Yes, it is required that static data members must be defined in exactly one translation unit. Please see: http://gcc.gnu.org/onlinedocs/gcc/Static-Definitions.html#Static-Definitions http://www.parashift.com/c++-faq-lite/ctors.html#faq-10.11 Regards, Ryan Mansfield -----Original Message----- From: gcc-help-owner@xxxxxxxxxxx [mailto:gcc-help-owner@xxxxxxxxxxx] On Behalf Of John Ratliff Sent: Sunday, October 16, 2005 3:36 AM To: gcc-help@xxxxxxxxxxx Subject: C++ static integer class constants... A few days ago, I was writing a program that had some constants. They were all defined in a class and were static constant integers, something like class foo { public: static const int X = 5; static const int Y = 10; static const int Z = 15; }; When I would compile my program in Windows XP with mingw g++ 3.4.2, I would have no problems. However, when I went to Linux, where I have g++ 3.3.5 (or possibly 3.3.6, but I think it's 3.3.5), the linker would complain about unresolved symbols. If I were to define the static variable in my implementation file, the linker would find the variables and go on its merry way. In other words, I could solve the problem by doing this: const int foo::X; const int foo::Y; const int foo::Z; I didn't even need to declare a value here. It took the value from the class-def. Is this correct behavior? I thought static constant integers could be defined completely within the class, because they are simply type-safe constants that need no storage space. It seems like it might have been wrong since in Windows I had g++ 3.4.2 and in Linux I had g++ 3.3.5, but I wasn't sure. In Bruce Eckel's "Thinking in C++", he states that "In older versions of C++, static const was not supported inside classes." I don't generally think of g++ 3.3.x as an old compiler, but maybe it is just old enough not to support this? Thanks, --John Ratliff
