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SubjectRe: [RFC] strcpys(): New function for copying strings safely
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On 6/27/21 9:26 PM, Alejandro Colomar (man-pages) wrote:
>
> It is designed so that usage requires the minimum number of lines of
> code for complete usage (including error handling checks):
>
> [[
> // When we already checked that 'size' is >= 1
> // and truncation is not an issue:
>
> strcpys_np(size, dest, src, NULL);

Also, given how unlikely this case is, I have in my code:
`[[gnu::warn_unused_result]]`

I forgot to talk about it in the definition I sent. I would put that
attribute in the glibc definition, if this is added to glibc.

To ignore it, a simple cast of the result to `(void)` should be enough
(or a more complex macro, like `UNUSED(strcpys_np(...));`).
>
> [[
>
> #include <string.h>
> #include <sys/types.h>
>
>
> [[gnu::nonnull]]
> ssize_t strscpy_np(ssize_t size,
>                    char dest[static restrict size],
>                    const char src[static restrict size])
> {
>     ssize_t len;
>
>     if (size <= 0)
>         return -1;
>
>     len = strnlen(src, size - 1);
>     memcpy(dest, src, len);
>     dest[len] = '\0';
>
>     return len;
> }
>
> [[gnu::nonnull(2, 3)]]
[[gnu::warn_unused_result]]
> int strcpys_np(ssize_t size,
>                char dest[static restrict size],
>                const char src[static restrict size],
>                ssize_t *restrict len)
> {
>     ssize_t l;
>
>     l = strscpy_np(size, dest, src);
>     if (len)
>         *len = l;
>
>     if (l == -1)
>         return -1;
>     if (l >= size)
>         return 1;
>     return 0;
> }
>
> ]]

--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

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