This talk was recorded at NDC TechTown in Kongsberg, Norway. #ndctechtown #ndcconferences #developer #softwaredeveloper    

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#cplusplus 

C++ is beautiful in the way that even the simplest things can be unexpectedly challenging and complex. You’d think that nothing could be easier than declaring a constant, right?

Choose the most suitable way to define it: a global variable, a local variable, or a static class data member. Maybe a template. Set the right linkage and storage duration. Use some combination of specifiers like static, inline, and constexpr for that. Maybe use extern in some cases. How does it play along with modules by the way?..

If all of this is obvious to you — congratulations! That’s impressive. But if this whole zoo makes your head spin a bit, let’s try to untangle it together.

NDC Conferences

A comprehensive guide to declaring constants in C++ covering local and global constants, storage duration, linkage types, and the use of const, constexpr, static, inline, and extern keywords. Explores how different specifiers affect binary size, initialization, cache usage, and ODR violations. Includes detailed assembly analysis showing optimization impacts, discusses anonymous namespaces for internal linkage, weak linkage for header files, and introduces C++20 modules with their different linkage semantics. Provides practical guidelines for each scenario with compiler explorer examples.

How to declare a constant in C++ - Mikhail Matrosov - NDC TechTown 2025