Mercurial > gnulib
view m4/dup2.m4 @ 37189:82ff83d5d4a7
dup2, dup3: work around another cygwin crasher
Cygwin 1.7.25 can crash due to an off-by-one bug on an attempt to
duplicate a file into the current RLIMIT_NOFILE soft limit, when
that limit is smaller than the hard limit. The intent in the
cygwin code was to allow the dup and auto-increase the soft limit,
which is itself questionable (and which we work around in the
gnulib getdtablesize module); but avoiding the crash is worth
doing even if the soft limit semantics are wrong.
http://cygwin.com/ml/cygwin/2013-09/msg00397.html
http://cygwin.com/ml/cygwin-developers/2013-q3/msg00010.html
* m4/dup2.m4 (gl_FUNC_DUP2): Expose the bug.
* m4/dup3.m4 (gl_FUNC_DUP3): Likewise.
* tests/test-dup2.c (main): Likewise.
* lib/dup2.c (rpl_dup2): Use setdtablesize to avoid it.
* lib/dup3.c (dup3): Likewise.
* doc/posix-functions/dup2.texi (dup2): Document it.
* doc/glibc-functions/dup3.texi (dup3): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
author | Eric Blake <eblake@redhat.com> |
---|---|
date | Thu, 26 Sep 2013 07:07:07 -0600 |
parents | c741bc27922a |
children | 344018b6e5d7 |
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#serial 20 dnl Copyright (C) 2002, 2005, 2007, 2009-2013 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_DUP2], [ AC_REQUIRE([gl_UNISTD_H_DEFAULTS]) AC_REQUIRE([AC_CANONICAL_HOST]) m4_ifdef([gl_FUNC_DUP2_OBSOLETE], [ AC_CHECK_FUNCS_ONCE([dup2]) if test $ac_cv_func_dup2 = no; then HAVE_DUP2=0 fi ], [ AC_DEFINE([HAVE_DUP2], [1], [Define to 1 if you have the 'dup2' function.]) ]) if test $HAVE_DUP2 = 1; then AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works], [AC_RUN_IFELSE([ AC_LANG_PROGRAM([[#include <unistd.h> #include <fcntl.h> #include <errno.h>]], [int result = 0; #ifdef FD_CLOEXEC if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1) result |= 1; #endif if (dup2 (1, 1) == 0) result |= 2; #ifdef FD_CLOEXEC if (fcntl (1, F_GETFD) != FD_CLOEXEC) result |= 4; #endif close (0); if (dup2 (0, 0) != -1) result |= 8; /* Many gnulib modules require POSIX conformance of EBADF. */ if (dup2 (2, 1000000) == -1 && errno != EBADF) result |= 16; /* Flush out some cygwin core dumps. */ if (dup2 (2, -1) != -1 || errno != EBADF) result |= 32; dup2 (2, 255); dup2 (2, 256); return result; ]) ], [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no], [case "$host_os" in mingw*) # on this platform, dup2 always returns 0 for success gl_cv_func_dup2_works="guessing no" ;; cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0 gl_cv_func_dup2_works="guessing no" ;; linux*) # On linux between 2008-07-27 and 2009-05-11, dup2 of a # closed fd may yield -EBADF instead of -1 / errno=EBADF. gl_cv_func_dup2_works="guessing no" ;; freebsd*) # on FreeBSD 6.1, dup2(1,1000000) gives EMFILE, not EBADF. gl_cv_func_dup2_works="guessing no" ;; haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC. gl_cv_func_dup2_works="guessing no" ;; *) gl_cv_func_dup2_works="guessing yes" ;; esac]) ]) case "$gl_cv_func_dup2_works" in *yes) ;; *) REPLACE_DUP2=1 AC_CHECK_FUNCS([setdtablesize]) ;; esac fi dnl Replace dup2() for supporting the gnulib-defined fchdir() function, dnl to keep fchdir's bookkeeping up-to-date. m4_ifdef([gl_FUNC_FCHDIR], [ gl_TEST_FCHDIR if test $HAVE_FCHDIR = 0; then if test $HAVE_DUP2 = 1; then REPLACE_DUP2=1 fi fi ]) ]) # Prerequisites of lib/dup2.c. AC_DEFUN([gl_PREREQ_DUP2], [])