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How do I define a constant expression with in a class?

spiffgq · 2002-11-21T15:09:04

My program was written using GCC and now I''m trying to port it to MSVC++ 6.0 (which is proving to be a big headache). I''ve managed to fix most of the errors, but there is one big problem that VC++ bitches about that GCC doesn''t care about: class MyClass { static const int MY_CONST = 1234; }; I get the errors : error C2258: illegal pure syntax, must be ''= 0'' error C2252: ''MY_CONST'' : pure specifier can only be specified for functions This can be fixed by putting the constant in the source file instead of the header file. But there is one case where I can''t move it: class OtherClass{ static const int MY_CONST; // this is assigned a value in the source file instead of here int arr[OtherClass::MY_CONST]; }; Now, if I try to compile it, error C2057: expected constant expression warning C4200: nonstandard extension used : zero-sized array in struct/union Is there some way to fix this knot? Thanks for your help.

General and Gameplay Programming Programming

Started by spiffgq November 18, 2002 03:33 PM

39 comments, last by spiffgq 21 years, 4 months ago

Xai

1,851

November 21, 2002 03:09 PM

risingdragon3 - don''t you get it yet ... you return the address of ANY of them ... usually the compiler will pick the first one, because it knows about it first, and stores its address in the symbol table when it computes it

the whole key is that we are talking about const objects, so the ONLY valid thing to do to an address of a const object is to compare it to another address, and read it''s value ... so any address will do ... this is NOT a theoretical only discussion, compilers actually DO this.

ChaosEngine - as i said, there IS support in C++ for const definitions in the class header in C++, IF AND ONLY IF they are of integer type ...

AND FOR VISUAL C++ 6.0 DO NOT DECLARE THEM STATIC, and you get no trouble ... because it is an integral constant, it makes no difference if it is static or not ... the compiler will NOT increade the size of your objects to hold const ints ... try it and see ...

How do I define a constant expression with in a class?

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How do I define a constant expression with in a class?

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