Add a `--dwarf` flag for DWARF debugging

[radix]

Say I wanted to build my project with all the debugging options, including stuff like DWARF data. The page about DWARF support in GHC says that you have to pass -g to ghc to get it to generate these symbols, but what about all the packages I depend on, and the RTS itself? ("you will need to compile both libraries and the runtime system with debugging support (GhcRtsHcOpts += -g and GhcLibHcOpts += -g).") I guess to make it easy to have a GHC RTS with debugging we'd need bindists that have symbols in them -- I'm not sure if the default 7.10.2 ones have them.

Likewise all this stuff for GHC's profiling options. Is there a way to easily just turn on all profiling options for a project and rebuild everything so I can profile everything?

Maybe this is already pretty easy and this should just be resolved with some documentation in the guide.

[snoyberg]

master has support for setting arbitrary ghc-options in your stack.yaml file:

https://github.com/commercialhaskell/stack/wiki/stack.yaml#ghc-options

I can't speak to the settings used by the official bindists, however.

[radix]

Thanks for the note. I think it'd be nice to mention this specifically with respect to "debugging" and/or "profiling" in the Guide. (I specifically just did a search for the words "profile" or "debug" in the guide and didn't find one). I'd try to put together a PR (as evinced by the time it took to respond to you on this ticket) I am lacking time.

[GregorySchwartz]

I'll write up a brief explanation about using ghc options to profile.

[gambogi]

Is this issue still open?

[borsboom]

@gambogi The documentation that @GregorySchwartz wrote doesn't address the DWARF case. I'm guessing it's too early in development for Stack to really support that case well anyway, but I haven't done any research into it (e.g. whether GHC 7.10.2 bindists include DWARF debugging info -- I'm assuming they don't). The profiling docs that @GregorySchwartz added look good but also don't cover using -fprof-auto and +RTS -xc to get rudimentary stack traces (without DWARF info), so that could potentially be improved.