PATCH: prevent SIGFPE on systems where LONG_MIN < -LONG_MAX

["Jérémie Roquet" <arkanosis@gmail.com>]

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Hello,

$ echo $[ - 2**63 / -1 ]
zsh: floating point exception  ./Src/zsh

$ echo $[ - 2**63 % -1 ]
zsh: floating point exception  ./Src/zsh

The attached patch fixes this.

Best regards,

-- 
Jérémie

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diff --git a/Src/math.c b/Src/math.c
index cca5210..5e0a509 100644
--- a/Src/math.c
+++ b/Src/math.c
@@ -32,6 +32,7 @@ struct mathvalue;
 #include "zsh.mdh"
 #include "math.pro"
 
+#include <limits.h>
 #include <math.h>
 
 /* nonzero means we are not evaluating, just parsing */
@@ -962,6 +963,19 @@ notzero(mnumber a)
     return 1;
 }
 
+/**/
+static int
+representable(mnumber a, mnumber b)
+{
+#if LONG_MIN < -LONG_MAX
+    if (a.u.l - 1 > a.u.l && b.u.l == -1) {
+	zerr("non representable result");
+	return 0;
+    }
+#endif
+    return 1;
+}
+
 /* macro to pop three values off the value stack */
 
 /**/
@@ -1053,13 +1067,18 @@ op(int what)
 		    return;
 		if (c.type == MN_FLOAT)
 		    c.u.d = a.u.d / b.u.d;
-		else
+		else {
+                    if (!representable(a, b))
+                        return;
 		    c.u.l = a.u.l / b.u.l;
+                }
 		break;
 	    case MOD:
 	    case MODEQ:
 		if (!notzero(b))
 		    return;
+                if (!representable(a, b))
+                    return;
 		c.u.l = a.u.l % b.u.l;
 		break;
 	    case PLUS: