Re: [PATCH/WIP 1/8] wrapper: implement xopen()

From: Paul Tan <pyokagan@gmail.com>
Date: Jun 3, 2015, 08:16 UTC
Message-ID: <CACRoPnSk7vgFwTazEz3yytsdBC0CT+Yjs3JZ_oX_kuR2yyZhRA@mail.gmail.com>
In-Reply-To: <20150527215307.GC23259@peff.net>

On Thu, May 28, 2015 at 5:53 AM, Jeff King <peff@peff.net> wrote:

Show 17 quoted lines

> On Wed, May 27, 2015 at 09:03:47PM +0200, Torsten Bögershausen wrote:
>
>> The original open can take 2 or 3 parameters, how about this:
>> int xopen(const char *path, int oflag, ... )
>> {
>>         va_list params;
>>         int mode;
>>         int fd;
>>
>>         va_start(params, oflag);
>>         mode = va_arg(params, int);
>>         va_end(params);
>>
>>         fd = open(path, oflag, mode);
>
> Don't you need a conditional on pulling the mode arg off the stack
> (i.e., if O_CREAT is in the flags)?

Yeah, we do, as va_arg()'s behavior is undefined if we do not have the next argument.

The POSIX spec[1] only mentions O_CREAT as requiring the extra argument, so I guess we'll only need to check for that.

[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html

Thanks, Paul