Global array defined twice but still compiling?

Question

In a.h, I created an array without the extern keyword by mistake which should result in a tentative definition

a.h:

    MyStruct myArrayOfStructs [];

This array is then defined in a.cpp

a.cpp:

MyStruct myArrayOfStructs[CONSTANT];

This surprisingly compiled.

Why did the compiler not complain about redefinition?

Answer 1

That is perfectly valid. The first (.h) says there exists an array somewhere, but does not instantiate it.

The second allocates it.