RFD: C pointer conversions that differ in unsignedness

[Mike Stump <mrs at apple dot com>]

Code such as:

void f(long *, unsigned long *);

int main()
{
    long *scp;
    unsigned long *ucp;

    ucp = scp;
    scp = ucp;
    f(ucp, scp);
}

is in violation of of the C standard.  We silently accept such code, 
unless -pedantic (or better) is given.  I didn't happen to see this 
listed in extentions.texi.

This was put in:

revision 1.91
date: 1993/05/27 04:30:54;  author: rms;  state: Exp;  lines: +6 -7
(convert_for_assignment): When allowing mixing of
signed and unsigned pointers, compare unsigned types not type sizes.

in c-typeck.c, and before that (going back to 1.1), we always gave at 
least a warning.  In C++, we give the warning.  Other compilers give 
hard errors for these things.

I propose to tighten this up to a warning, unconditionally.  How to 
others feel?  -Wall?  -std=?  Over my dead body?

Apple Radar 2535328.

Attachment: unsignedness.diffs.txt
Description: Text document