Why preprocessor #define macros are error-prone and what to replace them with:

• Problem: Macros ignore scope, pollute global namespace, cause multiple evaluation side-effects (#define SQUARE(x) (x*x) with SQUARE(i++)), and produce cryptic compiler errors.

Modern C++ Replacements:

• Constants: constexpr int MaxRetries = 5;
• Global flags: inline constexpr std::string_view Version = "2.4.0";
• Utility functions: template<typename T> constexpr T Square(T x) { return x * x; }
• Compile-time conditions: if constexpr (sizeof(T) == 8) instead of #ifdef _WIN64.

Macros should be restricted strictly to header guards, conditional feature platform detection, and specialized stringification #x macros.

Everything else can and should be expressed using type-safe Modern C++ constructs.