[PATCH 12/12] yacc.c: portability to G++ 4.8

[Akim Demaille]

Currently we get warnings with GCC 4.8 when running the
maintainer-check-g++ tests:

    143. skeletons.at:85: testing Installed skeleton file names ...
    ../../tests/skeletons.at:120: COLUMNS=1000; export COLUMNS;  bison 
--color=no -fno-caret --skeleton=yacc.c -o input-cmd-line.c input-cmd-line.y
    ../../tests/skeletons.at:121: $CC $CFLAGS $CPPFLAGS  $LDFLAGS -o 
input-cmd-line input-cmd-line.c $LIBS
    stderr:
    input-cmd-line.c: In function 'int yysyntax_error(long int*, char**, const 
yyparse_context_t*)':
    input-cmd-line.c:977:52: error: conversion to 'int' from 'long int' may 
alter its value [-Werror=conversion]
                                       YYSIZEOF (yyarg) / YYSIZEOF (*yyarg));
                                                        ^
    cc1plus: all warnings being treated as errors
    stdout:
    ../../tests/skeletons.at:121: exit code was 1, expected 0

and

    429. calc.at:823: testing Calculator parse.error=custom %locations 
api.prefix={calc}  ...
    ../../tests/calc.at:823: COLUMNS=1000; export COLUMNS;  bison --color=no 
-fno-caret -Wno-deprecated -o calc.c calc.y
    ../../tests/calc.at:823: $CC $CFLAGS $CPPFLAGS  $LDFLAGS -o calc calc.c 
$LIBS
    stderr:
    calc.y: In function 'int yyreport_syntax_error(const yyparse_context_t*)':
    calc.y:157:58: error: conversion to 'int' from 'long unsigned int' may 
alter its value [-Werror=conversion]
       int n = yysyntax_error_arguments (ctx, arg, sizeof arg / sizeof *arg);
                                                              ^
    cc1plus: all warnings being treated as errors
    stdout:
    ../../tests/calc.at:823: exit code was 1, expected 0

We could use a cast to avoid the warning, but it becomes too
cluttered.  We can also use YYPTRDIFF_T, but that forces the user to
use YYPTRDIFF_T too, although this is an array of tokens, which is
limited by YYNTOKENS, an int.  So let's completely avoid this warning.

* data/skeletons/yacc.c, tests/local.at (yyreport_syntax_error): Avoid
relying on sizeof to compute the array capacity.
---
 data/skeletons/yacc.c | 24 +++++++++---------------
 tests/local.at        |  2 +-
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/data/skeletons/yacc.c b/data/skeletons/yacc.c
index f3353b4a..a73d119c 100644
--- a/data/skeletons/yacc.c
+++ b/data/skeletons/yacc.c
@@ -1057,10 +1057,10 @@ yy_lac (yy_state_t *yyesa, yy_state_t **yyes,
   YYPTRDIFF_T *yyes_capacity_p;]])[
 } yyparse_context_t;
 
-/* Put in YYARG at most YYARGN of the expected tokens given
-   the current YYCTX, and return the number of tokens stored
-   in YYARG.
-   If YYARG is null, return the number of expected tokens.  */
+/* Put in YYARG at most YYARGN of the expected tokens given the
+   current YYCTX, and return the number of tokens stored in YYARG.  If
+   YYARG is null, return the number of expected tokens (guaranteed to
+   be less than YYNTOKENS).  */
 static int
 yyexpected_tokens (const yyparse_context_t *yyctx,
                    int yyarg[], int yyargn)
@@ -1286,20 +1286,14 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
   /* Arguments of yyformat: reported tokens (one for the "unexpected",
      one per "expected"). */
   int yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
-  /* Actual size of YYARG. */
-  int yycount = 0;
   /* Cumulated lengths of YYARG.  */
   YYPTRDIFF_T yysize = 0;
 
-  {
-    int yyn
-      = yysyntax_error_arguments (yyctx, yyarg,
-                                  YYSIZEOF (yyarg) / YYSIZEOF (*yyarg));
-    if (yyn == -2)
-      return 2;
-    else
-      yycount = yyn;
-  }
+  /* Actual size of YYARG. */
+  int yycount
+    = yysyntax_error_arguments (yyctx, yyarg, YYERROR_VERBOSE_ARGS_MAXIMUM);
+  if (yycount == -2)
+    return 2;
 
   switch (yycount)
     {
diff --git a/tests/local.at b/tests/local.at
index 30062a2e..ee5beddf 100644
--- a/tests/local.at
+++ b/tests/local.at
@@ -615,7 +615,7 @@ yyreport_syntax_error (const yyparse_context_t 
*ctx]AT_PARAM_IF([, AT_PARSE_PARA
   /* Arguments of yyformat: reported tokens (one for the "unexpected",
      one per "expected"). */
   int arg[YYNTOKENS];
-  int n = yysyntax_error_arguments (ctx, arg, sizeof arg / sizeof 
*arg);]AT_PARAM_IF([m4_bpatsubst(m4_defn([AT_PARSE_PARAMS]),
+  int n = yysyntax_error_arguments (ctx, arg, 
YYNTOKENS);]AT_PARAM_IF([m4_bpatsubst(m4_defn([AT_PARSE_PARAMS]),
               [[^,]+[^A-Za-z_0-9]\([A-Za-z_][A-Za-z_0-9]*\),* *], [
   YYUSE (\1);])])[]m4_bmatch(m4_defn([AT_PARSE_PARAMS]), [nerrs],[[
   ++global_nerrs;
-- 
2.24.1