Symbol table for complex data structure

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1

Hi,

[Apologies, forgot to reply to list]

No, it's not LLVM specific, but I'll have a go at answering anyway.

The symbol table (in an AST, I assume?) deals with *symbols*. Assuming
your complex datatype is called a "struct" for simplicity's sake, your
symbol table would normally just store the struct's name, along with its
AST node.

Unless you want specific handling for static-style data member accesses
(MyClass::my_static_member in C++), there is no need to add each element
in the struct to the symbol table. The main reason for this is that it
holds no semantic value:

* A struct S is a specific type, which can be instantiated. It would
therefore be added to the symbol table as it can be referred to by code
(my $s = new S).
* A struct member S.m has a type, and a name, but is specific to an
instantiation of the wrapper type S. It holds no semantic meaning to
store S.m in the symbol table, as two S.m's may not refer to the same
node, as the parent S may be different (my $s = new S; my $s2 = new S;
$s.m == $s2.m).
* Unless you want to handle static data members, but personally I handle
them as special cases.
* Not only this, but with more complex datatypes such as classes, which
can have virtual functions, $s1.m() may in fact refer to T.m(), where T
extends S. Therefore a special-case lookup for datatype members is what
I would recommend, instead of trying to match them directly via the
symtab.

I hope this answers your question.

James

> From: llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-
bounces@cs.uiuc.edu]
> On Behalf Of leledumbo
> Sent: 01 November 2010 09:41
> To: llvmdev@cs.uiuc.edu
> Subject: [LLVMdev] Symbol table for complex data structure
>
>
> Maybe this is not LLVM specific, but more or less related. The
language
> I'm
> implementing allows the programmer to define complex data structure
> like
> Pascal records. How am I suppose to design the symbol table? What
> should be
> recorded there? Just the type name or each of the record element

must

> be
> stored?
> --
> View this message in context:

http://old.nabble.com/Symbol-table-for-

2

The symbol table (in an AST, I assume?) deals with *symbols*. Assuming
your complex datatype is called a "struct" for simplicity's sake, your
symbol table would normally just store the struct's name, along with its
AST node.

Actually, I don't put it along with the AST. It's a separate class in
separate module, should it be integrated?
Hmm... storing the AST node might be a good idea, I was duplicating the
information by copying the declaration line, type, etc. as the symbol table
entry. This is the point where I got confused in complex data type.

3

Hi,

As far as encapsulation is concerned, that's your decision (and sticking
the Symtab in a separate class is a good idea). I was more checking that
this symbol analysis is being done *on* your AST - so at the AST phase
of compilation.

James

From: llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu]
On Behalf Of leledumbo
Sent: 01 November 2010 10:17
To: llvmdev@cs.uiuc.edu
Subject: Re: [LLVMdev] Symbol table for complex data structure

> The symbol table (in an AST, I assume?) deals with *symbols*.
Assuming
> your complex datatype is called a "struct" for simplicity's sake,
your
> symbol table would normally just store the struct's name, along with
its
> AST node.

Actually, I don't put it along with the AST. It's a separate class in
separate module, should it be integrated?
Hmm... storing the AST node might be a good idea, I was duplicating

the

4

I was more checking that this symbol analysis is being done *on* your
AST - so at the AST phase of compilation.

Ah, yes it is (on where else it could be?).