Re: [musl] add loongarch64 port v6.

[Szabolcs Nagy <nsz@port70.net>]

* 王洪亮 <wanghongliang@loongson.cn> [2023-04-04 17:46:36 +0800]:
> 在 2023/4/3 下午11:44, Szabolcs Nagy 写道:
> > i was asking because of this glibc patch:
> > https://sourceware.org/pipermail/libc-alpha/2023-April/146897.html
> > 
> > i dont understand that change (loongarch is in glibc since 2.36 release).
> 
> Based on the v6 patch,I Modified the member names of struct sigcontext to
> maintain
> consistency with kernel and glibc. As shown in

(1) if _XOPEN_SOURCE && !_GNU_SOURCE && !_BSD_SOURCE mcontext_t fields
need not be accessible and must be in the impl reserved namespace
(no glibc or linux api compat requirement, only posix namespace req).

(2) otherwise musl mcontext_t fields must match glibc.
(ucontext and mcontext_t must use the same api across libcs).

i think it does not matter if the fields are different from the linux
uapi sigcontext fields. glibc used to include linux asm/sigcontext.h
to define mcontext_t so the fields were the same, but that polluted
the namespace and got fixed a while ago:
https://sourceware.org/bugzilla/show_bug.cgi?id=21457
since then mcontext_t is not the same as struct sigcontext, but
even before that they should not have been used interchangably
in c apis (the c abi must match though).

so i would not change the glibc code to match linux. and update the
musl patch to match current glibc api. the only wart i see is that
all targets currently have an uc_flags field in ucontext, loongarch
has an __uc_flags, but i think that's fine if there is no portable
use of this field. you may want to look into that, but it can be
fixed with a #define uc_flags __uc_flags if needed.

the glibc loongarch maintainers can break their api (and c++ abi) if
they wish to make it consistent with linux uapi, but i don't think
that's very useful. i'd wait for the glibc patch to be resolved and
fix musl patches accordingly. the v6 patches currently violate both
(1) and (2) requirements.