C++/C Code to have different execution block on M1 and Intel - c++

Question

I am writing a code for macOS application.
The application would be running on M1 based Macs as well as Intel based Macs also.
What would be the switch to differentiate M1 and Intel?
if (M1)
{
do something for M1
}
else if (Intel)
{
do something for Intel
}

Answer 1

I think, you can use __arm__ to detect arm architecture:
#ifdef __arm__
//do smth on arm (M1)
#else
//do smth on x86 (Intel)
#endif

Answer 2

I was just fooling around with this and found this reference for Objective-C from apple that seemed to work with clang for C++.
// Objective-C example
#include "TargetConditionals.h"
#if TARGET_OS_OSX
// Put CPU-independent macOS code here.
#if TARGET_CPU_ARM64
// Put 64-bit Apple silicon macOS code here.
#elif TARGET_CPU_X86_64
// Put 64-bit Intel macOS code here.
#endif
#elif TARGET_OS_MACCATALYST
// Put Mac Catalyst-specific code here.
#elif TARGET_OS_IOS
// Put iOS-specific code here.
#endif
https://developer.apple.com/documentation/apple-silicon/building-a-universal-macos-binary
I specifically checked to see if TARGET_CPU_ARM64 was defined in my header.
Hopefully this helps someone.

Answer 3

If you need a runtime check instead of compile time check, you can think of using something like below
#include <sys/sysctl.h>
#include <mach/machine.h>
int main(int argc, const char * argv[])
{
cpu_type_t type;
size_t size = sizeof(type);
sysctlbyname("hw.cputype", &type, &size, NULL, 0);
int procTranslated;
size = sizeof(procTranslated);
// Checks whether process is translated by Rosetta
sysctlbyname("sysctl.proc_translated", &procTranslated, &size, NULL, 0);
// Removes CPU_ARCH_ABI64 or CPU_ARCH_ABI64_32 encoded with the Type
cpu_type_t typeWithABIInfoRemoved = type & ~CPU_ARCH_MASK;
if (typeWithABIInfoRemoved == CPU_TYPE_X86)
{
if (procTranslated == 1)
{
cout << "ARM Processor (Running x86 application in Rosetta)";
}
else
{
cout << "Intel Processor";
}
}
else if (typeWithABIInfoRemoved == CPU_TYPE_ARM)
{
cout << "ARM Processor";
}
}