Re: [Tinycc-devel] _Generic or __builtin_choose_expr

[uso ewin]

I'd like to do that, problem is with default:
if we encounter a default,
we need to remember that there is a default in the generic,
but we need to continue parsing generic expression to check
if there is a type that match, and with you technique we can't go back and
re-evaluate default if at the end, no match was found.

example:
int a = _Generic(a, default: 3, char : '_', int : 1);


On Fri, Jun 30, 2017 at 5:25 PM, Michael Matz <address@hidden> wrote:
> Hi,
>
> On Fri, 30 Jun 2017, uso ewin wrote:
>
>> I've clean my commit and merge everything on my my mob which should be
>> easily mergeable with official mob:
>> https://github.com/cosmo-ray/tcc/commit/d2659993274e076894e039cc654fc9e1617ed056
>
> Yeah, already nicer.  More suggestions below:
>
>> > I've very briefly looked at your implementation: Don't use your
>> > current way of parsing the controlling expression/type, you should be
>> > able to reuse expr_type/parse_expr_type/parse_type (or parts of it).
>>
>> Thanks for your advice, and done on mob branch on my github, expr_type
>> work great.
>>
>> As buying the official C11 standard from ISO is a little expensive for
>> my, I use this draft for the implementation:
>> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf
>
> n1570 is the most recent draft before finalization of the standard.  But
> I guess for _Generic it doesn't matter.  Now for the suggestion:
>
> Instead of saving the tokens for the matching expression and evaluating it
> after completely parsed, use the nocode_wanted facility to enable or
> disable code generation for the matching and non-matching expressions.
> Ala:
>
>   while (1) {
>     parse type
>     if (type matches)
>       expr_eq();
>     else {
>       nocode_wanted++;
>       expr_eq();
>       vpop();
>       nocode_wanted--;
>     }
>   }
>
> (Obviously with all the added checking you already have in there for
> double defaults or twice-matching types).
>
> That should further simplify the code and make it nicer.
>
>
> Ciao,
> Michael.
>
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