Re: representing C++ constructors in GDB's symbol tables

[Daniel Jacobowitz <drow at false dot org>]

On Fri, Sep 17, 2004 at 05:45:40PM -0500, Jim Blandy wrote:
> 
> There are currently several problems I see in the way we represent C++
> constructors in GDB's symbol table.
> 
> First, for a class named "X", we put three (or possibly four) entries
> in VAR_DOMAIN all named "X": the typedef, and two (or possibly three)
> constructors.  This makes it (cough) difficult to look up the one you
> need.
> 
> It occured to me that perhaps constructors should not be in the
> VAR_DOMAIN.  You can't use them by name in expressions: you have to
> say "new X(...)", never "X(...)".  You can't call them directly.  You
> can't take their addresses: "&X::X(int)" is not valid C++.  The only
> reason they really have names at all is to let you define them outside
> the class.
> 
> Creating a new CONSTRUCTORS_DOMAIN would give you something reasonable
> to pass when handling a "new" expression.  And there's nothing wrong
> with adding a C++-specific domain; domains were created to distinguish
> the different roles identifiers might play in a particular language:
> witness STRUCT_DOMAIN vs VAR_DOMAIN for C.

I prefer fixing the names of the constructors in the symbol table (or
un-flattening the symbol table); I think that would obsolete this.

> Then there's the question of duplicate copies of the constructors
> themselves.  The code at the moment wants to distinguish them by their
> physical (linker) names, but I gather one of the main thrusts of David
> and Daniel's work was to move away from the internal use of mangled
> names for this kind of thing.  Domains are the wrong tool there; the
> presence of multiple constructor copies is an ABI-specific thing.
> I don't have an answer to that that sounds good yet. 

We only need to have textual names that distinguish these things for
the user interface.  Internally, they can just be different pointers;
that means we have to keep track of them from the types rather than
storing names in the types and abusing lookup_symbol.

-- 
Daniel Jacobowitz