I have been reading Signal Handler in a separate pthread using timer_create, and I decided to try implementing a C example for a periodic timer function based on the discussion there, and compiling it under MINGW64 for Windows.
It turns out, while MINGW64 can indeed emulate some aspects of POSIX under Windows, timer_create and sigevent are not part of that (/mingw64/include/signal.h does not contain declaration for sigevent - while MSYS2 /usr/include/signal.h, via /usr/include/sys/signal.h, does) - I get these errors:
test.c:153:1: error: unknown type name 'timer_t'; did you mean 'time_t'?
553 | timer_t timerId = 0;
| ^~~~~~~
| time_t
test.c: In function 'init_timer':
test.c:160:10: error: variable 'sev' has initializer but incomplete type
560 | struct sigevent sev = { 0 };
| ^~~~~~~~
test.c:160:27: warning: excess elements in struct initializer
560 | struct sigevent sev = { 0 };
| ^
test.c:160:27: note: (near initialization for 'sev')
test.c:160:19: error: storage size of 'sev' isn't known
560 | struct sigevent sev = { 0 };
| ^~~
test.c:170:22: error: 'SIGEV_THREAD' undeclared (first use in this function)
570 | sev.sigev_notify = SIGEV_THREAD;
| ^~~~~~~~~~~~
test.c:170:22: note: each undeclared identifier is reported only once for each function it appears in
test.c:174:9: warning: implicit declaration of function 'timer_create'; did you mean 'timerclear'? [-Wimplicit-function-declaration]
574 | res = timer_create(CLOCK_REALTIME, &sev, &timerId);
| ^~~~~~~~~~~~
| timerclear
test.c:180:9: warning: implicit declaration of function 'timer_settime'; did you mean 'timeGetTime'? [-Wimplicit-function-declaration]
580 | res = timer_settime(timerId, 0, &its, NULL);
| ^~~~~~~~~~~~~
| timeGetTime
test.c:160:19: warning: unused variable 'sev' [-Wunused-variable]
560 | struct sigevent sev = { 0 };
So, what I want to achieve, is a periodic timer callback of a function at a period of 10 ms (as tight as possible (*)), with C code that can compile with gcc under both MINGW64 and Linux.
Is it possible to achieve this - and if so, how? (maybe there is a library that facilitates this?)
(*) - in my experiments with MINGW64 builds on Windows 10, I've seen that nanosleep(&ts, &ts); in a while loop in main() with timestamp printouts, -- where ts = {.tv_sec = 0, .tv_nsec = 500 * 1000000} describes an interval of half a second, -- can measure anywhere between 505 and 520 ms; so I'm not sure how "tight" of a 10 ms period will be achievable - but I'd still love to know about options to implement a cross-platform periodic timer, even with a poorer timer resolution ...
