Comment #2 on issue 195 by jmccaskey: common.h should not have "using
namespace std;"
http://code.google.com/p/protobuf/issues/detail?id=195
Yes, although the using statement is inside your own namespace it appears
that at
least in Visual C++ 2005 the encapsulation is leaky and having used the
namespace can
affect other code in the global name space. Maybe this is a Visual C++
bug, it does
seem to be violating scope rules for the using directive somehow. Even if
it is
Visual C++ specific though, what if my application code wanted to use the
google::protobuf name space but not std? Having that also automatically
cause using
of std still seems undesirable.
Below is a simple test program that reproduces the issue directly just by
including
the common.h header. You'll notice I define a swap function directly in
the global
namespace, and it ends up causing ambiguity with the std::swap function.
If the
"using namespace std;" is removed from common.h this problem disappears.
The compilation errors will be:
1>Compiling...
1>test.cpp
1>c:\users\jmccaskey\documents\visual studio
2005\projects\test\test\test.cpp(21) :
error C2668: 'swap' : ambiguous call to overloaded function
1> c:\users\jmccaskey\documents\visual studio
2005\projects\test\test\test.cpp(8): could be 'void swap<int>(T &,T &)'
1> with
1> [
1> T=int
1> ]
1> c:\program files (x86)\microsoft visual studio
8\vc\include\utility(16): or
'void std::swap<int>(_Ty &,_Ty &)'
1> with
1> [
1> _Ty=int
1> ]
1> while trying to match the argument list '(int, int)'
// test.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "google/protobuf/stubs/common.h"
template< class T >
void swap( T &a, T &b )
{
T tmp = a;
a = b;
b = tmp;
}
int _tmain(int argc, _TCHAR* argv[])
{
int one = 1;
int two = 2;
swap( one, two );
return 0;
}
--
You received this message because you are subscribed to the Google Groups "Protocol
Buffers" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/protobuf?hl=en.
