Weekly report 2, LLVM libc

Hi! This week I’ve continued my work on getting Python to run. It has
mostly involved defining a lot of missing functions and types for

These are mostly taken from musl libc, but some things are also just
implemented using a no op.

In LLVM libc there are currenly some headers without all the needed
declarations available. That will make “HAVE_*_H” configuration tests
pass, but then fail later. For some of these cases I simply did
‘#undef’ and hoped the functionality wasn’t needed.

My current plan is to just get Python to build, and then go back to
fix things properly, within reason.

I also found a bug in LLVM libc where the TableGen specifications for
truncate and ftruncate had mixed up argument types. Because the
libc headers are generated from these specifications, the unistd.h
header had incorrect declarations for these functions. As this did not
add any new things, and was easy to implement, I got it committed into
upstream LLVM instead of keeping it locally like the other fixes. Sam
suggested that if I get stuck on something and want to do something
else for I while I could go through the spec files and look for errors
similar to this (truncate commit on phabricator).

At the end of the week I went back to fix an error I got while setting
up LLVM libc, that being an error related to PRId64 format string. Sam
suggested that I could use this to learn how to use cvise, which I
will do next week.

Next week I aim to be finished with Python, and in that case I’ll
continue with getting Crossdev to work with LLVM by making it able to
compile compiler-rt for non-host triples.

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