =
   /* GNUC99   */  { 1,  0,  1,  1,  0,  0,  1,   1,   1,   0,    0,     0,     0,   0,      1 },
   /* GNUC11   */  { 1,  0,  1,  1,  1,  0,  1,   1,   1,   0,    0,     0,     0,   0,      1 },
   /* GNUC17   */  { 1,  0,  1,  1,  1,  0,  1,   1,   1,   0,    0,     0,     0,   0,      1 },
+  /* GNUC2X   */  { 1,  0,  1,  1,  1,  0,  1,   1,   1,   0,    0,     0,     0,   0,      1 },
   /* STDC89   */  { 0,  0,  0,  0,  0,  1,  0,   0,   0,   0,    0,     0,     1,   0,      0 },
   /* STDC94   */  { 0,  0,  0,  0,  0,  1,  1,   0,   0,   0,    0,     0,     1,   0,      0 },
   /* STDC99   */  { 1,  0,  1,  1,  0,  1,  1,   0,   0,   0,    0,     0,     1,   0,      0 },
   /* STDC11   */  { 1,  0,  1,  1,  1,  1,  1,   1,   0,   0,    0,     0,     1,   0,      0 },
   /* STDC17   */  { 1,  0,  1,  1,  1,  1,  1,   1,   0,   0,    0,     0,     1,   0,      0 },
+  /* STDC2X   */  { 1,  0,  1,  1,  1,  1,  1,   1,   0,   0,    0,     0,     1,   0,      0 },
   /* GNUCXX   */  { 0,  1,  1,  1,  0,  0,  1,   0,   0,   0,    0,     0,     0,   0,      1 },
   /* CXX98    */  { 0,  1,  0,  1,  0,  1,  1,   0,   0,   0,    0,     0,     1,   0,      0 },
   /* GNUCXX11 */  { 1,  1,  1,  1,  1,  0,  1,   1,   1,   1,    0,     0,     0,   0,      1 },
@@ -521,6 +523,9 @@ cpp_init_builtins (cpp_reader *pfile, int hosted)
     _cpp_define_builtin (pfile, "__ASSEMBLER__ 1");
   else if (CPP_OPTION (pfile, lang) == CLK_STDC94)
     _cpp_define_builtin (pfile, "__STDC_VERSION__ 199409L");
+  else if (CPP_OPTION (pfile, lang) == CLK_STDC2X
+	   || CPP_OPTION (pfile, lang) == CLK_GNUC2X)
+    _cpp_define_builtin (pfile, "__STDC_VERSION__ 202000L");
   else if (CPP_OPTION (pfile, lang) == CLK_STDC17
 	   || CPP_OPTION (pfile, lang) == CLK_GNUC17)
     _cpp_define_builtin (pfile, "__STDC_VERSION__ 201710L");