Re: Bug in AC_FUNC_MEMCMP when using g++

[Akim Demaille]

| It seems that the testsource for AC_FUNC_MEMCMP in autoconf 2.57 does
| not contain a string.h include which makes the check fail when running
| a C++ compiler (g++ v3.1 in my case). This can be reproduced by using
| the following configure.ac
| ---
| AC_INIT(memcpy_bug, 1.0)
| AC_CHECK_HEADERS
| AC_FUNC_MEMCMP
| ---
| and trying both a './configure' and a './configure CC=g++'.
| The first gives
| ---
| checking for working memcmp... yes
| ---
| while the second gives
| ---
| checking for working memcmp... no
| ---
| 
| An addition of
| ---
| #ifdef HAVE_STRING_H
| #include <string.h>
| #endif
| ---
| to the testsource should fix this problem.
| 
| Regards,
| Sander Niemeijer

Thanks, I'm installing the following patch:

Index: ChangeLog
from  Akim Demaille  <address@hidden>

        * lib/autoconf/functions.m4: Use the default includes so that
        memcmp be declared before being tested.
        Reported by Sander Niemeijer.
        (AC_FUNC_ERROR_AT_LINE, AC_FUNC_GETGROUPS, AC_FUNC_STRNLEN): Likewise.
        * doc/autoconf.texi (Default Includes): Document
        AC_INCLUDES_DEFAULT.

Index: NEWS
===================================================================
RCS file: /cvsroot/autoconf/autoconf/NEWS,v
retrieving revision 1.294
diff -u -u -w -r1.294 NEWS
--- NEWS 17 May 2003 09:44:22 -0000 1.294
+++ NEWS 17 May 2003 10:27:39 -0000
@@ -1,7 +1,7 @@
 * Major changes in Autoconf 2.57a                       -*- outline -*-
 
 ** New macros
-  AC_C_RESTRICT
+  AC_C_RESTRICT, AC_INCLUDES_DEFAULT.
 
 ** AC_DECL_SYS_SIGLIST
   Works again.
Index: THANKS
===================================================================
RCS file: /cvsroot/autoconf/autoconf/THANKS,v
retrieving revision 1.109
diff -u -u -w -r1.109 THANKS
--- THANKS 16 May 2003 09:54:46 -0000 1.109
+++ THANKS 17 May 2003 10:27:40 -0000
@@ -171,6 +171,7 @@
 Russ Allbery                address@hidden
 Ryuji Abe                   address@hidden
 Sam Varshavchik             address@hidden
+Sander Niemeijer            address@hidden
 Scott Bambrough             address@hidden
 Scott Stanton               address@hidden
 Simon Leinen                address@hidden
Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.734
diff -u -u -w -r1.734 autoconf.texi
--- doc/autoconf.texi 17 May 2003 09:44:22 -0000 1.734
+++ doc/autoconf.texi 17 May 2003 10:28:03 -0000
@@ -3077,7 +3077,12 @@
 unconditional includes, and check the existence of the headers you
 include beforehand (@pxref{Header Files}).
 
-Most generic macros provide the following default set of includes:
+Most generic macros use the following macro to provide the default set
+of includes:
+
address@hidden AC_DEFAULT_INCLUDES (@ovar{include-directives})
address@hidden
+Expand to @var{include-directives} if defined, otherwise to:
 
 @example
 @group
@@ -3118,15 +3123,15 @@
 @end group
 @end example
 
-If the default includes are used, then Autoconf will automatically check
-for the presence of these headers and their compatibility, i.e., you
-don't need to run @code{AC_HEADERS_STDC}, nor check for @file{stdlib.h}
-etc.
+If the default includes are used, then check for the presence of these
+headers and their compatibility, i.e., you don't need to run
address@hidden, nor check for @file{stdlib.h} etc.
 
 These headers are checked for in the same order as they are included.
 For instance, on some systems @file{string.h} and @file{strings.h} both
 exist, but conflict.  Then @code{HAVE_STRING_H} will be defined, but
 @code{HAVE_STRINGS_H} won't.
address@hidden defmac
 
 @node Alternative Programs
 @section Alternative Programs
@@ -13253,12 +13258,12 @@
 
 @defmac AC_TEST_CPP
 @acindex{TEST_CPP}
address@hidden, replaced with @code{AC_PREPROC_IFELSE}.
address@hidden, replaced by @code{AC_PREPROC_IFELSE}.
 @end defmac
 
 @defmac AC_TEST_PROGRAM
 @acindex{TEST_PROGRAM}
address@hidden, replaced with @code{AC_RUN_IFELSE}.
address@hidden, replaced by @code{AC_RUN_IFELSE}.
 @end defmac
 
 @defmac AC_TIMEZONE
Index: lib/autoconf/functions.m4
===================================================================
RCS file: /cvsroot/autoconf/autoconf/lib/autoconf/functions.m4,v
retrieving revision 1.75
diff -u -u -w -r1.75 functions.m4
--- lib/autoconf/functions.m4 31 Oct 2002 17:33:26 -0000 1.75
+++ lib/autoconf/functions.m4 17 May 2003 10:28:04 -0000
@@ -1,6 +1,6 @@
 # This file is part of Autoconf.                       -*- Autoconf -*-
 # Checking for functions.
-# Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
+# Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -443,7 +443,8 @@
 AC_DEFUN([AC_FUNC_ERROR_AT_LINE],
 [AC_LIBSOURCES([error.h, error.c])dnl
 AC_CACHE_CHECK([for error_at_line], ac_cv_lib_error_at_line,
-[AC_LINK_IFELSE([AC_LANG_PROGRAM([],[error_at_line (0, 0, "", 0, "");])],
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
+                                [error_at_line (0, 0, "", 0, "");])],
                 [ac_cv_lib_error_at_line=yes],
                 [ac_cv_lib_error_at_line=no])])
 if test $ac_cv_lib_error_at_line = no; then
@@ -597,7 +598,7 @@
 # getgroups function only if there is such a function.
 if test $ac_cv_func_getgroups = yes; then
   AC_CACHE_CHECK([for working getgroups], ac_cv_func_getgroups_works,
-   [AC_RUN_IFELSE([AC_LANG_PROGRAM([],
+   [AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
       [[/* On Ultrix 4.3, getgroups (0, 0) always fails.  */
        exit (getgroups (0, 0) == -1 ? 1 : 0);]])],
                   [ac_cv_func_getgroups_works=yes],
@@ -902,7 +903,7 @@
 AN_FUNCTION([memcmp], [AC_FUNC_MEMCMP])
 AC_DEFUN([AC_FUNC_MEMCMP],
 [AC_CACHE_CHECK([for working memcmp], ac_cv_func_memcmp_working,
-[AC_RUN_IFELSE([AC_LANG_PROGRAM([], [[
+[AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT], [[
   /* Some versions of memcmp are not 8-bit clean.  */
   char c0 = 0x40, c1 = 0x80, c2 = 0x81;
   if (memcmp(&c0, &c2, 1) >= 0 || memcmp(&c1, &c2, 1) >= 0)
@@ -1543,7 +1544,7 @@
 AN_FUNCTION([strnlen], [AC_FUNC_STRNLEN])
 AC_DEFUN([AC_FUNC_STRNLEN],
 [AC_CACHE_CHECK([for working strnlen], ac_cv_func_strnlen_working,
-[AC_RUN_IFELSE([AC_LANG_PROGRAM([], [[
+[AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT], [[
 #define S "foobar"
 #define S_LEN (sizeof S - 1)