Use sysconf(_SC_NPROCESSORS_CONF) in PAL and GC ONLY on ARM and ARM64

[echesakov]

This PR limits usage of sysconf(_SC_NPROCESSORS_CONF) only to ARM and ARM64 (see #18053 (comment)) in the same way it is done in Release/2.1 #18055

@janvorli PTAL
/cc @RussKeldorph

[echesakov]

@dotnet-bot test OSX10.12 x64 Checked Innerloop Build and Test
@dotnet-bot test Ubuntu arm Cross Checked corefx_baseline Build and Test

[janvorli]

A nit - instead of defining the macro and its string version, you can define a stringification macro that will make the conversion automatically:

#define STRINGIFY1(s) #s
#define STRINGIFY(s) STRINGIFY1(s)

Then you can write the assert like this:

ASSERT("sysconf failed for %s (%d)\n", STRINGIFY(SYSCONF_GET_NUMPROCS), errno); 

[echesakov]

Actually, I though about this once but I could not justify doing stringification instead of hard-coding names of the variables.

Unfortunately, doing stringification your way would not work for this example

#define _SC_NPROCESSORS_CONF 57
#define _SC_NPROCESSORS_ONLN 58

#define SYSCONF_GET_NUMPROCS       _SC_NPROCESSORS_CONF 
//#define SYSCONF_GET_NUMPROCS       _SC_NPROCESSORS_ONLN

#define STRINGIFY1(s) #s
#define STRINGIFY(s) STRINGIFY1(s)

int main()
{
    printf("STRINGIFY(SYSCONF_GET_NUMPROCS) is %s\n", STRINGIFY(SYSCONF_GET_NUMPROCS)); // Output: STRINGIFY(SYSCONF_GET_NUMPROCS) is 57
    return 0;
}

This is how SC_NPROCESSORS_CONF is defined in FreeBSD https://github.com/freebsd/freebsd/blob/06362ad468fc11671364e34ed413ea9c19d858f1/include/unistd.h#L292

[janvorli]

Ok, thanks, forget about it then.

[echesakov]

It seems that failure in Ubuntu arm Cross Checked corefx_baseline Build and Test happened before. I opened a corresponding issue #18295