> > Any objections to the following? > > + * m4/btowc.m4 (gl_FUNC_BTOWC): Add a timeout. > > + * doc/posix-functions/btowc.texi (btowc): Document the problem.
Here is a proposed change to m4/wchar.m4 that diagnoses the problem before the btowc test program is even compiled. 2009-12-22 Bruno Haible <[email protected]> wchar: Diagnose broken combination of glibc and gcc versions and flags. * m4/wchar.m4 (gl_WCHAR_H_INLINE_OK): New macro. (gl_WCHAR_H): Invoke it. * m4/btowc.m4 (gl_FUNC_BTOWC): Require it. * doc/posix-headers/wchar.texi: Mention the interoperability problem. --- m4/wchar.m4.orig Tue Dec 22 22:41:53 2009 +++ m4/wchar.m4 Tue Dec 22 22:41:13 2009 @@ -7,7 +7,7 @@ dnl Written by Eric Blake. -# wchar.m4 serial 26 +# wchar.m4 serial 27 AC_DEFUN([gl_WCHAR_H], [ @@ -34,6 +34,8 @@ WCHAR_H=wchar.h fi + gl_WCHAR_H_INLINE_OK + dnl Prepare for creating substitute <wchar.h>. dnl Do it always: WCHAR_H may be empty here but can be set later. dnl Check for <wchar.h> (missing in Linux uClibc when built without wide @@ -50,6 +52,53 @@ gl_CHECK_NEXT_HEADERS([wchar.h]) ]) +dnl Check whether <wchar.h> is usable at all. +AC_DEFUN([gl_WCHAR_H_INLINE_OK], +[ + dnl Test whether <wchar.h> suffers due to the transition from '__inline' to + dnl 'gnu_inline'. See <http://sourceware.org/bugzilla/show_bug.cgi?id=4022> + dnl and <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42440>. In summary, + dnl glibc version 2.5 or older, together with gcc version 4.3 or newer and + dnl the option -std=c99 or -std=gnu99, leads to a broken <wchar.h>. + AC_CACHE_CHECK([whether <wchar.h> uses 'inline' correctly], + [gl_cv_header_wchar_h_correct_inline], + [gl_cv_header_wchar_h_correct_inline=yes + AC_LANG_CONFTEST([ + AC_LANG_SOURCE([[#define wcstod renamed_wcstod +#include <wchar.h> +extern int zero (void); +int main () { return zero(); } +]])]) + if AC_TRY_EVAL([ac_compile]); then + mv conftest.$ac_objext conftest1.$ac_objext + AC_LANG_CONFTEST([ + AC_LANG_SOURCE([[#define wcstod renamed_wcstod +#include <wchar.h> +int zero (void) { return 0; } +]])]) + if AC_TRY_EVAL([ac_compile]); then + mv conftest.$ac_objext conftest2.$ac_objext + if $CC -o conftest$ac_exeext $CFLAGS $LDFLAGS conftest1.$ac_objext conftest2.$ac_objext $LIBS >&AS_MESSAGE_LOG_FD 2>&1; then + : + else + gl_cv_header_wchar_h_correct_inline=no + fi + fi + fi + rm -f conftest1.$ac_objext conftest2.$ac_objext conftest$ac_exeext + ]) + if test $gl_cv_header_wchar_h_correct_inline = no; then + AC_MSG_ERROR([<wchar.h> cannot be used with this compiler ($CC $CFLAGS). +This is a known interoperability problem of glibc <= 2.5 with gcc >= 4.3 in +C99 mode. You have three options: + - Fix your include files, using parts of + <http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=b037a293a48718af30d706c2e18c929d0e69a621>, or + - Use a gcc version older than 4.3, or + - Don't use the flags -std=c99 or -std=gnu99. +Configuration aborted.]) + fi +]) + dnl Unconditionally enables the replacement of <wchar.h>. AC_DEFUN([gl_REPLACE_WCHAR_H], [ --- m4/btowc.m4.orig Tue Dec 22 22:41:53 2009 +++ m4/btowc.m4 Tue Dec 22 22:31:13 2009 @@ -1,4 +1,4 @@ -# btowc.m4 serial 4 +# btowc.m4 serial 5 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, @@ -8,6 +8,11 @@ [ AC_REQUIRE([gl_WCHAR_H_DEFAULTS]) + dnl Check whether <wchar.h> is usable at all, first. Otherwise the test + dnl program below may lead to an endless loop. See + dnl <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42440>. + AC_REQUIRE([gl_WCHAR_H_INLINE_OK]) + AC_CHECK_FUNCS_ONCE([btowc]) if test $ac_cv_func_btowc = no; then HAVE_BTOWC=0 --- doc/posix-headers/wchar.texi.orig Tue Dec 22 22:41:53 2009 +++ doc/posix-headers/wchar.texi Tue Dec 22 22:37:50 2009 @@ -25,4 +25,9 @@ Portability problems not fixed by Gnulib: @itemize +...@item +This header file leads to link errors and endless recursions or endless loops +on some platforms: +glibc version 2.5 or older, together with gcc version 4.3 or newer and the +option @samp{-std=c99} or @samp{-std=gnu99}. @end itemize
