Error LNK2001 with variables inside namespace

Question

I have 2 files:

1. tier1.h

2. tier1.cpp

In tier1.h I have:

//code

namespace variab
{
  int x...; float tpl...; //etc
}

namespace universal
{
  using namespace variab;
  //some functions prototypes
}

In tier1.cpp there are the functions defined. Some of the functions are in imbricated namespaces, like: universal::extG::. These functions are using the variables found in variab namespace.

In the source file, where main is to be found, tier1.h is included.

When I try to compile the program, it gives me errors pointing to the variables found in variab namespace. The error is the same everywhere. This is how it looks:

error LNK2001: unresolved external symbol "int * variab::st" (?st@variab@@3PAHA)

Where is the problem?

Answer 1

In the header file you're declaring the variables in the namespace. You need to only declare them with the extern keyword:

namespace variab
{
    extern int x;
    extern float tpl;
    // etc...
}

Then in a source file you do the definition:

namespace variab
{
    int x;
    float tpl;
    // etc...
}