maint: avoid "magic number exit".

* cfg.mk (local-checks-to-skip): No longer skip it.
	* bootstrap.conf (gnulib_modules): Add sysexits.
	* doc/bison.texinfo, etc/bench.pl.in, src/parse-gram.y,
	* src/system.h, tests/calc.at, tests/named-refs.at: Use assert
	where appropriate instead of "if (...) exit".
	Use symbolic exit status elsewhere.

bootstrap.conf

@@ -24,6 +24,7 @@ gnulib_modules='
   javaexec-script ldexpl maintainer-makefile malloc-gnu mbschr mbsrchr
   mbswidth obstack perror pipe-posix quote quotearg realloc-posix
   spawn-pipe stdbool stpcpy strdup-posix strerror strtoul strverscmp
+  sysexits
   unistd unistd-safer unlocked-io update-copyright unsetenv verify
   warnings xalloc xalloc-die xstrndup
 

cfg.mk

@@ -43,7 +43,6 @@ local-checks-to-skip =			\
   sc_prohibit_atoi_atof			\
   sc_prohibit_doubled_word		\
   sc_prohibit_empty_lines_at_EOF	\
-  sc_prohibit_magic_number_exit		\
   sc_prohibit_strcmp
 
 # The local directory containing the checked-out copy of gnulib used in

doc/bison.texinfo

@@ -9969,7 +9969,7 @@ calcxx_driver::scan_begin ()
   else if (!(yyin = fopen (file.c_str (), "r")))
     @{
       error (std::string ("cannot open ") + file + ": " + strerror(errno));
-      exit (1);
+      exit (EXIT_FAILURE);
     @}
 @}
 
@@ -10703,11 +10703,17 @@ yyparse (char const *file)
 {
   yyin = fopen (file, "r");
   if (!yyin)
-    exit (2);
+  {
+    perror ("fopen");
+    exit (EXIT_FAILURE);
+  }
   /* One token only.  */
   yylex ();
   if (fclose (yyin) != 0)
-    exit (3);
+  {
+    perror ("fclose");
+    exit (EXIT_FAILURE);
+  }
   return 0;
 }
 

etc/bench.pl.in

@@ -528,9 +528,8 @@ yylex (void)
 static int
 power (int base, int exponent)
 {
+  assert (0 <= exponent);
   int res = 1;
-  if (exponent < 0)
-    exit (3);
   for (/* Niente */; exponent; --exponent)
     res *= base;
   return res;

lib/.gitignore

@@ -263,3 +263,4 @@
 /closeout.h
 /fpending.c
 /fpending.h
+/sysexits.in.h

m4/.gitignore

@@ -167,3 +167,4 @@
 /xalloc.m4
 /xsize.m4
 /xstrndup.m4
+/sysexits.m4

src/parse-gram.y

@@ -804,7 +804,7 @@ version_check (location const *loc, char const *version)
     {
       complain_at (*loc, "require bison %s, but have %s",
                    version, PACKAGE_VERSION);
-      exit (63);
+      exit (EX_CONFIG);
     }
 }
 

src/system.h

@@ -52,6 +52,7 @@
 typedef size_t uintptr_t;
 #endif
 
+#include <sysexits.h>
 
 /*---------.
 | Gnulib.  |

tests/calc.at

@@ -346,8 +346,7 @@ static int
 power (int base, int exponent)
 {
   int res = 1;
-  if (exponent < 0)
+  assert (0 <= exponent);
-    exit (3);
   for (/* Niente */; exponent; --exponent)
     res *= base;
   return res;

tests/named-refs.at

@@ -15,6 +15,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# FIXME: Duplication with calc.at.
 AT_BANNER([[Named references tests.]])
 
 AT_SETUP([Tutorial calculator])
@@ -142,8 +143,7 @@ int yylex (void)
 static int power (int base, int exponent)
 {
   int res = 1;
-  if (exponent < 0)
+  assert (0 <= exponent);
-    exit (3);
   for (/* Niente */; exponent; --exponent)
     res *= base;
   return res;