Re: [musl] MUSL ignores__attribute__((constructor(priority))) ?

[Harald Welte <laforge@gnumonks.org>]

Hi Rich,

On Thu, May 21, 2020 at 05:49:48PM -0400, Rich Felker wrote:
> > According to the OpenWRT build I have been provided by a 3rd party, it's
> > using musl-1-1.23.
> 
> Can you confirm this to make sure we're not debugging an issue that's
> long since fixed? Run /lib/ld-musl-armhf.so.1 as a command and it will
> print its version.

*sigh*. It was 1.1.20.  This specific (vendor) OpenWRT tree was broken in that
it used the 1.1.20 source code but called the generated packages and
path names 1.1.23 :/

After updating the sources to actual 1.1.23, the constructor order is
correct and I can run the unmodified libraries + application just like
on glibc.

Sorry for the noise then.  Normally if something is named 1.1.23 you
assume it also is 1.1.23 inside...

> FWIW the only standards that musl purports to actually adhere to are
> C, POSIX, and IEEE 754 (as referenced by C Annex F). While ELF is the
> binary format used and we aim to use it in compatible ways so as not
> to be gratuitously breaking, there are a lot of details that do not
> match historical SysV behavior (this is also true on glibc to a lesser
> extent), e.g. historical RPATH vs RUNPATH difference, LD_* vars, etc.

Does that explain why trying to LD_PRELOAD libtalloc didn't fix the
ordering either?  It was one humble attempt at manually overriding the
order (on 1.1.20).

> I only bring this up because "historical SysV documents say you have
> to do things this way" is not *automatically* a compelling argument
> for what musl should do, just one ingredient for consideration.

I would argue the compelling argument is to ensure applications (of
which probably 99% or at least 90% are written and tested with glibc)
will work ideally without porting, or without significant porting effort
and/or without subtle or not-so-subtle bugs [not claiming you did so,
just arguing hypothetically].  But then, this is just the library user
perspective of course, and everyone can run their project the way they
want.

Thanks again.

Regards,
	Harald
-- 
- Harald Welte <laforge@gnumonks.org>           http://laforge.gnumonks.org/
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