Re: [Gawkextlib-users] New API

[Vinícius d. S. O. <vin...@gm...>]

Em sex., 25 de jun. de 2021 às 10:07, Andrew J. Schorr
<as...@te...> escreveu:
> I'm not sure that I understand what "rule" means in an awk script.
> From the POSIX spec:
>
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html
>
>    An awk program is composed of pairs of the form:
>
>    pattern { action }
>
> So what's a "rule"? In the source code, it appears that the word "rule"
> is used to refer to the combination of a pattern and an action. So
> is the idea that this API hook would depend on detecting whether a combined
> pattern & action is present?

I mean the pattern. On plugin startup, I want to traverse all the
program rules to check if any pattern in them matches the AST
"somevar".

I'll code the plugin's behaviour to depend on whether such a rule
exists in the program. The end result gives an approximation of what's
offered by BEGINFILE rules to deal with errors on single files, but
for record-level errors.

> The implementation of BEGINFILE and ENDFILE requires a lot of
> special support in the interpreter. It seems to me that implementing
> this sort of thing requires diving into the guts of how a program
> is compiled in awkgram.y, which is quite frankly an area of the
> code that I've never messed with. In main.c, the program is parsed
> into code_block:
>
> INSTRUCTION *code_block = NULL;
> ...
>         /* Read in the program */
>         if (parse_program(& code_block, false) != 0 || dash_v_errs > 0)
>                 exit(EXIT_FAILURE);
>
> And then it runs the program by calling interpret(code_block).
>
> So any info about the running program would have to be extracted by
> parsing the INSTRUCTION data pointed to by code_block, as far
> as I can tell.

Thanks for the pointer.

Now I know where to start.


-- 
Vinícius dos Santos Oliveira
https://vinipsmaker.github.io/