cpuinfo_get_current_core() return NULL on mac (intel chip)

[zchrissirhcz]

• OS: macOSX 12.4

(base) ➜  cpuinfo git:(master) uname -a
Darwin ZZ-MBP.local 21.5.0 Darwin Kernel Version 21.5.0: Tue Apr 26 21:08:22 PDT 2022; root:xnu-8020.121.3~4/RELEASE_X86_64 x86_64

• cpuinfo commit:

  * 5e63739 2022-07-18 | Add bazel support for iOS arm64 simulator (#105) (HEAD -> master, origin/master, origin/HEAD) [Keith 
   Smiley]
  

• Reproduce

#include <stdio.h>
#include "cpuinfo.h"

int main()
{
    cpuinfo_initialize();

    const cpuinfo_core* core = cpuinfo_get_current_core();
    printf("core is %p\n", core);

    cpuinfo_deinitialize();

    return 0;
}

• Expected behaviour
  The print value of core should be not "0x0"
• The actual output

core is 0x0

[Jianhua-Cui]

From the source code, it can be observed that this API is only valid for operating systems based on the Linux kernel:

const struct cpuinfo_core* CPUINFO_ABI cpuinfo_get_current_core(void) {
	if CPUINFO_UNLIKELY (!cpuinfo_is_initialized) {
		cpuinfo_log_fatal("cpuinfo_get_%s called before cpuinfo is initialized", "current_core");
	}
#ifdef __linux__
	/* Initializing this variable silences a MemorySanitizer error. */
	unsigned cpu = 0;
	if CPUINFO_UNLIKELY (syscall(__NR_getcpu, &cpu, NULL, NULL) != 0) {
		return 0;
	}
	if CPUINFO_UNLIKELY ((uint32_t)cpu >= cpuinfo_linux_cpu_max) {
		return 0;
	}
	return cpuinfo_linux_cpu_to_core_map[cpu];
#else
	return NULL;
#endif
}

I think the key issue is that the macOS system doesn't provide a system call / API that allows us to query which CPU core the current thread is running on.

So I don't think this is a bug.