Henning Thielemann
On Fri, 8 May 2020, Niklas Hambüchen wrote:
On 5/8/20 7:32 PM, Henning Thielemann wrote:
Can someone please give me examples where current state lacks
* Currently stack traces are not printed, so users cannot forward them to the developer, even if both the users and the developers would like that.
We are talking about the HasCallStack stack traces, yes? How is their emission addressed by extending exceptions with stack traces?
HasCallStack stack traces are one type of backtrace that the proposal supports. However, it's not the only (nor is it even the most useful sort, in my opinion). Other mechanisms include cost center stacks from the cost-center profiler and native stack unwinding.
* Developers cannot easily produce stack traces do debug unintended exceptions.
What are "unintended exceptions"? What is an example of an "unintended exception"?
For instance, * Somewhere deep in my code a colleague used `fromJust` due to a miscommunicated invariant * Somewhere in my system a `writeFile "tmp" $ repeat 'a'` failed due to filling the disk * Somewhere in my system I have a partial pattern match in a module which was compiled without -Wall * Somewhere in my system I `div` by zero due to lack of input validation * I use a record selector on a sum. * A logic error results in an assertion failure deep in my program, but it's unclear which path my program took to arrive at the assertion This list could go on and on... Currently the proposal does not cover asynchronous exceptions but it wouldn't be particularly hard to extend it in this direction. This would allow far better reporting of heap/stack overflows and MVar deadlocks (which are particularly hard to debug at the moment). Cheers, - Ben