(_AC_PROG_CC_STDC): Extend test program to get an

error from OSF 4.0 Compaq cc in its default almost-ANSI mode, thereby
ensuring we add -std1 for full-ANSI.

diff --git a/lib/autoconf/c.m4 b/lib/autoconf/c.m4
index 248bc644b3ecaafce089e7dacb49d758b9ee06c0..a560562bf7f0f5fa213ec938b5feed645d2c2593 100644 (file)
--- a/lib/autoconf/c.m4
+++ b/lib/autoconf/c.m4
@@ -805,6 +805,16 @@ static char *f (char * (*g) (char **, int), char **p, ...)
   va_end (v);
   return s;
 }
+
+/* OSF 4.0 Compaq cc is some sort of almost-ANSI by default.  It has
+   function prototypes and stuff, but not '\xHH' hex character constants.
+   These don't provoke an error unfortunately, instead are silently treated
+   as 'x'.  The following induces an error, until -std1 is added to get
+   proper ANSI mode.  Curiously '\x00'!='x' always comes out true, for an
+   array size at least.  It's necessary to write '\x00'==0 to get something
+   that's true only with -std1.  */
+int osf4_cc_array ['\x00' == 0 ? 1 : -1];
+
 int test (int i, double x);
 struct s1 {int (*f) (int a);};
 struct s2 {int (*f) (double a);};