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dup2: work around a Linux bug.

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This commit is contained in:
Bruno Haible
2009-08-25 10:52:51 +02:00
parent 52dec75be7
commit eeee74f5ef
4 changed files with 39 additions and 6 deletions
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8
ChangeLog
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@@ -1,3 +1,11 @@
2009-08-25 Bruno Haible <bruno@clisp.org>
dup2: work around a Linux bug.
* m4/dup2.m4 (gl_FUNC_DUP2): Test for the Linux bug.
* lib/dup2.c (rpl_dup2): Correct the return value if it is -EBADF.
* doc/posix-functions/dup2.texi: Mention the Linux bug.
Reported by Simon Josefsson.
2009-08-25 Jim Meyering <meyering@redhat.com>
libguestfs uses gnulib

6
doc/posix-functions/dup2.texi
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@@ -17,9 +17,13 @@ This function can hang when duplicating an fd to itself on some platforms:
mingw.
@item
This function returns 0 for dup2 (1, 1) on some platforms:
This function returns 0 for @code(dup2 (1, 1)} on some platforms:
Cygwin 1.5.x.
@item
This function may return @code{-EBADF} instead of @code{-1} on some platforms:
Linux releases between July 2008 and May 2009.
@item
This function is missing on some older platforms.
@end itemize

10
lib/dup2.c
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@@ -55,6 +55,16 @@ rpl_dup2 (int fd, int desired_fd)
}
# endif
result = dup2 (fd, desired_fd);
# ifdef __linux__
/* Correct a Linux return value.
<http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.30.y.git;a=commitdiff;h=2b79bc4f7ebbd5af3c8b867968f9f15602d5f802>
*/
if (fd == desired_fd && result == (unsigned int) -EBADF)
{
errno = EBADF;
result = -1;
}
# endif
if (result == 0)
result = desired_fd;
/* Correct a cygwin 1.5.x errno value. */

21
m4/dup2.m4
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@@ -1,4 +1,4 @@
#serial 6
#serial 7
dnl Copyright (C) 2002, 2005, 2007, 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,
@@ -14,17 +14,28 @@ AC_DEFUN([gl_FUNC_DUP2],
AC_LIBOBJ([dup2])
else
AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <unistd.h>
]], [return 1 - dup2 (1, 1);])],
[AC_RUN_IFELSE([
AC_LANG_PROGRAM([[#include <unistd.h>]],
[if (dup2 (1, 1) == 0)
return 1;
close (0);
if (dup2 (0, 0) != -1)
return 1;
return 0;
])
],
[gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
[case "$host_os" in
mingw*) # on this platform, dup2 always returns 0 for success
gl_cv_func_dup2_works=no;;
cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
gl_cv_func_dup2_works=no;;
linux*) # On linux between 2008-07-27 and 2009-05-11, dup2 of a
# closed fd may yield -EBADF instead of -1 / errno=EBADF.
gl_cv_func_dup2_works=no;;
*) gl_cv_func_dup2_works=yes;;
esac])])
esac])
])
if test "$gl_cv_func_dup2_works" = no; then
REPLACE_DUP2=1
AC_LIBOBJ([dup2])