> should I end the function
>
> sqlite3_result_blob(ctx,blob,50,SQLITE_TRANSIENT);
> free(blob);
>
> or
>
> sqlite3_result_blob(ctx,blob,50,free);
>
> While the latter would save sqlite having to create a copy of the blob I'm a bit worried about the function being called multiple times in the same sql statement e.g.
>
> select fct(..), fct(..), fct(..), fct(..), fct(..);
> and the frees building up. Am I worrying about nothing?
Either of those two is correct. The difference in performance is most likely too small to worry about, unless your application is super performance-critical. No need to worry about the "frees building up" either. Using SQLITE_TRANSIENT might make the code easier to grok, but I think it's a matter of taste more than anything.
> Also, is the use of SQLITE_TRANSIENT a necessity if the memory will be automatically freed at the end of the function? e.g. in the case of
> char blob[50]={...};
It is, yes. Otherwise SQLite will try to use the buffer after it has been automatically freed.