[musl] Why does musl require another libc to be built (noob question)

[musl] Why does musl require another libc to be built (noob question)

[Matt Andrews]

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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.

Thanks

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Re: [musl] Why does musl require another libc to be built (noob question)

[Rich Felker]

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

Re: [musl] Why does musl require another libc to be built (noob question)

[Matt Andrews]

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So if there is no dependency on another libc, then the only ‘dependency’
musl would have is some compiler runtime?

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

On Fri, 19 Nov 2021 at 09:31, Matt Andrews <mattandrews@gmail.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@libc.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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Re: [musl] Why does musl require another libc to be built (noob question)

[Rich Felker]

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@gmail.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@libc.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
> >>
> >