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# pread.m4 serial 8
dnl Copyright (C) 2009-2023 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_PREAD],
[
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
dnl Persuade glibc <unistd.h> to declare pread().
AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
gl_CHECK_FUNCS_ANDROID([pread], [[#include <unistd.h>]])
if test $ac_cv_func_pread = yes; then
dnl On HP-UX 11.11 with _FILE_OFFSET_BITS=64, pread() on a file returns 0
dnl instead of a positive value.
dnl On HP-UX 11.31, pread() on a pipe does not fail.
AC_CACHE_CHECK([whether pread works],
[gl_cv_func_pread_works],
[
dnl Initial guess, used when cross-compiling.
changequote(,)dnl
case "$host_os" in
# Guess no on HP-UX.
hpux*) gl_cv_func_pread_works="guessing no" ;;
# Guess yes otherwise.
*) gl_cv_func_pread_works="guessing yes" ;;
esac
changequote([,])dnl
gl_save_CPPFLAGS="$CPPFLAGS"
CPPFLAGS="$CPPFLAGS -D_FILE_OFFSET_BITS=64"
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([[
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
]GL_MDA_DEFINES],
[[
{
int result = 0;
/* This test fails on HP-UX 11.00..11.11. */
{
int fd = open ("conftest.c", O_RDONLY);
if (fd < 0)
result |= 1;
else
{
char byte_buf;
if (pread (fd, &byte_buf, 1, (off_t) 0) != 1)
result |= 2;
close (fd);
}
}
/* This test fails on HP-UX 11.00..11.31. */
{
FILE *fp = popen ("echo", "r");
if (fp == NULL)
result |= 1;
else
{
int fd = fileno (fp);
char byte_buf;
if (pread (fd, &byte_buf, 1, (off_t) 0) >= 0)
result |= 4;
pclose (fp);
}
}
return result;
}]])],
[gl_cv_func_pread_works=yes],
[gl_cv_func_pread_works=no],
[:])
CPPFLAGS="$gl_save_CPPFLAGS"
])
case "$gl_cv_func_pread_works" in
*yes) ;;
*) REPLACE_PREAD=1 ;;
esac
else
HAVE_PREAD=0
case "$gl_cv_onwards_func_pread" in
future*) REPLACE_PREAD=1 ;;
esac
fi
])
|
