C Compiler in C++

stanarevic@hotmail.com (Nemanja Stanarevic)
8 May 2002 00:15:31 -0400

          From comp.compilers

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C Compiler in C++ stanarevic@hotmail.com (2002-05-08)
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Re: C Compiler in C++ thp@cs.ucr.edu (2002-05-12)
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From: stanarevic@hotmail.com (Nemanja Stanarevic)
Newsgroups: comp.compilers
Date: 8 May 2002 00:15:31 -0400
Organization: http://groups.google.com/
Keywords: C, question
Posted-Date: 08 May 2002 00:15:31 EDT

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

Nemanja Stanarevic

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