extern const array does not link

Question

Possible Duplicate:
Why does const imply internal linkage in C++, when it doesn’t in C?

If I have the following:

a.cpp:

const int ArrayOfInts[] = {1, 2, 3, 4, 5};

b.cpp:

extern const int ArrayOfInts[];

void SomeFunc()
{
    int a = ArrayOfInts[0];
}

The linker complains that ArrayOfInts is unresolved from b.obj. Removing the const qualifier makes the link succeed. Any ideas why this fails?

Thanks.

David Schwartz · Accepted Answer · 2012-11-14T12:46:25.193

0

When the compiler compiles b.cpp, for all it knows, the value of ArrayOfInts[0] could be anything. So it's not a compile-time constant. In C++, constants at file scope are compile-time constants by default.

edited Nov 14 '12 at 12:46

answered Nov 14 '12 at 12:41

David Schwartz

179,497
17
214
278

1

You can make a constant at file scope with external linkage by declaring it `extern const`. – interjay Nov 14 '12 at 12:45
I'll add "by default" to the end of my answer. – David Schwartz Nov 14 '12 at 12:46
1

"In C++, constants at file scope are compile-time constants by default." - thought this only applied to simple integer types. Thanks for clarifying. – Badder Nov 14 '12 at 12:49

extern const array does not link

1 Answers1