dist/IO.xs remove a dTHX call

[bulk88]

• threaded perls without CPerlHost/iperlsys.h (ie all threaded unix perls) dont need a my_perl ptr, and don't assume all CCes have perfect LTO/LTCG and all OSes have a perfect designed bin image loader, to optimize away an unused my_perl var. This symbol crosses 2 separate TUs. ELF interposition, on paper, doesn't allow shifting over and dropping out args, but in real life, things are probably different. Write it correctly than assume optimizations will happen.

---

• This set of changes requires a perldelta entry, and it is included.
• This set of changes requires a perldelta entry, and I need help writing it.
• This set of changes does not require a perldelta entry.

[Leont]

These declarations should probably come after the definition of struct pollfd

[Leont]

This code should not even run on Mac. poll(2) seems to have been explicitly disabled because MacOS 10.4 broke poll(). 20 years ago, and no one ever looked at it again.

[mohawk2]

It's not compiling on MacOS:

In file included from poll.c:17:
./poll.h:37:28: warning: declaration of 'struct pollfd' will not be visible outside of this function [-Wvisibility]
   int Perl_my_poll(struct pollfd *, unsigned long, int);
                           ^
poll.c:48:1: error: conflicting types for 'Perl_my_poll'
Perl_my_poll(struct pollfd *fds, unsigned long nfds, int timeout)
^
./poll.h:37:8: note: previous declaration is here
   int Perl_my_poll(struct pollfd *, unsigned long, int);
       ^

[bulk88]

I'm gonna revise this commit and repush it and see if I can fix it for OSX in the CI cloud w/o personal access to an OSX SDK. I will note, in current blead version of the code, there is no static tag (needed for good citizen reasons). And that is intentional since there are 2 TUs and its out of scope for me to do that plastic surgery to get rid of TU # 2.

[bulk88]

pushed rev # 2

[tonycoz]

This is incomplete, poll.c doesn't define PERL_NO_GET_CONTEXT, so the call to select() compiles to:

    err = ((*((((PerlInterpreter *)Perl_get_context())->ISock)))->pSelect)((((PerlInterpreter *)Perl_get_context())->ISock), n+1, (char*)&rfd, (char*)&wfd, (char*)&efd, tbuf);

which I doubt is the result you wanted.

[bulk88]

This is incomplete, poll.c doesn't define PERL_NO_GET_CONTEXT

Good catch. That was a cherry pick or rebase git accident on my side at some point. The very 1st attempt (draft) had the PERL_NO_GET_CONTEXT line. The hunk from poll.c disappeared when the early WIP version of this commit got moved from a generic branch to this purpose-named branch for polishing and final submit.

On purpose, I am not going to overthink #if defined(PERL_IMPLICIT_SYS) vs any other possible substitute CPP macro test. I know Win32 is the only legit user of PERL_IMPLICIT_SYS and the only legit platform that will want the pTHX, but officially per the Perl C XS API, the feature test is #if defined(PERL_IMPLICIT_SYS) and nothing else. dist/IO/*.c.xs.h isn't the place to re-engineer any such build logic and it is a dual-life CPAN XS module on paper that must support ancient stable perls.

I am aware this PR opened a can of worms, of why on earth, Perl on OSX 15, needs to be emulating a basic POSIX syscall, but that topic is beyond scope for this PR. It will be someone elses PR and code, if they want to solve that topic. Just mentioning that OSX thing here in this PR for archive reasons if someone is researching or git blaming in the future.

pushed as rev # 3

[tonycoz]

I am aware this PR opened a can of worms, of why on earth, Perl on OSX 15, needs to be emulating a basic POSIX syscall, but that topic is beyond scope for this PR.

There's also WSAPoll(), but apparently that's also badly broken.