Re: [Tinycc-devel] Bug that TinyCC Analyses Strings inside #if 0 blocks

[Vincent Lefevre]

On 2022-07-12 06:57:41 +0800, Ziyao wrote:
> On Mon, Jul 11, 2022 at 05:47:31PM +0200, Domingo Alvarez Duarte wrote:
> > Hello Ziyao !
> > 
> > Although gcc compiles a file containing your example with warnings, I'm not
> > sure it's worth try to do the same in TiinyCC the preprocessor probably uses
> > TOKENS from the lexer to decide to skip till the end of the initial "#if 0"
> > and '"' is not a valid token the error probably come from the lexer that
> > found a non terminated string.
> > 
> For conditional inclusion,C99 document says:
>       Only the first group whose control condition evaluates to true
>       (nonzero) is processed. If none of the conditions evaluates to true,
>       and there is a #else directive, the group controlled by the #else is
>       processed; lacking a #else directive, all the groups until the
>       #endif are skipped.1
> In my understanding,the skipped part should NOT be processed.

To be able to skip it, the compiler needs to parse it as described
in 6.10. So code like

#if 0
#if 1
#else
foo
#endif
#else
OK
#endif

should give OK. And if anything violates the syntax during parsing,
one should get a diagnostic.

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Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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