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Date: Fri, 19 Nov 2021 15:00:55 -0500
From: Rich Felker <dalias@...c.org>
To: Matt Andrews <mattandrews@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: Why does musl require another libc to be built (noob
 question)

You dropped the list on your reply so I re-sent your mail to the list
on CC.

On Fri, Nov 19, 2021 at 10:16:30AM +1100, Matt Andrews wrote:
> So if there is no dependency on another libc, then the only ‘dependency’
> musl would have is some compiler runtime?

If the compiler generates calls to its own library functions as part
of implementing language constructs (e.g. 64-bit division, floating
point on softfloat archs, etc.) then you need this library code. This
is libgcc.a or compiler_rt.

> I see in the source there is a ‘crt’ folder. Is that musl’s compiler
> runtime?

No, these are the sources for the entry point object files linked into
every program as opposed to part of the library.


> On Fri, 19 Nov 2021 at 09:31, Matt Andrews <mattandrews@...il.com> wrote:
> 
> > Oh. I read somewhere that some syscalls like abort require an
> > implementation that is picked up from some other libc.
> >
> > On Fri, 19 Nov 2021 at 08:40, Rich Felker <dalias@...c.org> wrote:
> >
> >> On Fri, Nov 19, 2021 at 08:28:54AM +1100, Matt Andrews wrote:
> >> > Lately I’ve been trying to cross compile musl with clang. It’s been a
> >> > really interesting process and everyone on this list has been really
> >> > helpful.
> >> >
> >> > I hope this isn’t too much of a silly question, but there’s a missing
> >> piece
> >> > to my understanding of the standard library and that is why you need
> >> > another libc to build it. I assumed that it is a self contained thing,
> >> > everything else depends on it.
> >> >
> >> > I’m sure there are very good reasons for needing another standard
> >> library
> >> > to build musl, but I’m not sure what they are and if anyone could let me
> >> > know that would greatly appreciated.
> >>
> >> It doesn't and I'm not sure where you got that idea. Can you explain
> >> what you mean?
> >>
> >> Rich
> >>
> >

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