Re: [PATCH] json: Remove invalid typedef redefinition

[Daniel Axtens]

Hi Patrick,

> The C standard does not allow for typedef redefinitions, even if they
> map to the same underlying type. In order to avoid including the
> "jsmn.h" in "json.h" and thus exposing jsmn's internals, we have exactly
> such a forward-declaring typedef in "json.h". If enforcing the GNU99 C
> standard, clang may generate a warning about this non-standard
> construct.
>
> Fix the issue by using a simple `struct jsmntok` forward declaration
> instead of using a typedef.
>
> Signed-off-by: Patrick Steinhardt <ps@pks.im>

Tested-by: Daniel Axtens <dja@axtens.net> # clang build test for emu target only

With this patch, clang can compile master again. Thanks Patrick!

Regards,
Daniel

> ---
>
> Sorry for the late response, didn't notice at first that this directly
> impacts code I wrote. I don't have Clang available on my computer and
> GCC seems to lack the equivalent option for this, so I wasn't able to
> reproduce the warning. Below patch should fix the issue, though, as we
> simply avoid using a typedef for the forward declaration.
>
>  grub-core/lib/json/json.h | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/grub-core/lib/json/json.h b/grub-core/lib/json/json.h
> index d9f99454d..2e2b0bd07 100644
> --- a/grub-core/lib/json/json.h
> +++ b/grub-core/lib/json/json.h
> @@ -36,13 +36,14 @@ enum grub_json_type
>  };
>  typedef enum grub_json_type grub_json_type_t;
>  
> -typedef struct jsmntok jsmntok_t;
> +/* Forward-declaration to avoid including "jsmn.h" */
> +struct jsmntok;
>  
>  struct grub_json
>  {
> -  jsmntok_t   *tokens;
> -  char             *string;
> -  grub_size_t idx;
> +  struct jsmntok *tokens;
> +  char                *string;
> +  grub_size_t         idx;
>  };
>  typedef struct grub_json grub_json_t;
>  
> -- 
> 2.26.2