--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2009-06-17  Eric Blake  <ebb9@byu.net>
+
+	strstr, strcasestr: replace on platforms with broken memchr
+	* modules/strstr: Split into...
+	* modules/strstr-simple: ...new module that does not care about
+	performance, but does care about glibc bug.
+	* m4/strstr.m4 (gl_FUNC_STRSTR): Split...
+	(gl_FUNC_STRSTR_SIMPLE): ...into new macro, which replaces strstr
+	if platform memchr is broken, per Debian bug 521737.
+	* m4/strcasestr.m4 (gl_FUNC_STRCASESTR_SIMPLE): React to broken
+	memchr.
+	* m4/memchr.m4 (gl_FUNC_MEMCHR): Only expand once.
+	* doc/posix-functions/strstr.texi (strstr): Document the fix.
+	* doc/glibc-functions/strcasestr.texi (strcasestr): Likewise.
+	* modules/mountlist (Depends-on): Add strstr-simple.
+	* modules/gen-uni-tables (Depends-on): Likewise.
+	* modules/argz (Depends-on): Add strstr.
+
 2009-06-17  Bruno Haible  <bruno@clisp.org>
 
 	* modules/posix_spawn-internal (Depends-on): Add errno.

--- a/doc/glibc-functions/strcasestr.texi
+++ b/doc/glibc-functions/strcasestr.texi
@@ -9,7 +9,12 @@
 @itemize
 @item
 This function is missing on some platforms:
-AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw, BeOS.
+AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x,
+mingw, BeOS.
+
+@item
+This function can trigger memchr bugs on some platforms:
+glibc 2.10.
 @end itemize
 
 Portability problems fixed by Gnulib module @code{strcasestr}:

--- a/doc/posix-functions/strstr.texi
+++ b/doc/posix-functions/strstr.texi
@@ -4,14 +4,23 @@
 
 POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/strstr.html}
 
-Gnulib module: strstr
+Gnulib module: strstr or strstr-simple
 
-Portability problems fixed by Gnulib:
+Portability problems fixed by either Gnulib module @code{strstr-simple}
+or @code{strstr}:
+@itemize
+@item
+This function can trigger memchr bugs on some platforms:
+glibc 2.10.
+@end itemize
+
+Portability problems fixed by Gnulib @code{strstr}:
 @itemize
 @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.
 @end itemize
 
 Portability problems not fixed by Gnulib:

--- a/m4/memchr.m4
+++ b/m4/memchr.m4
@@ -1,10 +1,10 @@
-# memchr.m4 serial 6
+# memchr.m4 serial 7
 dnl Copyright (C) 2002, 2003, 2004, 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.
 
-AC_DEFUN([gl_FUNC_MEMCHR],
+AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
 [
   dnl Check for prerequisites for memory fence checks.
   gl_FUNC_MMAP_ANON

--- a/m4/strcasestr.m4
+++ b/m4/strcasestr.m4
@@ -1,20 +1,25 @@
-# strcasestr.m4 serial 12
-dnl Copyright (C) 2005, 2007, 2008 Free Software Foundation, Inc.
+# strcasestr.m4 serial 13
+dnl Copyright (C) 2005, 2007, 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.
 
-dnl Check that strcasestr is present.
+dnl Check that strcasestr is present and works.
 AC_DEFUN([gl_FUNC_STRCASESTR_SIMPLE],
 [
   dnl Persuade glibc <string.h> to declare strcasestr().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MEMCHR])
   AC_REPLACE_FUNCS([strcasestr])
   if test $ac_cv_func_strcasestr = no; then
     HAVE_STRCASESTR=0
     gl_PREREQ_STRCASESTR
+  elif test "$gl_cv_func_memchr_works" != yes; then
+    REPLACE_STRCASESTR=1
+    AC_LIBOBJ([strcasestr])
+    gl_PREREQ_STRCASESTR
   fi
 ]) # gl_FUNC_STRCASESTR_SIMPLE
 

--- a/m4/strstr.m4
+++ b/m4/strstr.m4
@@ -1,13 +1,24 @@
-# 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.
 
-dnl Check that strstr is efficient.
+dnl Check that strstr works.
+AC_DEFUN([gl_FUNC_STRSTR_SIMPLE],
+[
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MEMCHR])
+  if test "$gl_cv_func_memchr_works" != yes; then
+    REPLACE_STRSTR=1
+    AC_LIBOBJ([strstr])
+  fi
+]) # gl_FUNC_STRSTR_SIMPLE
+
+dnl Additionally, check that strstr is efficient.
 AC_DEFUN([gl_FUNC_STRSTR],
 [
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_STRSTR_SIMPLE])
   AC_CACHE_CHECK([whether strstr works in linear time],
     [gl_cv_func_strstr_linear],
     [AC_RUN_IFELSE([AC_LANG_PROGRAM([[

--- a/modules/argz
+++ b/modules/argz
@@ -12,6 +12,7 @@
 stpcpy
 strndup
 strnlen
+strstr
 
 configure.ac:
 gl_FUNC_ARGZ

--- a/modules/gen-uni-tables
+++ b/modules/gen-uni-tables
@@ -10,6 +10,7 @@
 Depends-on:
 memcmp
 strdup
+strstr-simple
 
 configure.ac:
 

--- a/modules/mountlist
+++ b/modules/mountlist
@@ -11,6 +11,7 @@
 Depends-on:
 stdbool
 stdint
+strstr-simple
 xalloc
 
 configure.ac:

--- a/modules/strstr
+++ b/modules/strstr
@@ -2,19 +2,12 @@
 strstr() function: efficiently locate first substring in a buffer.
 
 Files:
-lib/str-two-way.h
-lib/strstr.c
-m4/strstr.m4
 
 Depends-on:
-string
-stdbool
-memchr
-memcmp
+strstr-simple
 
 configure.ac:
 gl_FUNC_STRSTR
-gl_STRING_MODULE_INDICATOR([strstr])
 
 Makefile.am:
 

new file mode 100644
--- /dev/null
+++ b/modules/strstr-simple
@@ -0,0 +1,28 @@
+Description:
+strstr() function: locate first substring in a buffer.
+
+Files:
+lib/str-two-way.h
+lib/strstr.c
+m4/strstr.m4
+
+Depends-on:
+string
+stdbool
+memchr
+memcmp
+
+configure.ac:
+gl_FUNC_STRSTR_SIMPLE
+gl_STRING_MODULE_INDICATOR([strstr])
+
+Makefile.am:
+
+Include:
+<string.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+all, Eric Blake