VC + + Export functions with namespaces

• • Problem phenomenon
  • Cause analysis
  • Solutions

1 Problem phenomena

Exports functions and classes that have namespaces. The source code is as follows:

Header file MiniMFC.h

namespace MiniMFC{    void f();    class __declspec(dllexport) MyClass    {    public:        void Mf();    };}

Implementing File MiniMFC.cpp

#include "stdafx.h"#include <iostream>usingnamespacestd;#include "MiniMFC.h"usingnamespace MiniMFC;void MyClass::Mf(){    cout"I‘m MiniMFC::MyClass::Mf() from DLL" << endl;}void f(){    cout"I‘m MiniMFC::f() from DLL" << endl;}

There are no exported functions in the resulting DLL file void f() . Use Dependency Walker to view the results as:

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Only the constructors and member functions of the class are exported, and the global function f() is not exported.

2 Cause Analysis

The definition of a function in the implementation file f() does not use namespaces MiniMFC , so only a function named in the global namespace is obtained, and the f function named in the namespace declared in the header file MiniMFC f does not implement the code. Let's change the function definition in the. cpp file to the following:

void f(){    cout"I‘m MiniMFC::f() from DLL" << endl;}

And then recompile, using Dependency Walker, you can see that this DLL does export a f function named, but it is global, not in the Minimfc namespace.

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3 Solutions

Knowing the reason, solving it is very simple, only need to use the f() Minimfc namespace to qualify in the definition of the implementation file. As shown below:

void MiniMFC::f(){    cout"I‘m MiniMFC::f() from DLL" << endl;}

After recompiling, this time the correct result was obtained:

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[email protected]@[email protected] @QAEXXZ
[email protected]@ @YAXXZ

VC + + Export functions with namespaces