On 8/9/19 10:22 AM, Jakub Jelinek wrote:
> On Fri, Aug 09, 2019 at 10:17:12AM -0600, Martin Sebor wrote:
>> --- a/gcc/gengtype-state.c
>> +++ b/gcc/gengtype-state.c
>> @@ -79,6 +79,14 @@ enum state_token_en
>>     STOK_NAME                     /* hash-consed name or identifier.  */
>>   };
>>   
>> +/* Suppress warning: ISO C forbids zero-size array for stok_string
>> +   below.  The arrays are treated as flexible array members but in
>> +   otherwise an empty struct or as a member of a union cannot be
>> +   declared as such.  They must have zero size to keep GCC from
>> +   assuming their bound reflect their size.  */
>> +#pragma GCC diagnostic push
>> +#pragma GCC diagnostic ignored "-Wpedantic"
>> +
>>   
>>   /* Structure and hash-table used to share identifiers or names.  */
>>   struct state_ident_st
>> @@ -86,11 +94,10 @@ struct state_ident_st
>>     /* TODO: We could improve the parser by reserving identifiers for
>>        state keywords and adding a keyword number for them.  That would
>>        mean adding another field in this state_ident_st struct.  */
>> -  char stid_name[1];		/* actually bigger & null terminated */
>> +  char stid_name[0];		/* actually bigger & null terminated */
> 
> No, please don't do this.  The part of the GCC that is built by system
> compiler shouldn't use GNU extensions, unless guarded only for compilation
> with compilers that do support that.

Hmm, this wasn't supposed to be in the diff anymore (the patch
handles the code without these changes).  I removed it after
verifying it just before sending the patch so my mailer must
have sent a cached copy.  Attached is the latest tested patch
without this change.

That said, we should change this code one way or the other.
There is even less of a guarantee that other compilers support
writing past the end of arrays that have non-zero size than
that they recognize the documented zero-length extension.

Martin