Thank you Jonathan and Tony, Fortunately, the class in which I am using this construct is templatized so the initializations as you (Tony) suggested are fine appearing just below the class. If it weren't a templatized class, doing so would produce multiply defined symbol errors. I suppose the only way around that is to have an implementation file which requires a library be built, etc. yes? (bummer) Thanks, John Jonathan Wakely wrote:
On Fri, Feb 11, 2005 at 02:23:42AM +0000, Tony Han Bao wrote:
Hi John,
From the standard:
9.4.2 Static data members
4 If a static data member is of const integral or const enumeration type, its declaration in the class definition can specify a constant-initializer which shall be an integral constant expression (5.19). In that case, the member can appear in integral constant expressions within its scope. The member shall still be defined in a namespace scope if it is used in the program and the namespace scope definition shall not contain an initializer.
so adding the line
const short S::l1;
solves the problem.
Note this is documented here: http://gcc.gnu.org/onlinedocs/gcc/Static-Definitions.html#Static-Definitions
But I still don't understand neither why passing by value doesn't cause the error.
Because when passing by value S::l1 is only used as an integral constant expression, to initialise a variable. Passing by reference is similar to taking its address, which requires it to *have* and address, which requires if to have storage, so it must have been defined somewhere.
jon
On 11 Feb 2005, at 01:03, John Eddy wrote:
The following bit of code gives me an undefined symbol (l1) when using gcc 3.2.2-5.8. Is there something wrong with the code or is there a bug in the compiler or a setting I don't know about, etc?
struct S { static const short l1 = 10; };
void go(const short& l) {}; // causes undefined symbol l1
int main(int argc, char* argv[]) { go(S::l1); return 0; }
If I do normal, non-in-class-initialization, the problem doesn't appear nor does it appear if I accept the short by value in go.