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dnl @synopsis AX_CHECK_SYSCALL_LSEEK([ACTION-IF-TRUE], [ACTION-IF-FALSE])
dnl
dnl This macro will find out if the lseek syscall requires a dummy middle
dnl parameter
dnl
dnl The following defines will be set as appropriate:
dnl HAVE_LSEEK_DUMMY_PARAM
dnl Also ACTION-IF-TRUE and ACTION-IF-FALSE are run as appropriate
dnl
dnl @category C
dnl @author Martin Ebourne
dnl @version 2005/07/03
dnl @license AllPermissive
dnl
AC_DEFUN(
[AX_TRY_RUN_FD],
[
AC_REQUIRE([AX_FUNC_SYSCALL])dnl
if test "x$ac_cv_header_sys_syscall_h" = "xyes"; then
AC_TRY_RUN(
[
$ac_includes_default
#include <fcntl.h>
#include <sys/syscall.h>
#ifdef HAVE___SYSCALL_NEED_DEFN
extern "C" off_t __syscall(quad_t number, ...);
#endif
#ifdef HAVE___SYSCALL // always use it if we have it
#undef syscall
#define syscall __syscall
#endif
int main()
{
int fd = creat("lseektest", 0600);
int res = 1;
if(fd>=0)
{
$1
close(fd);
}
unlink("lseektest");
return abs(res);
}
],
[$2],
[$3],
[$3 # assume not for cross-compiling]
)
fi
])dnl
AC_DEFUN([AX_CHECK_SYSCALL_LSEEK_DUMMY_PARAM], [
AC_CACHE_CHECK(
[[whether syscall lseek requires dummy parameter]],
[box_cv_have_lseek_dummy_param],
[AX_TRY_RUN_FD(
[
// This test tries first to seek to position 0, with NO
// "dummy argument". If lseek does actually require a dummy
// argument, then it will eat SEEK_SET for the offset and
// try to use 99 as whence, which is invalid, so res will be
// 1, the program will return 1 and we will define
// HAVE_LSEEK_DUMMY_PARAM
// (whew! that took 1 hour to figure out)
// The "dummy argument" probably means that it takes a 64-bit
// offset.
res = (syscall(SYS_lseek, fd, (int32_t)10, SEEK_SET, 99) == 10) ? 0 : 1;
],
dnl if the test program succeeds (res == 0):
[box_cv_have_lseek_dummy_param=no],
dnl if the test program fails (res != 0):
[box_cv_have_lseek_dummy_param=yes],
)]
)
if test "x$box_cv_have_lseek_dummy_param" != "xno"; then
AC_DEFINE([HAVE_LSEEK_DUMMY_PARAM], 1,
[Define to 1 if syscall lseek requires a dummy middle parameter])
fi
])
# Please note: this does not appear to work! Do not rely on it without further testing:
AC_DEFUN([AX_CHECK_SYSCALL_LSEEK_64_BIT], [
AC_CACHE_CHECK(
[[whether syscall lseek takes a 64-bit offset parameter]],
[box_cv_have_lseek_64_bit],
[AX_TRY_RUN_FD(
[
// Try to seek to a position that requires a 64-bit representation, and check the return
// value, which is the current position.
if(syscall(SYS_lseek, fd, (int64_t)5, SEEK_SET) != 5)
{
res = 2;
}
else if(syscall(SYS_lseek, fd, (int64_t)10, SEEK_CUR) != 15)
{
res = 3;
}
else
{
res = 0;
}
],
dnl if the test program succeeds (res == 0):
[box_cv_have_lseek_64_bit=yes],
dnl if the test program fails (res != 0):
[box_cv_have_lseek_64_bit=no]
)]
)
if test "x$box_cv_have_lseek_64_bit" != "xno"; then
AC_DEFINE([HAVE_LSEEK_64_BIT], 1,
[Define to 1 if syscall lseek takes a 64-bit offset])
fi
])
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