Feature request: Print backtrace in `trace` output

[bgamari]

The builtins.trace function is quite handy for probing state buried deep within a derivation. However, while trying to understand a cross-compiling bug I've seen my trace output printed multiple times. Without a stack backtrace (e.g. what throw would produce with --show-trace) this is quite difficult to interpret.

[copumpkin]

This seems cool and possibly not too hard to add. I'd probably make a new builtin for it though, like builtins.dumpStack which behaves like the identity function except dumps a stack trace when forced. I don't necessarily want a stack dump in every trace output, and we can't really change the API much. What you're asking then would be a composition of builtins.trace and builtins.dumpStack

[stale]

I marked this as stale due to inactivity. → More info

[milahu]

push : )

I'd probably make a new builtin for it though, like builtins.dumpStack which behaves like the identity function except dumps a stack trace when forced.

plus: something like builtins.callStack to get a list of the current callstack,
which can be manually reduced to, for example, the last 5 entries, to avoid printing "too long" stacktraces

edit: oh wait, that would be impure ...

[stale]

I marked this as stale due to inactivity. → More info