GHCi debugger status

Simon Marlow marlowsd at
Fri Nov 21 05:55:00 EST 2008

Daniil Elovkov wrote:

> I'd like to know, how do ghc developers and users feel about the debugger?
> I'm using it to some extent on ghc 6.8.2 and find it useful. But I'm 
> getting an impression that it's not too stable. I'm not filing any bug 
> report yet, just want to know how it feels for others.
> I used to make it panic. I think, it was due to existential types.
> Now I see it mess up the list of bindings in a funny way. For example, 
> in a previous trace session I had a variable, say, prev. It was bound 
> during pattern matching in a function, say, prevFunc. Now I'm having 
> another trace session, actually stepping from the very beginning. A 
> couple of steps after the beginning, prev suddenly appears in the 
> bindings where prevFunc absolutely has not yet been invoked. It's 
> completely unrelated. In 'show bindings' prev has a wrong type - 
> SomeType (it's ADT). Its real type (when in scope) is [t]. I ask 'length 
> prev' and get 0 :)
> So, what is your impression of the debugger?

Please file bug reports!


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