>From c27ea3054d37a38c64f339e30044b1f463b9affe Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Thu, 5 Oct 2017 17:59:07 -0700
Subject: [PATCH 2/3] Do not malloc more than PTRDIFF_MAX

* src/alloc.c (lmalloc, lrealloc): Do not allocate objects
containing more than PTRDIFF_MAX bytes, as they would
cause pointer subtraction to stop working.  Much of
Emacs already checks for this; this change closes a
couple of loopholes.
---
 src/alloc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/alloc.c b/src/alloc.c
index 2e6399e7f8..ed482c88f2 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1440,6 +1440,12 @@ laligned (void *p, size_t size)
 static void *
 lmalloc (size_t size)
 {
+  if (PTRDIFF_MAX < size)
+    {
+      errno = ENOMEM;
+      return NULL;
+    }
+
 #if USE_ALIGNED_ALLOC
   if (! MALLOC_IS_GC_ALIGNED && size % GCALIGNMENT == 0)
     return aligned_alloc (GCALIGNMENT, size);
@@ -1460,6 +1466,12 @@ lmalloc (size_t size)
 static void *
 lrealloc (void *p, size_t size)
 {
+  if (PTRDIFF_MAX < size)
+    {
+      errno = ENOMEM;
+      return NULL;
+    }
+
   while (true)
     {
       p = realloc (p, size);
-- 
2.13.6