1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
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
AC_DEFUN([AX_CHECK_SYSCALL_LSEEK], [
AC_REQUIRE([AX_FUNC_SYSCALL])dnl
if test "x$ac_cv_header_sys_syscall_h" = "xyes"; then
AC_CACHE_CHECK([[whether syscall lseek requires dummy parameter]], [box_cv_have_lseek_dummy_param],
[AC_TRY_RUN(
[
$ac_includes_default
#include <fcntl.h>
#include <sys/syscall.h>
#ifdef HAVE___SYSCALL_NEED_DEFN
extern "C" off_t __syscall(quad_t number, ...);
#endif
#ifdef HAVE___SYSCALL // always use it if we have it
#undef syscall
#define syscall __syscall
#endif
int main()
{
int fh = creat("lseektest", 0600);
int res = 0;
if(fh>=0)
{
// This test tries first to seek to position 0, with NO
// "dummy argument". If lseek does actually require a dummy
// argument, then it will eat SEEK_SET for the offset and
// try to use 99 as whence, which is invalid, so res will be
// -1, the program will return zero and
// have_lseek_dummy_param=yes
// (whew! that took 1 hour to figure out)
// The "dummy argument" probably means that it takes a 64-bit
// offset, so this was probably a bug anyway, and now that
// we cast the offset to off_t, it should never be needed
// (if my reasoning is correct).
res = syscall(SYS_lseek, fh, (off_t)0, SEEK_SET, 99);
close(fh);
}
unlink("lseektest");
return res!=-1;
}
],
[box_cv_have_lseek_dummy_param=yes],
[box_cv_have_lseek_dummy_param=no],
[box_cv_have_lseek_dummy_param=no # assume not for cross-compiling]
)])
if test "x$box_cv_have_lseek_dummy_param" = "xyes"; then
AC_DEFINE([HAVE_LSEEK_DUMMY_PARAM], 1,
[Define to 1 if syscall lseek requires a dummy middle parameter])
fi
fi
if test "x$box_cv_have_lseek_dummy_param" = "xno"
then
m4_ifvaln([$1],[$1],[:])dnl
m4_ifvaln([$2],[else $2])dnl
fi
])dnl
|
