[cfe-dev] Clang and C++Ox : what I'm doing wrong

[Sebastian Redl]

On 08.10.2010, at 09:27, Jaonary Rabarisoa wrote:

> Hi all,
> 
> I trying build the following simple code that use a static const variable inside a class but I got an undefinend reference error :
> 
> #include <iostream>
> 
> using namespace std;
> 
> class Test
> {
>   public :
>     static const double value = 10.0;
> };
> This code produce the following warning and error at link time :
> 
> clang: warning: argument unused during compilation: '-cc1'
> /home/jrabarisoa/Sandbox/test_clang/main.cpp:27:25: warning: in-class initializer for static data member of type 'const double' is a
>       C++0x extension [-Wc++0x-extensions]

You're not actually compiling as C++0x.

>     static const double value = 10.0;
>                         ^       ~~~~
> 1 warning generated.
> Linking CXX executable test
> g++: unrecognized option '-cc1'
> CMakeFiles/test.dir/main.cpp.o: In function `main':
> /home/jrabarisoa/Sandbox/test_clang/main.cpp:(.text+0x7a): undefined reference to `Test::value'
> collect2: ld returned 1 exit status
> 
> What I've missed ?

Since you didn't compile as C++0x, I can't be sure if the same issue exists there, but C++03 requires a definition of static class members unless it's an integral constant whose lvalue is never needed. I don't know if C++0x extends this to all literal type constants. I wouldn't be surprised if Clang requires the definition anyway.

Sebastian