C Compiler in C++

Dear colleagues -
I am writing a complete C compiler in C++ as an academic exercise and
I need an advice related to the design of parse tree data structure
for C declarations.


I organized the parse tree so that class PTN (Parse tree node) is a
super-class for all node classes. Than, I derive nodes such as
PTNBinaryOperation, PTNAssignment, PTNIf, PTNSequence (sequence of
statements), etc. Please note that in this implementation a node can
have 0..n children.


However, I have no idea how to go about representing C variable
declarations in the parse tree. The problem is that C grammar itself
is very loose on rules for variable declarations. For example: extern
int const unsigned volatile static foo; is syntactically correct, but
semantically doesn't make sense. Also, int const const const const
usigned bar; is both syntactically and semantically correct, but
should emit a warning about multiple const qualifiers.


It almost looks like that I have to have a parse tree node class for
each production in C grammar related to declarations (such as:
declaration, declaration_list, declaration_specifiers,
init_declarator_list, etc.). Once this parse tree is generated, I
would have to go trough that structure and derive declarations in
terms of typing system that I have in place (class hierarchy to
support basic types, pointers to types, structs, unions, arrays of
types, etc.) and report errors/warnings. But this is so terribly ugly
- there is way too many parse tree nodes that need to be defined, and
it seems redundant since I already have type hierarchy in place.


Does anyone know of a good way (or generally accepted way) of
representing the parse tree for C declarations using a similar class
hierarchy?


Thanks,
Nemanja Stanarevic

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