All 10 Preprocessor & Macros questions
More in Preprocessor & Macros
What is an include guard and why is it needed? What are predefined macros like __LINE__ and __FILE__? Why are function-like macros discouraged in modern C++? What are conditional compilation directives used for? What are the # (stringize) and ## (token paste) operators? How does #pragma once compare to traditional include guards? What are the dangers of macros affecting names and how do you mitigate them?
Advertisement
C++ › Preprocessor & Macros

What is the difference between a macro constant and a constexpr/const constant?

Intermediate

Answer

A #define constant is untyped preprocessor text substitution with no scope, no type checking, and no debug symbol. A const/constexpr constant is a typed, scoped variable known to the compiler and debugger, participating in overload resolution and type safety. Modern C++ strongly prefers constexpr/const over #define for constants.
#define MAX 100          // untyped text
constexpr int Max = 100;   // typed, scoped, debuggable
Real-world example Replacing #define constants with constexpr gives type safety and lets them appear in the debugger.

Common follow-ups: Why prefer constexpr over #define? | Do macros have scope?

Constexpr & Compile-Time Preprocessor & Macros Preprocessor & Macros
All 10 Preprocessor & Macros questions