Date: Tue, 30 Jan 2024 11:12:16 -0800 From: Enji Cooper <yaneurabeya@gmail.com> To: Lexi Winter <lexi@le-fay.org> Cc: freebsd-arch@freebsd.org Subject: Re: improving C++ libc headers Message-ID: <7D5B040A-688E-47EA-8BF6-04AA18477399@gmail.com> In-Reply-To: <Zbj6DuTgT7i88Zkd@ilythia.eden.le-fay.org> References: <Zbj6DuTgT7i88Zkd@ilythia.eden.le-fay.org>
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> On Jan 30, 2024, at 05:31, Lexi Winter <lexi@le-fay.org> wrote:
>=20
> =EF=BB=BFhi list,
>=20
> i am considering working up a patch to improve C++ libc headers in FreeBSD=
.
>=20
> the problem with the current headers (which come from clang/libc++) is
> that this code compiles:
>=20
> ------
> #include <cstdlib>
> auto main() -> int {
> exit(0);
> }
> ------
>=20
> this should be a compile-time error, because <cstdio> does not declare
> ::exit[0]. however, it works because <cstdlib> is implemented like
> this:
>=20
> ------
> #include <stdlib.h> // exposes ::exit()
>=20
> namespace std {
> using ::exit;
> // ...
> }
> ------
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> i would like to replace this with an implementation that does this
> instead:
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> ------
> namespace std {
> extern "C" void exit(int);
> // ...
> }
> ------
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> i have done a very quick proof of concept for this and it does work;
> there are some more complicated edge cases, but nothing that can't be
> dealt with from what i can see.
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> but before i put any amount of significant effort into this, i'd like to
> check if this is something that is likely to be merged.
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> to address some potential objections:
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> - i don't believe this can be handled upstream in libc++, because some
> of these headers require knowledge of the implementation - <cstdio>
> needs to know about 'struct __sFILE', for example.
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> - "import std" should solve this properly, but there are a lot of
> implementation issues with this and it's not clear if/when it will
> ever be supported; in the mean time, the existing standard headers
> should behave correctly.
>=20
> [0] https://www.eel.is/c++draft/cstdlib.syn#header:%3Ccstdlib%3E
> [1] https://cgit.freebsd.org/src/tree/contrib/llvm-project/libcxx/include/=
cstdlib
Hi Lexi!
That=E2=80=99s an interesting proposal!
Given that this is a third-party library, I think it=E2=80=99s best to submi=
t this proposal and patches up to the LLVM project (there are some folks in t=
he FreeBSD project who are connected to LLVM, but arch is a wider distributi=
on of folks and might not overlap with those individuals). The proposal woul=
d be beneficial to multiple OSes=E2=80=94not just FreeBSD. Moreover, you mig=
ht be able to convince others in the LLVM project to work with you to achiev=
e the desired outcome sooner.
Thank you again for sharing and starting this discussion!
Cheers!
-Enji
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