P
Pep
Namespaces still confuse me when I try to get clever 
Can I do the following
// file1.h
#ifndef __NS1_H__
#define __NS1_H__
namespace ns1
{
some base class
}
#endif // __NS1_H__
// file file1.cc
#include <file1.h>
implementation of ns1:: classes defined in file1.h
// file2.h
#ifndef __NS2_H__
#define __NS2_H__
#include <file1.h>
namespace ns1
{
some derived class
}
#endif // __NS2_H__
// file2.cc
#include <file2.h>
implementation of ns1:: classes defined in file2.h
then compile file1.cc and file2.cc in to a library called libns1.a
file1.h defines a base class that is used in a derived class defined
in file2.h , so I obviously need to include file1.h in to file2.h.
The reason I have both the base and derived classes in the same
namespace is that later in the project lifetime there will be other
classes derived from the base class in file1.h and the functionality
that the collection of derived classes provide is considered to be a
unique module within the business model, so from a development point
of view it would be ideal if all derived classes sit within the same
namespace. It does not feel right to have to define a new namespace
for each derived class.
I do not want to put the base class and all derived class definitions
in the same header file as that means that everything will need to be
recompiled each time a new derived class is defined. In our already
lengthy build process, adding more time by haveing to rebuild all
derived class implementation files just because we added a new one is
not desired.
I tried something like this and whilst the library libns1.a is built
okay (I say this because there are no errors in the build process) I
get problems when I try to use the library, as follows
//file main.cc
#include <file2.h>
int main(int argc, char** argv)
{
// do something
}
When I compile main.cc and link against libns1.a, I get the following
error
libns1.a(file2.o) multiple definition of `namespaces' testns1.o.data
+0x0): first defined here
So where am I going wrong, is it that it is simply not possible to
extend the definition of a namespace across header files?
I am building this on a linux o/s with g++ 3.3.6
TIA,
Pete
Can I do the following
// file1.h
#ifndef __NS1_H__
#define __NS1_H__
namespace ns1
{
some base class
}
#endif // __NS1_H__
// file file1.cc
#include <file1.h>
implementation of ns1:: classes defined in file1.h
// file2.h
#ifndef __NS2_H__
#define __NS2_H__
#include <file1.h>
namespace ns1
{
some derived class
}
#endif // __NS2_H__
// file2.cc
#include <file2.h>
implementation of ns1:: classes defined in file2.h
then compile file1.cc and file2.cc in to a library called libns1.a
file1.h defines a base class that is used in a derived class defined
in file2.h , so I obviously need to include file1.h in to file2.h.
The reason I have both the base and derived classes in the same
namespace is that later in the project lifetime there will be other
classes derived from the base class in file1.h and the functionality
that the collection of derived classes provide is considered to be a
unique module within the business model, so from a development point
of view it would be ideal if all derived classes sit within the same
namespace. It does not feel right to have to define a new namespace
for each derived class.
I do not want to put the base class and all derived class definitions
in the same header file as that means that everything will need to be
recompiled each time a new derived class is defined. In our already
lengthy build process, adding more time by haveing to rebuild all
derived class implementation files just because we added a new one is
not desired.
I tried something like this and whilst the library libns1.a is built
okay (I say this because there are no errors in the build process) I
get problems when I try to use the library, as follows
//file main.cc
#include <file2.h>
int main(int argc, char** argv)
{
// do something
}
When I compile main.cc and link against libns1.a, I get the following
error
libns1.a(file2.o) multiple definition of `namespaces' testns1.o
.data+0x0): first defined here
So where am I going wrong, is it that it is simply not possible to
extend the definition of a namespace across header files?
I am building this on a linux o/s with g++ 3.3.6
TIA,
Pete