Re: Data con names in the debugger

Simon Peyton-Jones wrote:

> I saw that Ian committed your patches -- great!
> 
> Concerning the recovery of DataCon names, you write "The closure viewer
> obtains the heap address of a Haskell value, find out the address of its
> associated info table, and trace back to the DataCon? corresponding to this
> info table. This is possible because the ghc runtime allocates a static info
> table for each and every datacon, so all we have to do is extend the linker
> with a dictionary relating the static info table addresses to a DataCon?
> name. Moreover, the ghci linker can load interpreted code containing new data
> or newtype declarations. So the dynamic linker code is extended in the same
> way."
> 
> Isn't there a simpler way to do this: just include the DataCon name in the
> info table of the data con.  Of course that makes every (debuggable) binary a
> bit bigger, but so does all the breakpoint stuff.

Maybe.  Doing this just for datacons wouldn't be so bad in terms of bloat, and 
it'll be necessary anyway if we're using the systems dynamic linker rather than 
the RTS linker, which is the case when using shared libraries.  The system 
dynamic linker can't in general map addresses back to symbol names.

Pepe: while browsing the code, I noticed you're using an association list for 
the AddressEnv - it would be better to use a FiniteMap here (or maybe even a 
UniqFM).

Cheers,
	Simon