Question

See subject. What were they thinking?

UPDATE: Changed from “static” to “internal linkage” to save confusion.

To give an example… Putting the following in a file:

const int var_a = 1;
int var_b = 1;

…and compiling with g++ -c test.cpp only exports var_b.

Answer 1

I believe you mean

Why does const imply internal linkage in C++

It’s true that if you declare a const object at namespace scope, then it has internal linkage.

Appendix C (C++11, C.1.2) gives the rationale

Change: A name of file scope that is explicitly declared const, and not explicitly declared extern, has internal linkage, while in C it would have external linkage

Rationale: Because const objects can be used as compile-time values in C++, this feature urges programmers to provide explicit initializer values for each const. This feature allows the user to put const objects in header files that are included in many compilation units.