[LLVMdev] RFC: Exception Handling Proposal II

[Renato Golin]

On 25 November 2010 11:03, Duncan Sands <baldrick at free.fr> wrote:
> I don't understand what you are saying.  Cleanups (e.g. destructors)

Hi Duncan,

Cleanup landing pads normally call destructors, but they're not a
destructor themselves. I'm simply saying that compiler generated
blocks (such as cleanups) should never depend on user variables.

But I get what you're saying. If a cleanup area calls a destructor,
and destructors use user values, they have an indirect conditional
dependency that cannot be solved at compile time, unless you have a
way to normalize the call graph to disambiguate all dominance
analysis.


> I don't get what you are talking about here.  You can access any variables
> you like, whether local or global, in a catch handler.  They are not passed
> to the handler via llvm.eh.exception or llvm.eh.selector, they are simply
> accessed directly (the unwinder restores registers etc making this
> possible).

Destructors and Catch areas are user code, you could access any
variable as pleased.

Cleanup areas are compiler code, those were the ones I was talking about.


> In Ada you can throw and exception inside a destructor and it does not lead
> to program termination.

Ok, sorry. I should stop thinking C++ here.... it's difficult, but
I'll try... ;)

cheers,
--renato