spring/spring — comment on commit 65954ac28979a5995a4d61ed3f714257a341eced
File:  line 0
By tvo:

According to and the error might be expected in a strictly c++03 conforming compiler.

TL;DR: in C++03 it was accidentally specified that static const only needs a definition if used outside a constant expression. Given the definition of constant expression, that means it can only be used as array size or in the calculation of another const value.

Most compilers supposedly interpret the standard less strict, and require a definition only when you *take the address of such a constant*.
Now here is the clue: `NUM_TEMP_QUADS` is used as argument to `std::max`, which takes `const T&` as argument. So unless inlined, which doesn't happen in debug mode, it takes the address of the constant. So a definition is required here. Or a workaround, which I'll try in 2 sec.