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Re: [Tinycc-devel] match formats and arguments exactly
From: |
Vincent Lefevre |
Subject: |
Re: [Tinycc-devel] match formats and arguments exactly |
Date: |
Fri, 21 Jun 2019 18:49:34 +0200 |
User-agent: |
Mutt/1.12.1+19 (078654a4) vl-117499 (2019-06-15) |
On 2019-06-21 15:33:24 +0200, Christian Jullien wrote:
> If I read you correctly, you want to protest if type does not
> strictly match format directive.
>
> This is something even gcc does NOT ensure by default:
[...]
This is undefined behavior, and the compiler is not required
to complain. This can just mean that your code will silently
be compiled in an unexpected way.
[...]
> int i = 256;
>
> const char* s = "Hello";
>
> const void* p = s;
>
>
>
> printf("%x\n", i);
>
> printf("%u %s\n", i, p);
[...]
> Only -Wformat (or -Wall) shows a warning on the 2nd printf, printf
> of i (a signed) is always Ok.
I don't think this is correct for i as int and unsigned int are not
compatible types... even though 256 has the same representation as
int and unsigned int (I think that the C standard should have been
more flexible in such a case).
--
Vincent Lefèvre <address@hidden> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
- Re: [Tinycc-devel] match formats and arguments exactly, (continued)
- Re: [Tinycc-devel] match formats and arguments exactly, Christian Jullien, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly, C.J. Wagenius, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly, Ivo van Poorten, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly, Vincent Lefevre, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly, Larry Doolittle, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly, Pascal Cuoq, 2019/06/21
- Re: [Tinycc-devel] match formats and arguments exactly,
Vincent Lefevre <=
Re: [Tinycc-devel] match formats and arguments exactly, Michael Matz, 2019/06/21