2 dnl Copyright (C) 2007, 2009-2012 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 AC_DEFUN([gl_FUNC_LSEEK],
9 AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10 AC_REQUIRE([AC_CANONICAL_HOST])
11 AC_REQUIRE([AC_PROG_CC])
12 AC_CHECK_HEADERS_ONCE([unistd.h])
13 AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],
17 dnl The result of lseek (fd, (off_t)0, SEEK_CUR) or
18 dnl SetFilePointer(handle, 0, NULL, FILE_CURRENT)
19 dnl for a pipe depends on the environment: In a Cygwin 1.5
20 dnl environment it succeeds (wrong); in a Cygwin 1.7 environment
21 dnl it fails with a wrong errno value.
22 gl_cv_func_lseek_pipe=no
25 if test $cross_compiling = no; then
26 AC_LINK_IFELSE([AC_LANG_PROGRAM([[
27 #include <sys/types.h> /* for off_t */
28 #include <stdio.h> /* for SEEK_CUR */
31 #else /* on Windows with MSVC */
35 /* Exit with success only if stdin is seekable. */
36 return lseek (0, (off_t)0, SEEK_CUR) < 0;
38 [if test -s conftest$ac_exeext \
39 && ./conftest$ac_exeext < conftest.$ac_ext \
40 && test 1 = "`echo hi \
41 | { ./conftest$ac_exeext; echo $?; cat >/dev/null; }`"; then
42 gl_cv_func_lseek_pipe=yes
44 gl_cv_func_lseek_pipe=no
47 [gl_cv_func_lseek_pipe=no])
52 /* BeOS mistakenly return 0 when trying to seek on pipes. */
55 [gl_cv_func_lseek_pipe=yes], [gl_cv_func_lseek_pipe=no])
60 if test $gl_cv_func_lseek_pipe = no; then
62 AC_DEFINE([LSEEK_PIPE_BROKEN], [1],
63 [Define to 1 if lseek does not detect pipes.])