skeletons: update the handling of compiler attributes

* data/c.m4 (b4_attribute_define): Instead of defining __attribute__,
define YY_ATTRIBUTE conditionally.
(YY_ATTRIBUTE_PURE, YY_ATTRIBUTE_UNUSED, _Noreturn): New.
Use them.
* data/glr.c: Use them.

2 files changed, 33 insertions, 19 deletions

diff --git a/data/c.m4 b/data/c.m4
index b1b43948..9b739bc4 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -205,13 +205,32 @@ m4_define([b4_table_value_equals],
 
 # b4_attribute_define
 # -------------------
-# Provide portability for __attribute__.
+# Provide portable compiler "attributes".
 m4_define([b4_attribute_define],
-[#ifndef __attribute__
-/* This feature is available in gcc versions 2.5 and later.  */
-# if (! defined __GNUC__ || __GNUC__ < 2 \
-      || (__GNUC__ == 2 && __GNUC_MINOR__ < 5))
-#  define __attribute__(Spec) /* empty */
+[#ifndef YY_ATTRIBUTE
+# if (defined __GNUC__                                               \
+      && (2 < __GNUC__ || (__GNUC__ == 2 && 96 <= __GNUC_MINOR__)))  \
+     || defined __SUNPRO_C && 0x5110 <= __SUNPRO_C
+#  define YY_ATTRIBUTE(Spec) __attribute__(Spec)
+# else
+#  define YY_ATTRIBUTE(Spec) /* empty */
+# endif
+#endif
+
+#ifndef YY_ATTRIBUTE_PURE
+# define YY_ATTRIBUTE_PURE   YY_ATTRIBUTE ((__pure__))
+#endif
+
+#ifndef YY_ATTRIBUTE_UNUSED
+# define YY_ATTRIBUTE_UNUSED YY_ATTRIBUTE ((__unused__))
+#endif
+
+#if !defined _Noreturn \
+     && (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112)
+# if defined _MSC_VER && 1200 <= _MSC_VER
+#  define _Noreturn __declspec (noreturn)
+# else
+#  define _Noreturn YY_ATTRIBUTE ((__noreturn__))
 # endif
 #endif
 
@@ -783,7 +802,7 @@ m4_define([b4_yy_location_print_define],
 
 /* Print *YYLOCP on YYO.  Private, do not rely on its existence. */
 
-__attribute__((__unused__))
+YY_ATTRIBUTE_UNUSED
 ]b4_function_define([yy_location_print_],
     [static unsigned],
                [[FILE *yyo],                    [yyo]],
diff --git a/data/glr.c b/data/glr.c
index 8ef35534..725453be 100644
--- a/data/glr.c
+++ b/data/glr.c
@@ -445,9 +445,9 @@ int yydebug;
 
 struct yyGLRStack;
 static void yypstack (struct yyGLRStack* yystackp, size_t yyk)
-  __attribute__ ((__unused__));
+  YY_ATTRIBUTE_UNUSED;
 static void yypdumpstack (struct yyGLRStack* yystackp)
-  __attribute__ ((__unused__));
+  YY_ATTRIBUTE_UNUSED;
 
 #else /* !]b4_api_PREFIX[DEBUG */
 
@@ -669,9 +669,7 @@ struct yyGLRStack {
 static void yyexpandGLRStack (yyGLRStack* yystackp);
 #endif
 
-static void yyFail (yyGLRStack* yystackp]b4_pure_formals[, const char* yymsg)
-  __attribute__ ((__noreturn__));
-static void
+static _Noreturn void
 yyFail (yyGLRStack* yystackp]b4_pure_formals[, const char* yymsg)
 {
   if (yymsg != YY_NULL)
@@ -679,9 +677,7 @@ yyFail (yyGLRStack* yystackp]b4_pure_formals[, const char* yymsg)
   YYLONGJMP (yystackp->yyexception_buffer, 1);
 }
 
-static void yyMemoryExhausted (yyGLRStack* yystackp)
-  __attribute__ ((__noreturn__));
-static void
+static _Noreturn void
 yyMemoryExhausted (yyGLRStack* yystackp)
 {
   YYLONGJMP (yystackp->yyexception_buffer, 2);
@@ -702,7 +698,7 @@ yytokenName (yySymbol yytoken)
 /** Fill in YYVSP[YYLOW1 .. YYLOW0-1] from the chain of states starting
  *  at YYVSP[YYLOW0].yystate.yypred.  Leaves YYVSP[YYLOW1].yystate.yypred
  *  containing the pointer to the next state in the chain.  */
-static void yyfillin (yyGLRStackItem *, int, int) __attribute__ ((__unused__));
+static void yyfillin (yyGLRStackItem *, int, int) YY_ATTRIBUTE_UNUSED;
 static void
 yyfillin (yyGLRStackItem *yyvsp, int yylow0, int yylow1)
 {
@@ -729,7 +725,7 @@ yyfillin (yyGLRStackItem *yyvsp, int yylow0, int yylow1)
  * YYVSP[YYLOW1 .. *YYLOW-1] as in yyfillin and set *YYLOW = YYLOW1.
  * For convenience, always return YYLOW1.  */
 static inline int yyfill (yyGLRStackItem *, int *, int, yybool)
-     __attribute__ ((__unused__));
+     YY_ATTRIBUTE_UNUSED;
 static inline int
 yyfill (yyGLRStackItem *yyvsp, int *yylow, int yylow1, yybool yynormal)
 {
@@ -751,8 +747,7 @@ yyuserAction (yyRuleNum yyn, size_t yyrhslen, yyGLRStackItem* yyvsp,
               yyGLRStack* yystackp,
               YYSTYPE* yyvalp]b4_locuser_formals[)
 {
-  yybool yynormal __attribute__ ((__unused__)) =
-    (yystackp->yysplitPoint == YY_NULL);
+  yybool yynormal YY_ATTRIBUTE_UNUSED = (yystackp->yysplitPoint == YY_NULL);
   int yylow;
 ]b4_parse_param_use([yyvalp], [yylocp])dnl
 [  YYUSE (yyrhslen);