commit 5542236837c5c41435f8282ec92799f480c36f18
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Tue Jul 21 22:50:29 2015 -0700

    Port the 0x7efe...feff pattern to GCC 6.
    
    See Steve Ellcey's bug report in:
    https://sourceware.org/ml/libc-alpha/2015-07/msg00673.html
    * string/memrchr.c (MEMRCHR):
    * string/rawmemchr.c (RAWMEMCHR):
    * string/strchr.c (strchr):
    * string/strchrnul.c (STRCHRNUL):
    Rewrite code to avoid issues with signed shift overflow.

---
 string/memrchr.c   |   11 ++---------
 string/rawmemchr.c |   11 ++---------
 string/strchr.c    |    9 ++-------
 string/strchrnul.c |    9 ++-------
 4 files changed, 8 insertions(+), 32 deletions(-)

--- a/string/memrchr.c
+++ b/string/memrchr.c
@@ -96,15 +96,8 @@
 
      The 1-bits make sure that carries propagate to the next 0-bit.
      The 0-bits provide holes for carries to fall into.  */
-
-  if (sizeof (longword) != 4 && sizeof (longword) != 8)
-    abort ();
-
-#if LONG_MAX <= LONG_MAX_32_BITS
-  magic_bits = 0x7efefeff;
-#else
-  magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
-#endif
+  magic_bits = -1;
+  magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
 
   /* Set up a longword, each of whose bytes is C.  */
   charmask = c | (c << 8);
--- a/string/rawmemchr.c
+++ b/string/rawmemchr.c
@@ -86,15 +86,8 @@
 
      The 1-bits make sure that carries propagate to the next 0-bit.
      The 0-bits provide holes for carries to fall into.  */
-
-  if (sizeof (longword) != 4 && sizeof (longword) != 8)
-    abort ();
-
-#if LONG_MAX <= LONG_MAX_32_BITS
-  magic_bits = 0x7efefeff;
-#else
-  magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
-#endif
+  magic_bits = -1;
+  magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
 
   /* Set up a longword, each of whose bytes is C.  */
   charmask = c | (c << 8);
--- a/string/strchr.c
+++ b/string/strchr.c
@@ -63,13 +63,8 @@
 
      The 1-bits make sure that carries propagate to the next 0-bit.
      The 0-bits provide holes for carries to fall into.  */
-  switch (sizeof (longword))
-    {
-    case 4: magic_bits = 0x7efefeffL; break;
-    case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break;
-    default:
-      abort ();
-    }
+  magic_bits = -1;
+  magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
 
   /* Set up a longword, each of whose bytes is C.  */
   charmask = c | (c << 8);
--- a/string/strchrnul.c
+++ b/string/strchrnul.c
@@ -66,13 +66,8 @@
 
      The 1-bits make sure that carries propagate to the next 0-bit.
      The 0-bits provide holes for carries to fall into.  */
-  switch (sizeof (longword))
-    {
-    case 4: magic_bits = 0x7efefeffL; break;
-    case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break;
-    default:
-      abort ();
-    }
+  magic_bits = -1;
+  magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
 
   /* Set up a longword, each of whose bytes is C.  */
   charmask = c | (c << 8);
