Re: test-memchr crash

[Eric Blake]

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According to Simon Josefsson on 6/16/2009 1:30 AM:
> checking whether strstr works in linear time... no
> ...
> PASS: test-strstr
> 
> I checked, and the gnulib strstr replacement is used.

Oh.  That's because your strstr is already non-linear (your glibc 2.7 is
older than when they picked up my strstr implementation, around Feb 2008
and glibc 2.9).  So there's only a narrow window of time where glibc has
the new strstr that uses memchr with an overestimated length, but also has
a broken memchr, and we have not yet run into a host in the wild in that
category other than the Debian bug report.

All that said, I think I will still commit this patch, unless anyone objects:

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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>From a099937a4efb3208abd6db29d63706439ed42c4f Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Tue, 16 Jun 2009 06:14:05 -0600
Subject: [PATCH] strstr: replace on platforms with broken memchr

* m4/strstr.m4 (gl_FUNC_STRSTR): Also replace strstr if the
platform version is linear but memchr is broken, per Debian bug
521737.
* doc/posix-functions/strstr.texi (strstr): Document the fix.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog                       |    8 ++++++++
 doc/posix-functions/strstr.texi |    7 ++++++-
 m4/strstr.m4                    |    9 ++++++---
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 1a06849..38e62f2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2009-06-16  Eric Blake  <address@hidden>
+
+       strstr: replace on platforms with broken memchr
+       * m4/strstr.m4 (gl_FUNC_STRSTR): Also replace strstr if the
+       platform version is linear but memchr is broken, per Debian bug
+       521737.
+       * doc/posix-functions/strstr.texi (strstr): Document the fix.
+
 2009-06-15  Eric Blake  <address@hidden>

        hash: avoid memory leak on allocation failure
diff --git a/doc/posix-functions/strstr.texi b/doc/posix-functions/strstr.texi
index ffd2ad7..2e58050 100644
--- a/doc/posix-functions/strstr.texi
+++ b/doc/posix-functions/strstr.texi
@@ -11,7 +11,12 @@ Portability problems fixed by Gnulib:
 @item
 This function has quadratic instead of linear worst-case complexity on some
 platforms:
-glibc 2.8, MacOS X 10.3, FreeBSD 6.2, NetBSD 3.0, OpenBSD 4.0, AIX 5.1, HP-UX 
11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw.
+glibc 2.8, MacOS X 10.3, FreeBSD 6.2, NetBSD 3.0, OpenBSD 4.0, AIX
+5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw.
+
address@hidden
+This function can trigger memchr bugs on some platforms:
+glibc 2.10.
 @end itemize

 Portability problems not fixed by Gnulib:
diff --git a/m4/strstr.m4 b/m4/strstr.m4
index f48bebb..9f4819d 100644
--- a/m4/strstr.m4
+++ b/m4/strstr.m4
@@ -1,5 +1,5 @@
-# strstr.m4 serial 5
-dnl Copyright (C) 2008 Free Software Foundation, Inc.
+# strstr.m4 serial 6
+dnl Copyright (C) 2008, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -8,6 +8,7 @@ dnl Check that strstr is efficient.
 AC_DEFUN([gl_FUNC_STRSTR],
 [
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MEMCHR])
   AC_CACHE_CHECK([whether strstr works in linear time],
     [gl_cv_func_strstr_linear],
     [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
@@ -57,7 +58,9 @@ AC_DEFUN([gl_FUNC_STRSTR],
         [gl_cv_func_strstr_linear="guessing no"])
       ])
     ])
-  if test "$gl_cv_func_strstr_linear" != yes; then
+  # If strstr is quadratic, or if memchr is broken (as in glibc 2.10 on
+  # some 64-bit architectures), then we need the replacement.
+  if test "$gl_cv_func_strstr_linear$gl_cv_func_memchr_works" != yesyes; then
     REPLACE_STRSTR=1
     AC_LIBOBJ([strstr])
   fi
-- 
1.6.3.rc3.2.g4b51