NetBSD Problem Report #57809

From www@netbsd.org  Mon Jan  1 22:03:46 2024
Return-Path: <www@netbsd.org>
Received: from mail.netbsd.org (mail.netbsd.org [199.233.217.200])
	(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits))
	(Client CN "mail.NetBSD.org", Issuer "mail.NetBSD.org CA" (not verified))
	by mollari.NetBSD.org (Postfix) with ESMTPS id DB5E91A9238
	for <gnats-bugs@gnats.NetBSD.org>; Mon,  1 Jan 2024 22:03:45 +0000 (UTC)
Message-Id: <20240101220344.C07921A9239@mollari.NetBSD.org>
Date: Mon,  1 Jan 2024 22:03:44 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: FD_ZERO is type-unsafe
X-Send-Pr-Version: www-1.0

>Number:         57809
>Category:       lib
>Synopsis:       FD_ZERO is type-unsafe
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 01 22:05:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The SetFD Foundation
>Environment:
>Description:
FD_ZERO in sys/select.h accepts arguments of any pointer type, not just fd_set *.

The other FD_* functions (FD_SET, FD_CLR, FD_ISSET) are also moderately type-unsafe, in that they accept a pointer to any struct or union that has a member called `fds_bits' of an appropriate type.
>How-To-Repeat:
$ cat pr.c
#include <sys/select.h>

fd_set readfds;

void
setup(int readfd)
{
	FD_ZERO(&readfd);
	FD_SET(readfd, &readfds);
}
$ make pr.o DBG=-g\ -O2\ -Wall\ -Wextra\ -Werror
cc -g -O2 -Wall -Wextra -Werror   -c pr.c
$ 

This should report a type error, but it does not.  Instead, because of the typo, it silently overwrites the local variable `readfd' and, for any input other than 0, puts the wrong fie descriptor into the fd set `readfds'.
>Fix:
Yes, please!

Maybe these should just be redefined as inline functions instead of as macros.

Home	PR Database Search