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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: best approach for multithreading (?)
Date: Sat, 7 Dec 2024 20:36:24 -0800
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On 12/7/2024 7:49 PM, Kaz Kylheku wrote:
> On 2024-12-07, James Kuyper <jameskuyper@alumni.caltech.edu> wrote:
>> On 12/6/24 11:10, Scott Lurndal wrote:
>>> Kaz Kylheku <643-408-1753@kylheku.com> writes:
>>>> On 2024-12-06, James Kuyper <jameskuyper@alumni.caltech.edu> wrote:
>> ...
>>>>> C <threads.h> can be implemented as a thin wrapper over POSIX threads.
>>>>> The waste is relatively negligible. The differences, were intended to
>>>>> allow <threads.h> to also be implemented on non-POSIX systems as
>>>>> wrappers for whatever the native threading system was.
>>>>
>>>> Generally speaking, you can have a function called pthread_create on
>>>> non-POSIX systems, and a header <pthread.h>.
>>>
>>> There are certain requirements of a posix threads implementation that
>>> might be impossible for a non-POSIX system to implement efficiently;
>>> windows, for example, doesn't support signals.
>>
>> My words above not-withstanding, I am not in any sense an expert on any
>> kind of threading, nor of Windows. What does POSIX require of threads
>> with regards to signals?
> 
> Off the top of my head, the highlights:
> 
> - threads have their own signal masks, inherited from the creator which
>    calls pthtead_create.
> - signal masks can be manipulated so that a given signal will be
>    handled in the context of a desired thread.
> - sigwait (and several other functions) can be used by a thread to
>    wait for one or more signals, allowing signals to be process
>    synchronously, somewhat like message passing.
> 

Semaphores are sig safe, so to speak. It's been a while:

https://www.man7.org/linux/man-pages/man3/sem_post.3.html

should be sig safe? Or, am I wrong here Kaz?