SIGFPE and x86

[Eric Blake]

I'm checking this in; yet another case of a missing port from branch-1_4 (fixed 
6 months ago in 1.4.5, no less).

2007-04-03  Eric Blake  <address@hidden>

        * modules/m4.c (numb_ratio, numb_divide, numb_modulo): Avoid
        SIGFPE on x86 architectures.
        Reported by Ralf Wildenhues.

Index: modules/m4.c
===================================================================
RCS file: /sources/m4/m4/modules/m4.c,v
retrieving revision 1.105
diff -u -r1.105 m4.c
--- modules/m4.c        2 Apr 2007 12:06:23 -0000       1.105
+++ modules/m4.c        3 Apr 2007 21:01:00 -0000
@@ -1095,9 +1095,13 @@
 #define numb_negate(x)   ((x) = (- (x)))
 
 #define numb_times(x, y)     ((x) = ((x) * (y)))
-#define numb_ratio(x, y)     ((x) = ((x) / ((y))))
-#define numb_divide(x, y)    (*(x) = (*(x) / (*(y))))
-#define numb_modulo(c, x, y) (*(x) = (*(x) % *(y)))
+/* Be careful of x86 SIGFPE.  */
+#define numb_ratio(x, y)                                               \
+  (((y) == -1) ? (numb_negate (x)) : ((x) /= (y)))
+#define numb_divide(x, y)                                              \
+  ((*(y) == -1) ? (numb_negate (*(y))) : (*(x) /= *(y)))
+#define numb_modulo(c, x, y)                                           \
+  ((*(y) == -1) ? (*(x) = numb_ZERO) : (*(x) %= *(y)))
 /* numb_invert is only used in the context of x**-y, which integral math
    does not support.  */
 #define numb_invert(x)       return NEGATIVE_EXPONENT