commit b03623227ed1264e3cac4e6bb4878d96b91aa484
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Thu Sep 07 11:35:03 2017 -0700
committer Benjamin Peterson <benjamin@python.org> Thu Sep 07 11:35:03 2017 -0700
tree 019511e476f77bf6ed4e2cbfd9c8280ff89d9e96
parent b0d0217c0e4c1512a06ef306928b2fd8f82d046e

[3.6] fixes bpo-31373: fix undefined floating-point demotions (GH-3396) (#3424)

(cherry picked from commit a853a8ba7850381d49b284295dd6f0dc491dbe44)

Objects/floatobject.c

diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 80bf71e..1803a68 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -2182,13 +2182,15 @@
 
     }
     else {
-        float y = (float)x;
-        const unsigned char *s = (unsigned char*)&y;
         int i, incr = 1;
 
-        if (Py_IS_INFINITY(y) && !Py_IS_INFINITY(x))
+        if (fabs(x) > FLT_MAX && !Py_IS_INFINITY(x))
             goto Overflow;
 
+        unsigned char s[sizeof(float)];
+        float y = (float)x;
+        memcpy(s, &y, sizeof(float));
+
         if ((float_format == ieee_little_endian_format && !le)
             || (float_format == ieee_big_endian_format && le)) {
             p += 3;
@@ -2196,7 +2198,7 @@
         }
 
         for (i = 0; i < 4; i++) {
-            *p = *s++;
+            *p = s[i];
             p += incr;
         }
         return 0;