From fc5290458d00e3eebf82dd914fd2848b7e3f7e87 Mon Sep 17 00:00:00 2001
From: Mark Dickinson <dickinsm@gmail.com>
Date: Sat, 23 Jan 2010 20:48:56 +0000
Subject: Issue #7743:  Add checks for zero inputs to the lshift and mult
 functions; this fixes the first bug described in issue #7743.

---
 Python/dtoa.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Python/dtoa.c b/Python/dtoa.c
index 6e11b9a..6a93aef 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -622,6 +622,15 @@ mult(Bigint *a, Bigint *b)
     ULong z2;
 #endif
 
+    if ((!a->x[0] && a->wds == 1) || (!b->x[0] && b->wds == 1)) {
+        c = Balloc(0);
+        if (c == NULL)
+            return NULL;
+        c->wds = 1;
+        c->x[0] = 0;
+        return c;
+    }
+
     if (a->wds < b->wds) {
         c = a;
         a = b;
@@ -820,6 +829,9 @@ lshift(Bigint *b, int k)
     Bigint *b1;
     ULong *x, *x1, *xe, z;
 
+    if (!k || (!b->x[0] && b->wds == 1))
+        return b;
+
     n = k >> 5;
     k1 = b->k;
     n1 = n + b->wds + 1;
-- 
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