[cfe-dev] parse C++ throw

[Mike Stump]

On Feb 25, 2008, at 2:45 PM, Chris Lattner wrote:
> +/* -*-  indent-tabs-mode:nil;  -*- */
>
> Please don't do this.

FIxed.

> +  class CXXThrowExpr : public Expr {
> ...
> +    virtual SourceRange getSourceRange() const {
> +      return SourceRange(ThrowLoc, getSubExpr()- 
> >getSourceRange().getEnd());
> +    }
>
> If getSubExpr() is null, this should return SourceRange(ThrowLoc,  
> ThrowLoc).

Ah, yes, of course.  Fixed.

> +++ ./AST/StmtPrinter.cpp	2008-02-25 13:35:57.000000000 -0800
> @@ -780,6 +780,12 @@ void StmtPrinter::VisitCXXBoolLiteralExp
>   OS << (Node->getValue() ? "true" : "false");
> }
>
> +void StmtPrinter::VisitCXXThrowExpr(CXXThrowExpr *Node) {
> +  OS << "throw ";
> +  if (Node->getSubExpr())
> +    PrintExpr(Node->getSubExpr());
>
> It would be slightly nicer to not print the space after the throw if  
> subexpr is null.

Yeah, I thought about doing that when I first implemented it and  
decided against worrying about it as it didn't seem as bad as the  
extra {} in extern "C" handling.  But, it is easy, localized and  
doesn't require any more data in the AST to do it, sooo....  Fixed.

>> I also added a FIXME for handling throw when not followed by a ';'  
>> nor an assignment-expression.  Something parser generators do  
>> automagically for us, but something we have to compute.  Do we have  
>> a tentative parse system yet or some other easy way to do this?   
>> [ I think I know the answer, I bet not. ]
>
> The fixme is fine for a first step.  However, it would be better to  
> eventually add a predicate that determines whether a token is the  
> start of an expression.

Agreed.

> I don't think there are any cases where a declaration is allowed  
> after a throw,

You mean like this:

   throw int(1);

?  Yup, that's valid.

> so this predicate should be relatively straight-forward, something  
> like Parser::isDeclarationSpecifier().
>
> I agree this is somewhat ugly, but it could be worse

Just wait, we'll get there.


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