On 2022/01/03 10:26, Dmitry Osipenko wrote:

03.01.2022 03:41, Hector Martin пишет:

quoted

quoted

There is indeed no need for the castings in such cases, it's a typical
code pattern in kernel. You would need to do the casting for the other
way around, i.e. if char ** was returned and **alt_paths was a const.

You do need to do the cast. Try it.

$ cat test.c
int main() {
        char *foo[1];
        const char **bar = foo;

        return 0;
}

$ gcc test.c
test.c: In function ‘main’:
test.c:4:28: warning: initialization of ‘const char **’ from
incompatible pointer type ‘char **’ [-Wincompatible-pointer-types]
    4 |         const char **bar = foo;
      |

You can implicitly cast char* to const char*, but you *cannot*
impliclicitly cast char** to const char** for the reason I explained. It
requires a cast.

Right, I read it as "char * const *". The "const char **" vs "char *
const *" always confuses me.

Hence you should've written "const char **alt_paths;" in
brcm_alt_fw_paths() in the first place and then casting wouldn't have
been needed.

Sure, in this case that works since the string is just strduped and
never mutated. Either way this will change to an argument instead of a
return value, since I'll change it to be statically sized as you said
and allocated by the caller (or in the struct).

-- 
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub