How Can CPU Architecture Be Reliably Detected at Compile-Time?

Detecting CPU Architecture at Compile-Time

Challenge:

Determining the target CPU architecture during compilation can be a challenge due to the varying non-standard preprocessor definitions employed by different compilers. This presents the need for a reliable and consistent method to detect the architecture.

Reliable Detection:

While there is no universally established standard for detecting CPU architecture at compile-time, the most reliable approach is to leverage the following compiler-specific definitions:

• MSVC: _M_X64 for 64-bit architectures, _M_IX86 for 32-bit architectures
• GCC: __i386__ for x86_32, __x86_64__ for x86_64
• Clang: Similar to GCC, with additional definitions for other architectures

Comprehensive Header:

For a centralized way to handle architecture detection, consider utilizing a header file that encompasses all relevant definitions. Such a header could provide the following functionality:

#ifdef _M_X64
#define CPU_ARCH "x86_64"
#elif defined(__i386__)
#define CPU_ARCH "x86_32"
...
#else
#define CPU_ARCH "UNKNOWN"
#endif

By incorporating this header into your code, you can easily check the CPU_ARCH value to determine the target architecture.

Custom Detection Example:

For more detailed architecture detection, consider the following code snippet:

extern "C" {
    const char *getBuild() {
        #if defined(__x86_64__) || defined(_M_X64)
        return "x86_64";
        ...
        #else
        return "UNKNOWN";
        #endif
    }
}

This function provides a broad detection capability, covering x86, ARM, MIPS, PowerPC, and other architectures.

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