On 17 July 2015 at 10:29, Jan Doms <[email protected]> wrote:
> How about just having an accessor (and maybe also a setter) for errno?
> If I'm not mistaken such operations can not currently be written with
> ctypes and need a bit of C, right?
Right. It can *almost* be done solely in ctypes, like this:
let errno = foreign_value "errno" int
except that the C standard leaves the exact definition of errno rather
unspecified. For example, errno can be defined like this
extern int errno;
or like this
#define errno (*__internal_errno())
and the second one won't work with the above ctypes definition.
However, it's not difficult to write a couple of tiny wrappers to set
and retrieve errno:
void set_errno(int e) { errno = e; }
int get_errno(void) { return errno; }
together with ctypes bindings:
let set_errno = foreign "set_errno" (int @-> returning void)
let get_errno = foreign "get_errno" (void @-> returning int)
Some care might also be needed to ensure that nothing can change errno
between a call to a ctypes-bound function and the subsequent call to
get_errno.
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