extern const array does not link [duplicate]

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 · 2012-11-14 12:46:25Z

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, 2012 at 12:46

answered Nov 14, 2012 at 12:41

David Schwartz

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3 Comments

interjay Over a year ago

You can make a constant at file scope with external linkage by declaring it extern const.

David Schwartz Over a year ago

I'll add "by default" to the end of my answer.

Badder Over a year ago

"In C++, constants at file scope are compile-time constants by default." - thought this only applied to simple integer types. Thanks for clarifying.

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