Hi Martin,
On Sun, Jul 07, 2024 at 09:15:23AM GMT, Martin Uecker wrote:
>
> Hi Alejandro,
>
> if in caller it is known that endptr has access mode "write_only"
> then it can conclude that the content of *endptr has access mode
> "none", couldn't it?
Hmmmm. I think you're correct. I'll incorporate that and see how it
affects the caller.
At first glance, I think it would result in
nptr access(read_only) alias *endptr
endptr access(write_only) unique
errno access(read_write) unique
*endptr access(none) alias nptr
Which is actually having perfect information, regardless of 'restrict'
on nptr. :-)
> You also need to discuss backwards compatibility. Changing
> the type of those functions can break valid programs.
I might be forgetting about other possibilities, but the only one I had
in mind that could break API would be function pointers. However, a
small experiment seems to say it doesn't:
$ cat strtolp.c
#include <stdlib.h>
long
alx_strtol(const char *nptr, char **restrict endptr, int base)
{
return strtol(nptr, endptr, base);
}
typedef long (*strtolp_t)(const char *restrict nptr,
char **restrict endptr, int base);
typedef long (*strtolpnr_t)(const char *nptr,
char **restrict endptr, int base);
int
main(void)
{
[[maybe_unused]] strtolp_t a = &strtol;
[[maybe_unused]] strtolpnr_t b = &strtol;
[[maybe_unused]] strtolp_t c = &alx_strtol;
[[maybe_unused]] strtolpnr_t d = &alx_strtol;
}
$ cc -Wall -Wextra strtolp.c
$
Anyway, I'll say that it doesn't seem to break API.
> You would
> need to make a case that this is unlikely to affect any real
> world program.
If you have something else in mind that could break API, please let me
know, and I'll add it to the experiments.
Thanks!
Have a lovely day!
Alex
--
<https://www.alejandro-colomar.es/>
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