[M3devel] how to use gcc exception/unwind support?

[Tony Hosking]

My take was that we would use the unwind support with RTExStack along with recording the flow constraints for the IR.  They were never that tricky.

On Jan 2, 2011, at 3:29 AM, Jay K wrote:

> Tony et. al. do you have much idea already in mind of what using gcc exception and/or unwind support would look like?
> 
> 
> In particular, do you think we could/should/would use
> TRY_CATCH_EXPR, TRY_FINALLY_EXPR? I'm not sure (see below).
> 
> 
> Do you understand the difference between WITH_CLEANUP_EXPR and TRY_FINALLY_EXPR?
> I don't. Maybe WITH_CLEANUP_EXPR captures a common case is very similar?
> 
> 
> Regarding TRY_CATCH_EXPR, TRY_FINALLY_EXPR, they sound very promising.
> But does CATCH_EXPR provide the right construct for deciding to catch or not,
> and passing the exception properly to the handler?
> 
> 
> Or should we use RTExStack nearly or completely unchanged, but:
>  1) have it call libgcc/libunwind, via interface RTStack.
>  2) in the backend mimic TRY_CATCH_EXPR, TRY_FINALLY_EXPR's affects/pessimisations
>   on the control flow graph and such?
>    
> 
> Related question is how to model throwing an exception in the backend.
> This I had looked at even less (e.g. trying to understand how g++ uses this stuff) but is clearly important.
> g++ clearly sometimes calls __cxa_throw, not clear if it always does.
> Not clear it does anything else in terms of informing the backend. It looks like not.
> 
> 
>  - Jay
> 

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