July 2022 - ghc-devs - Haskell.org

Tracking intermittently failing CI jobs
by Bryan 12 Jul '22

12 Jul '22

Hi all, I'd like to get some data on weird CI failures. Before clicking "retry" on a spurious failure, please paste the url for your job into the spreadsheet you'll find linked at https://gitlab.haskell.org/ghc/ghc/-/issues/21591. Sorry for the slight misdirection. I wanted the spreadsheet to be world-writable, which means I don't want its url floating around in too many places. Maybe you can bookmark it if CI is causing you too much trouble. :) -Bryan

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Hadrian
by Simon Peyton Jones 11 Jul '22

11 Jul '22

I am working on a branch of GHC, actually on !8210. I have rebased on master. Then I say

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Re: 9.4.1 Final Call
by Ryan Scott 05 Jul '22

05 Jul '22

One thing that wasn't included in the list but arguably should be is #21618 (Loading libc++ in ghci results in segfaults). As far as I am aware, this renders GHC 9.4 unusable on Windows for libraries that link against C++. (Or, at the very least, I haven't figured out a way to make it work.) Best, Ryan S.

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9.4.1 Final Call
by Matthew Pickering 05 Jul '22

05 Jul '22

Hello all, This is the final call for patches which need to be included in 9.4.1. The status of which I do not know the answer: * GHC 9.4 infinite loop in typechecker - #21530 (@simonpj, @rae) ? To my knowledge the remaining unfinished work list is: * Resolve static linking issues with text-2.0 - #21787 (Unresolved) (Matt/Ben/Zubin/Tamar/Andreww) * CAF reachability bug with -fprof-late - !7797 (WIP) (Andreas/Ben) * XMonad segfault - #21708 (WIP) (Ben/Andreas) * HIE File Fixes - !7888 (landing) (Zubin) * template-haskell-2.19.0.0 depends on filepath - !8516 (landing) (Matt) * Module loops and multiple home units leads to a panic - !8573 (nearly ready to land) (Matt) * extendMG leaks memory - #21816 (Zubin/Matt) To my knowledge, the following are not making it into 9.4.1.. but are not critical to revert: * Tidy up withDict and friends - #21568 Looking like a great release. Matt

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Howto build optimized with stack traces/9.2.3 build broken?
by Benjamin Maurer 03 Jul '22

03 Jul '22

Hey all, I'm trying to debug a segfault caused by my optimization. GHC only segfaults when compiled with -O2 and my flag, i.e., I used the "perf" flavour: > ./hadrian/build -j "stage1.*.ghc.hs.opts += -fregs-ssa" --flavour=perf However, I can't get a stack trace. [1] suggests I need a profiling build for that. So I tried: > ./hadrian/build -j "stage1.*.ghc.hs.opts += -fregs-ssa" --flavour=perf+debug_info+profiled_ghc+no_dynamic_ghc Unfortunately, I'm using GHC 9.2.1 from ghcup to bootstrap and this version doesn't come with profiling enabled base [2]. 8.10.7, which I have installed, can't compile ghc anymore (it seems). So I tried 9.2.3 from ghcup and that gives me the strangest errors. Basically, the compiler seems completely bricked. I installed 9.2.3, ran "hadrian/build clean", "./configure && ./boot" and the same line as above with both "default" and "perf" flavours. When I try to compile nofib/spectral/simple, I get: > /home/ben/Projekte/haskell/ghc/_build/stage1/bin/ghc -O2 Main.hs > [1 of 2] Compiling Main ( Main.hs, Main.o ) > Main.hs:1125:1: error: lexical error (UTF-8 decoding error) (Main.hs only has 1124 lines though, file was not modified, compiles fine with any other ghc version) But most programs I tried give me: > /home/ben/Projekte/haskell/ghc/_build/stage1/bin/ghc -O2 Main.hs > ghc: Unable to commit 283468890112 bytes of memory > ghc: Exiting. The system might be out of memory. Oh kay. I got 16GB RAM, 10 gig available. GHC 9.2.3 works fine. Is my flavour combination bad, or what is broken here? Any other (better) way to get an optimized build with all the debugging aids I can get? I heard GHC 9.2.2 is a broken release, or does anyone know whether it works on Linux x86_64 (and comes with profiling libs from ghcup) - maybe I can get a working version using that? I'd try, but creating a new build takes almost an hour and I have spent most of the day trying to solve this. I am puzzled and desearate to fix my bug and get a working compiler. Appreciate any help! Best Regards, Benjamin [1] https://gitlab.haskell.org/ghc/ghc/-/blob/master/hadrian/doc/debugging.md [2] https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/296

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RST Documentation Trick for reference links
by Matthew Pickering 01 Jul '22

01 Jul '22

Hello, I noticed myself writing things like: ``` and enable the eventlog using :rts-flag:`-l ⟨flags⟩`. ``` When in fact what I wanted was to create a link the eventlog options but render the link as just -l rather than -l <flags>.. but I thought I had to write the whole thing to get the linter to not complain. It turns out can achieve this goal using the following syntax: ``` and enable the eventlog using :rts-flag:`-l <-l ⟨flags⟩>`. ``` ie, include the thing you actually want to reference in angular brackets < > and the text you want to render before that. Yet another thing which has changed my life for good. Cheers, Matt

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Guide for testing hackage documentation upload
by Matthew Pickering 01 Jul '22

01 Jul '22

Hi all, In case anyone needs this in the future or is interested then I wrote a little guide about how to test the upload of hackage documentation locally. https://gitlab.haskell.org/ghc/ghc/-/wikis/testing-hackage-documentation Cheers, Matt

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