Re: parsing C and C++, was Compiler Compiler Compiler

"Kevin Szabo" <kszabo@nortelnetworks.com> writes:


> I've never tried to parse C/C++. Could you give an example or two
> of the problems (or point me to a reference).


Essentially, the lexical analysis needs access to the symbol table.
Consider


    a*b;


What is that: an expression statement, or a declaration? It depends:
If a is a type-name, then it is a declaration (of a variable b which
is a pointer to a). If a is not a type-name, then it is a
multiplication expression. This is already a problem in C.


C++ adds a new version of this problem; consider


    A<B,C>D;


If A is a template, then A<B,C> is a type name, and the entire thing
is a declaration (of a variable D). Otherwise, it is an expression.


There are other problems which are outright ambiguities in the syntax.


> The problems I have seen with some parsing strategies is having the
> lexer bind a symbol before it gets to the parser, that is trying
> to lookup in the symbol tables and resolving whether a token is a
> varible/type/unbound before it hits the parser.


That is what the C++ standard mandates.


Regards,
Martin

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