Re: Musl git 0d......455eee8 and recent compilers

[Rich Felker <dalias@aerifal.cx>]

On Mon, Jun 06, 2011 at 10:48:08AM +0200, Igmar Palsenberg wrote:
> Hi,

Hi! Thanks for the reports.

> I was using Musle as a test for investigating a (completely
> unrelated) clang-analyser problem, and I've stumbled upon a couple
> of issues
> 
> 1) The struct dirent in include/dirent.h uses a 1 byte array for
> d_name. In reality, it's larger : We allocate more space than the
> struct. Since muscle requires a C99 compiler anyway, what's keeping
> use from using d_name[0] or d_name[] ? If a C89 compiler includes
> dirent.h, we're screwed anyway :). That will probably silence GCC
> 4.5 and clang, and severely reduce the warnings it gives in similar
> cases.

While musl requires a C99 compiler, my intent was to minimize breakage
when building programs against it using a lesser compiler. This could
probably just be changed though. I think the time of caring about
compilers that don't support [] is past..

> 2) The NULL pointer dereference in src/time/__asctime.c won't work
> with clang : It removes it. I suggest using either __builtin_trap()
> or an abort(). If you get to that point, you're in trouble anyway.

The best fix is adding volatile. __builtin_trap is compiler-specific
and calling abort will pull on bloat for no reason. (Note that raise
is actually a rather heavy function due to Linux not directly
supporting the correct POSIX semantics with regard to threads, and
having to hack it to be async-signal-safe from userspace...)

> 3) Clang does't seem to grasp the weak_alias thingy. It need to
> check if those parts actually are correct

Does it really not support making non-static aliases for static
functions? If so that's a major pain that will bloat the symbol table.
You can't just remove static though; the functions from which static
is removed will have to be renamed so as not to use reserved external
names.

> 4) Is there a muscl testsuite somewhere ?

A partial one:

git://git.etalabs.net/libc-testsuite

That's mostly quick examples I wrote just to make sure things were
basically working while writing musl; it's not exhaustive. Luka is
working on a much more extensive set of tests as a GSoC project.

Rich