>From 34b6b3c88d3c25562641ca9ed107ba93f08158b0 Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Sun, 21 Aug 2016 23:22:35 -0700
Subject: [PATCH] grep: minor tweaks of initial buffer alloc

* src/grep.c (main): Allocate input buffer only when about
to do I/O.  Avoid int overflow on systems with 2 GiB pages.
Fix size_t overflow check.
---
 src/grep.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/grep.c b/src/grep.c
index 63487d6..0c84b2a 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -2320,12 +2320,6 @@ main (int argc, char **argv)
   set_program_name (argv[0]);
   program_name = argv[0];
 
-  pagesize = getpagesize ();
-  if (pagesize == 0 || 2 * pagesize + 1 <= pagesize)
-    abort ();
-  bufalloc = (ALIGN_TO (INITIAL_BUFSIZE, pagesize) + pagesize + sizeof (uword));
-  buffer = xmalloc (bufalloc);
-
   keys = NULL;
   keycc = 0;
   with_filenames = false;
@@ -2777,6 +2771,18 @@ main (int argc, char **argv)
   if (max_count == 0)
     return EXIT_FAILURE;
 
+  /* Prefer sysconf for page size, as getpagesize typically returns int.  */
+#ifdef _SC_PAGESIZE
+  long psize = sysconf (_SC_PAGESIZE);
+#else
+  long psize = getpagesize ();
+#endif
+  if (! (0 < psize && psize <= (SIZE_MAX - sizeof (uword)) / 2))
+    abort ();
+  pagesize = psize;
+  bufalloc = ALIGN_TO (INITIAL_BUFSIZE, pagesize) + pagesize + sizeof (uword);
+  buffer = xmalloc (bufalloc);
+
   if (fts_options & FTS_LOGICAL && devices == READ_COMMAND_LINE_DEVICES)
     devices = READ_DEVICES;
 
-- 
2.5.5