Hey! I had to start GSoC on sunday last week due to school, and I didn’t
\nthink that I’d write a weekly report for the first week but I decided to
\ndo it anyways.<\/p>\n
My plan for week 1 was:
\n>This week I will set up a LLVM toolchain and sysroot for compiling
\n>programs targeting LLVM libc. I will also start setting up a
\n>\u201cllvm-libc\/Linux from Scratch\u201d chroot.<\/p>\n
Because I played with LLVM libc before last week I had already completed this
\ngoal. Going forward I will only work in the sysroot until setting up
\ncrossdev because it’s simple and gives me everything I need to fix
\ndependencies like Python.<\/p>\n
This far the project has been going pretty smooth, but I’ve also ran
\ninto some issues which I will comment on.<\/p>\n
The first issue was regarding SSP when setting up the LLVM
\ntoolchain. LLVM libc currently does not support stack smashing
\nprotection, and somehow compiled binaries automatically wants it if the
\ntoolchain was built with SSP enabled, even when compiling with
\n-fno-stack-protector. Probably this has something to do with internal
\nlibraries getting built with it. I spent quite a bit of time on this
\nbecause I forgot CXXFLAGS was a thing and only set CFLAGS, thinking that
\nsomething else was causing it :). Why this works out of the box on some
\nother distributions, hence not in setup docs, is because Gentoo enables
\nSSP in the clang config files.<\/p>\n
(See:
\nhttps:\/\/blogs.gentoo.org\/mgorny\/2022\/10\/07\/clang-in-gentoo-now-sets-default-runtimes-via-config-file\/)<\/p>\n
I then moved on to work on Python. When I talked with LLVM libc
\ndevelopers about this project they told me that the biggest obstacle for
\nPython would be the missing libm functions, so I decided to use Julia’s
\nopenlibm instead of the built in one.<\/p>\n
> I\u2019d guess that python wouldn\u2019t quite work yet since we don\u2019t have all
\n> of the double precision math functions yet, though you might be able
\n> to fudge it by creating entrypoints that just call the single
\n> precision versions.<\/p>\n
Openlibm just compiled and worked
\nout of the box with Python by configuring with
\n–with-libm=*libopenlibm.a*, and then substituting math.h for
\nopenlibm_math.h.<\/p>\n
Next week I will mostly work on Python, because libm isn’t the only
\nissue. Things like fileno, wide strings, pthread_cond are used in Python
\nand is not in LLVM libc yet. posixsource.c is particularly annoying.
\nYes, I have a time machine.<\/p>\n
—
\ncatcream<\/p>\n","protected":false},"excerpt":{"rendered":"
Hey! I had to start GSoC on sunday last week due to school, and I didn’t think that I’d write a weekly report for the first week but I decided to do it anyways. My plan for week 1 was: … Continue reading