[cfe-commits] r58100 - in /cfe/trunk: lib/Sema/SemaDecl.cpp test/SemaCXX/fntype-decl.cpp

[Doug Gregor]

On Sat, Oct 25, 2008 at 3:38 PM, Ted Kremenek <kremenek at apple.com> wrote:
>
> On Oct 25, 2008, at 2:07 AM, Argiris Kirtzidis wrote:
>
>>> It does seem odd that we're destroying the TypedefDecl before
>>> destroying the FunctionDecl but I'll look into it.
>>>
>>
>> TranslationUnit destroys the decls at the order of  receiving them, should
>> that be reverse order ?
>
> The order shouldn't matter if we have a clear ownership policy.  While
> TranslationUnit may free AST nodes in a particular order, there's no reason
> to expect that when clients create and free AST nodes that they do it in a
> particular order either.  The only requirement is that memory that is freed
> is no longer accessed.

I don't think the ownership policy would necessarily clear this up.
For ownership to solve this problem, we would need to have the
FunctionDecl "own" the TypedefDecl that is used to express it's type.
It can't have sole ownership, of course, since another FunctionDecl
might use it as the type.

There are a few solutions here. One easy option, which I've committed
already as a band-aid, is as Argiris said: destroy the decls in
reverse order. Since a Decl should only depend on Decls before it,
this works. Another alternative is to ban destructors that look
through any non-owned pointer; for example, this would mean that
FunctionDecl would have to have its own NumParams field rather than
looking through its type field to find the number of parameters. Then,
order of destruction would never matter.

  - Doug