Changes to m4/modules/m4.c,v

[Eric Blake]

CVSROOT:        /sources/m4
Module name:    m4
Changes by:     Eric Blake <ericb>      07/05/24 20:13:44

Index: modules/m4.c
===================================================================
RCS file: /sources/m4/m4/modules/m4.c,v
retrieving revision 1.108
retrieving revision 1.109
diff -u -b -r1.108 -r1.109
--- modules/m4.c        24 May 2007 18:02:54 -0000      1.108
+++ modules/m4.c        24 May 2007 20:13:44 -0000      1.109
@@ -100,14 +100,8 @@
   BUILTIN (undivert,   false,  false,  false,  0,      -1 )    \
 
 
-#if defined(SIZEOF_LONG_LONG_INT) && SIZEOF_LONG_LONG_INT > 0
-/* Use GNU long long int if available.  */
-typedef long long int number;
-typedef unsigned long long int unumber;
-#else
-typedef long int number;
-typedef unsigned long int unumber;
-#endif
+typedef intmax_t number;
+typedef uintmax_t unumber;
 
 static void    include         (m4 *context, int argc, m4_symbol_value **argv,
                                 bool silent);
@@ -1103,10 +1097,21 @@
    does not support.  */
 #define numb_invert(x)       return NEGATIVE_EXPONENT
 
-#define numb_lshift(c, x, y)  (*(x) = (*(x) << *(y)))
-#define numb_rshift(c, x, y)  (*(x) = (*(x) >> *(y)))
+/* Minimize undefined C behavior (shifting by a negative number,
+   shifting by the width or greater, left shift overflow, or right
+   shift of a negative number).  Implement Java wrap-around semantics,
+   with implicit masking of shift amount.  This code assumes that the
+   implementation-defined overflow when casting unsigned to signed is
+   a silent twos-complement wrap-around.  */
+#define shift_mask (sizeof (number) * CHAR_BIT - 1)
+#define numb_lshift(c, x, y)                                   \
+  (*(x) = (number) ((unumber) *(x) << (*(y) & shift_mask)))
+#define numb_rshift(c, x, y)                                   \
+  (*(x) = (number) (*(x) < 0                                   \
+                   ? ~(~(unumber) *(x) >> (*(y) & shift_mask)) \
+                   : (unumber) *(x) >> (*(y) & shift_mask)))
 #define numb_urshift(c, x, y)                          \
-   (*(x) = (number) ((unumber) *(x) >> (unumber) *(y)))
+  (*(x) = (number) ((unumber) *(x) >> (*(y) & shift_mask)))
 
 
 /* The function ntoa () converts VALUE to a signed ascii representation in