Re: musl-llvm-clang-libc++

[Szabolcs Nagy <nsz@port70.net>]

* Tomasz Sterna <tomek@xiaoka.com> [2015-01-06 15:31:43 +0100]:
> You might be interested to know, that I managed to build a
> musl + LLVM (clang, libc++) based, self hosted system.
> 
> The hardest part was to scrub libgcc and libstdc++ dependencies.
> Using instructions from Wiki[1] and hints from this list[2] and LLVM
> bugtracker[3] I finally managed to get a self-hosting system able to
> rebuild itself clean without any GCC help.

nice

> It requires a bit arm-twisting to LLVM compiler and libs, but it looks
> like it works just fine. The musl/libc++/clang++ env is able to build
> working libc++ and clang++, which I consider GoodEnough(TM) test case.

i ran http://repo.or.cz/w/libc-test.git on it and it turned up
some float bugs:

- musl's FLT_ROUND is wrong: it should reflect the current rounding mode
(i found this because clang float.h was used when comiling the tests
instead of musl's which may or may not be a problem)

- clang does not support c99 fenv and -frounding-math flag so fenv tests
are broken, but i didnt see incorrect results because of this

- long double is broken for some reason: strtod, and most long double
math functions give bad results in some cases, needs more investigation..


> 
> If you want to toy around with it you can install it directly from repo.
> 
> # mkdir /mnt/test	# I usually mount a btrfs subvolume here
> # apk.static --repository http://ftp.d-os.eu/latest/core --update-cache --allow-untrusted --root /mnt/test --initdb add dos-base dos-sdk libcxx-dev
> 
> It is based on great work of Alpine Linux.
> Still heavily work-in-progress and very rough on edges, but I think it
> may be very useful for people trying to get free of GNU libc, libstdc++
> and GCC bits, so I decided to share early.
> Also it is good to have some more eyes on as there is a lot of guesswork
> there.
> 
> The apk sources with required patches and some quick notes are on
> GitHub: https://github.com/D-os/aports/tree/master/core
> 
> 
> [1] http://wiki.musl-libc.org/wiki/BuildingLLVM
> [2] http://www.openwall.com/lists/musl/2014/04/22/2
> [3] http://llvm.org/bugs/show_bug.cgi?id=7276
> 
> -- 
> Tomasz Sterna                           :(){ :|:&};:
> Instant Messaging Consultant   Open Source Developer 
> http://abadcafe.pl/      http://xiaoka.com/portfolio
>