Re: [PATCH 0/3] btrfs-progs: fix dropped 'const' qualifiers exposed by the latest GCC (15.2.1)

[David Sterba <dsterba@suse.cz>]

On Mon, Feb 23, 2026 at 09:42:57AM +1030, Qu Wenruo wrote:
> It looks lile the latest gcc has taken the 'const' qualifier checks one
> step further, a char pointer that points into a string that has 'const'
> qualifier should also has 'const'.
> 
> This will expose unexpected modification like the following:
> 
>  void my_func(const char *options)
>  {
>          char *dot;
> 
>          dot = strchr(options, '.');
>          if (!dot)
>                  *dot = '\0';
>  }
> 
> In above example, @dot is either NULL or points to a location inside
> @options. For the later case, since @dot itself is not const, we can
> modify the content, resulting modification of the content of @options.
> The latest GCC is able to detect such proxy modification and gives us
> warning on them.
> 
> And in fact, btrfs-progs has exactly such proxied modification in
> bconf_save_param(), fixed in the last patch by dropping the 'const'
> quailifer.
> 
> Other than that, most are just false alerts and we can fix them by
> adding a const quailifer.
> 
> Qu Wenruo (3):
>   btrfs-progs: enhance find_option()
>   btrfs-progs: constify the @dots variable inside parse_range_u64()
>   btrfs-progs: drop the 'const' qualifier from bconf_save_param()

Added to devel, thanks.