Re: [Haskell-cafe] debugging <<loop>> exception

<<loop>> doesn't produce line numbers, since it happens at STG level while evaluating a thunk: it overwrites the entry point with the <<loop>> exception before evaluating it, so if the thunk is immediately re-entered, the <<loop>> is thrown. This is better than entering a tight loop, but not much easier to debug. On Sat, Aug 26, 2023 at 9:44 PM Ivan Perez wrote:

Sounds like a Heisenbug (turning profiling or debugging on may affect the reproducibility of the bug).

Run the program for a while with profiling enabled, and the functions involved in the infinite loop might be apparent.

Ivan

On Sat, 26 Aug 2023 at 18:33, Dennis Raddle wrote:

...

I'm getting Exception: <<loop>>.

It doesn't print the line number. When I load the program into ghci, it still doesn't print the line number. When I trace the program in ghci it never gets to the point of emitting the exception.

I set up my program in stack. I tried both "stack ghci" and just "ghci".. the latter to make sure it wasn't using any compiled code (at least in my own code). If it doesn't print a line number does this mean it's happening in compiled code?

Any ideas how I can go about debugging this?

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