[PATCH] Attribute parsing following labels

Richard Smith richard at metafoo.co.uk
Mon Oct 7 13:17:48 PDT 2013


Oh, also: please add test cases for #pragmas appearing near the attributes.


On Mon, Oct 7, 2013 at 1:16 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> +  // Read label attributes, if present. TempAttrs will contain both C++11
> and
> +  // GNU attributes (if present) after this point.
>
> This isn't true: we're only parsing GNU attributes here.
>
> +    } else {
> +      StmtVector Stmts;
> +      SubStmt = ParseStatementOrDeclarationAfterAttributes(Stmts, true, 0,
> +                                                           TempAttrs);
>
> This doesn't look like it'll correctly handle the case where
> ParseStatementOrDeclarationAfterAttributes returns null (because we parsed
> a pragma or the like). If you're relying on this being impossible (because
> an attribute can't apply to a #pragma), please insert an assert here (that
> SubStmt is invalid or usable).
>
>
> On Sat, Oct 5, 2013 at 2:09 PM, Aaron Ballman <aaron at aaronballman.com>wrote:
>
>> Here is another attempt at this patch, without the tentative parsing.
>>
>> Thanks!
>>
>> ~Aaron
>>
>> On Tue, Oct 1, 2013 at 12:43 PM, Richard Smith <richard at metafoo.co.uk>
>> wrote:
>> > OK, that makes some sense, since the pragma acts like a statement that
>> > cannot have an attribute.
>> >
>> > On 1 Oct 2013 05:26, "Aaron Ballman" <aaron at aaronballman.com> wrote:
>> >>
>> >> On Mon, Sep 30, 2013 at 6:03 PM, Richard Smith <richard at metafoo.co.uk>
>> >> wrote:
>> >> > It should be possible to handle this case without tentative parsing
>> or
>> >> > lookahead. Consume the attributes onto a new list; if the next token
>> is
>> >> > a
>> >> > semicolon, then push them into the label's attribute list; otherwise,
>> >> > ParseStatementOrDeclarationAfterAttributes.
>> >>
>> >> Ah, thanks!
>> >>
>> >> > What does GCC do if there are #pragmas between the case label and the
>> >> > attribute, and/or between the attribute and the semicolon?
>> >>
>> >> void func(void) {
>> >> label: __attribute__((unused))
>> >> #pragma message "stuff"
>> >> ;
>> >> }
>> >>
>> >> Prints the message, no warning about the label or the attribute.
>> >>
>> >> void func(void) {
>> >> label:
>> >> #pragma message "stuff"
>> >> __attribute__((unused))
>> >> ;
>> >> }
>> >>
>> >> Prints the message, then prints an error about expecting an expression
>> >> before the attribute, and a warning for the label being unused.
>> >>
>> >> ~Aaron
>>
>
>
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