Re: [Tinycc-devel] Variable declaration as first statement in a 'case' block gives error.

[Herman ten Brugge]

On 1/18/24 22:08, grischka wrote:
> On 18.01.2024 17:38, Herman ten Brugge via Tinycc-devel wrote:
> > That depends on the version of gcc / clang.
> > Gcc 13.2.1 prints no error.
> > Clang 17.0.6 prints "error: expected expression"
> > Clang 18.0.0(not released yet) prints "warning: label followed by a 
> > declaration is a C23 extension [-Wc23-extensions]"
> >
> > I probably should have mentioned it when committing the fix.
>
> Maybe yes.
>
> Plus mention that it's not a fix, but an experiment
> with undocumented non-standard syntax.
>
> Plus mention the benefit and the price too, please.
>
> Plus while at it, spend some thoughts first:
>
> -                } else {
> +                } else if (!decl(VT_JMP)) {
>                      gexpr();
>                      vpop();
>
>
> Hm... just one line changed.  But wait, does not tcc look
> for decl before expression already?  Sure it does because
> it supports C99.  Why now look twice ?  And why skip parsing
> the expression if where was a declaration?  What's the point?
> Who wrote that?
>
> Let's maybe try to use the tcov for tcc (which as we know was
> you who wrote it and is really not bad btw):
>
> $ tcc -ftest-coverage ../tcc.c -o tcc1.exe && tcc1.exe ../tcc.c -o 
> tcc2.exe
>
> tcc1.exe.tcov:
>        -: 0:Function:decl 68.67%
> Before:
>   10701: 8417: int v, has_init, r, oldint;
> After:
>   18408: 8417: int v, has_init, r, oldint;
>
> We note 7707 additional (+72%) calls for decl(),
>
>       183: 7247:    block_after_label:
>      1006: 7248:              {
>
> and that however only 1006 labels/cases/defaults were seen
> at all.
>
> Also we note no "label: decl" in tcc anywhere and also in
> noone elses code we've seen so far (the OP's doesn't count
> because it's generated C IIUC)
>
> Now back to the "benefit vs. price" question ...
I wanted to avoid an extra check for ';' because I found code like:

    case xxx: ; }

Instead of writing 'break;' they used ';'.
Without checking for ';' a warning was printed:
deprecated use of label at end of compound statement

So how about the next patch:
C23: Implement declaration after label (see attached patch)

    Herman

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