strchrnul: work around cygwin bug

A misplaced * means that cygwin 1.7.9 dereferences NULL rather
than returning the location of the trailing NUL byte.

* doc/glibc-functions/strchrnul.texi (strchrnul): Document bug.
* m4/strchrnul.m4 (gl_FUNC_STRCHRNUL): Detect it.
* m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): New witness.
* modules/string (Makefile.am): Substitute it.
* lib/string.in.h (strchrnul): Use it.

Signed-off-by: Eric Blake <eblake@redhat.com>

6 files changed, 64 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 580cfa34e3..5a70916e23 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2011-04-15  Eric Blake  <eblake@redhat.com>
+
+	strchrnul: work around cygwin bug
+	* doc/glibc-functions/strchrnul.texi (strchrnul): Document bug.
+	* m4/strchrnul.m4 (gl_FUNC_STRCHRNUL): Detect it.
+	* m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): New witness.
+	* modules/string (Makefile.am): Substitute it.
+	* lib/string.in.h (strchrnul): Use it.
+
 2011-04-15  Bruno Haible  <bruno@clisp.org>
 
 	Don't require lib/stdio-write.c when only module 'stdio' is used.
diff --git a/doc/glibc-functions/strchrnul.texi b/doc/glibc-functions/strchrnul.texi
index fcb461ea8a..610e935cdc 100644
--- a/doc/glibc-functions/strchrnul.texi
+++ b/doc/glibc-functions/strchrnul.texi
@@ -7,8 +7,13 @@ Gnulib module: strchrnul
 Portability problems fixed by Gnulib:
 @itemize
 @item
-This function is missing on all non-glibc platforms:
-MacOS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS.
+This function is missing on many non-glibc platforms:
+MacOS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11,
+IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.7.8, mingw, Interix 3.5,
+BeOS.
+@item
+This function is broken on some platforms:
+Cygwin 1.7.9.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/string.in.h b/lib/string.in.h
index 652c9407bc..7f156aa453 100644
--- a/lib/string.in.h
+++ b/lib/string.in.h
@@ -277,17 +277,29 @@ _GL_WARN_ON_USE (strchr, "strchr cannot work correctly on character strings "
 
 /* Find the first occurrence of C in S or the final NUL byte.  */
 #if @GNULIB_STRCHRNUL@
-# if ! @HAVE_STRCHRNUL@
+# if @REPLACE_STRCHRNUL@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   define strchrnul rpl_strchrnul
+#  endif
+_GL_FUNCDECL_RPL (strchrnul, char *,
+                  (const char *str, int ch)
+                  _GL_ATTRIBUTE_PURE
+                  _GL_ARG_NONNULL ((1)));
+_GL_CXXALIAS_RPL (strchrnul, char *,
+                  (const char *str, int ch));
+# else
+#  if ! @HAVE_STRCHRNUL@
 _GL_FUNCDECL_SYS (strchrnul, char *, (char const *__s, int __c_in)
                                      _GL_ATTRIBUTE_PURE
                                      _GL_ARG_NONNULL ((1)));
-# endif
+#  endif
   /* On some systems, this function is defined as an overloaded function:
        extern "C++" { const char * std::strchrnul (const char *, int); }
        extern "C++" { char * std::strchrnul (char *, int); }  */
 _GL_CXXALIAS_SYS_CAST2 (strchrnul,
                         char *, (char const *__s, int __c_in),
                         char const *, (char const *__s, int __c_in));
+# endif
 # if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 10) && !defined __UCLIBC__) \
      && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4))
 _GL_CXXALIASWARN1 (strchrnul, char *, (char *__s, int __c_in));
diff --git a/m4/strchrnul.m4 b/m4/strchrnul.m4
index a64e805bd4..52e50a121f 100644
--- a/m4/strchrnul.m4
+++ b/m4/strchrnul.m4
@@ -1,4 +1,4 @@
-# strchrnul.m4 serial 7
+# strchrnul.m4 serial 8
 dnl Copyright (C) 2003, 2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -14,6 +14,36 @@ AC_DEFUN([gl_FUNC_STRCHRNUL],
   if test $ac_cv_func_strchrnul = no; then
     HAVE_STRCHRNUL=0
     gl_PREREQ_STRCHRNUL
+  else
+    AC_CACHE_CHECK([whether strchrnul works],
+      [gl_cv_func_strchrnul_works],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <string.h> /* for strchrnul */
+]], [[const char *buf = "a";
+      return strchrnul(buf, 'b') != buf + 1;
+    ]])],
+        [gl_cv_func_strchrnul_works=yes],
+        [gl_cv_func_strchrnul_works=no],
+        [dnl Cygwin 1.7.9 introduced strchrnul, but it was broken until 1.7.10
+         AC_EGREP_CPP([Lucky user],
+           [
+#if defined __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 9)
+  Lucky user
+ #endif
+#else
+  Lucky user
+#endif
+           ],
+           [gl_cv_func_strchrnul_works=yes],
+           [gl_cv_func_strchrnul_works="guessing no"])
+        ])
+      ])
+    if test "$gl_cv_func_strchrnul_works" != yes; then
+      REPLACE_STRCHRNUL=1
+      AC_LIBOBJ([strchrnul])
+    fi
   fi
 ])
 
diff --git a/m4/string_h.m4 b/m4/string_h.m4
index 30ddfbc3a4..df8c40353b 100644
--- a/m4/string_h.m4
+++ b/m4/string_h.m4
@@ -5,7 +5,7 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# serial 19
+# serial 20
 
 # Written by Paul Eggert.
 
@@ -104,6 +104,7 @@ AC_DEFUN([gl_HEADER_STRING_H_DEFAULTS],
   REPLACE_STRDUP=0;             AC_SUBST([REPLACE_STRDUP])
   REPLACE_STRSTR=0;             AC_SUBST([REPLACE_STRSTR])
   REPLACE_STRCASESTR=0;         AC_SUBST([REPLACE_STRCASESTR])
+  REPLACE_STRCHRNUL=0;          AC_SUBST([REPLACE_STRCHRNUL])
   REPLACE_STRERROR=0;           AC_SUBST([REPLACE_STRERROR])
   REPLACE_STRERROR_R=0;         AC_SUBST([REPLACE_STRERROR_R])
   REPLACE_STRNCAT=0;            AC_SUBST([REPLACE_STRNCAT])
diff --git a/modules/string b/modules/string
index 9b3e9f0fb8..a88bdce00a 100644
--- a/modules/string
+++ b/modules/string
@@ -87,6 +87,7 @@ string.h: string.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H
 	      -e 's|@''REPLACE_MEMCHR''@|$(REPLACE_MEMCHR)|g' \
 	      -e 's|@''REPLACE_MEMMEM''@|$(REPLACE_MEMMEM)|g' \
 	      -e 's|@''REPLACE_STRCASESTR''@|$(REPLACE_STRCASESTR)|g' \
+	      -e 's|@''REPLACE_STRCHRNUL''@|$(REPLACE_STRCHRNUL)|g' \
 	      -e 's|@''REPLACE_STRDUP''@|$(REPLACE_STRDUP)|g' \
 	      -e 's|@''REPLACE_STRSTR''@|$(REPLACE_STRSTR)|g' \
 	      -e 's|@''REPLACE_STRERROR''@|$(REPLACE_STRERROR)|g' \