Bug report : fcntlmodule.so (fonction ioctl) python 1.5.2

[Guido van Rossum]

IMPORTANT NOTE: please report all bugs via the Python Bugs List on the
web: http://www.python.org/search/search_bugs.html.  This lets you
search to find out whether the bug was already reported (and if so, if
there was a fix); it also requests important information like platform
and Python version.

David Berthelot <berthelo at lirmm.fr> writes:

> i think, i found a bug (and a fix).
> 
> In the "fcntlmodule.so", the "ioctl" function does not work with 
> an optional int parameter but currently it works only with an 
> optional string parameter.
> 
> So i think that the line number 76 of fcntlmodule.c :
> 76: ret = ioctl(fd, code, arg);
> 
> should be replaced by:
> 76: ret = ioctl(fd, code, &arg);
> 
> I think it does it, doesn't it ? 
> Yes, unlike fcntl, ioctl uses a pointer for its 3rd arg.

Which ioctl command were you using?  Whether arg must be an int or a
pointer to an int or a pointer to something else depends on which
command you are issuing.

If you need a pointer to an int, I recommend using the struct module
to convert it to a string.  E.g. (untested) something like:

import struct, fcntl

def ioctl_p_int(fd, request, value):
    s = struct.pack("i", value)
    s2 = fcntl.ioctl(fd, request, s)
    (ret,) = struct.unpack("i", s2) # this always returns a tuple
    return ret

--Guido van Rossum (home page: http://www.python.org/~guido/)