Posted on 2010-02-17 21:42
S.l.e!ep.￠% 阅读(647)
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VC
//
The following ifdef block is the standard way of creating macros which make exporting
//
from a DLL simpler. All files within this DLL are compiled with the TESTDLL_EXPORTS
//
symbol defined on the command line. this symbol should not be defined on any project
//
that uses this DLL. This way any other project whose source files include this file see
//
TESTDLL_API functions as being imported from a DLL, wheras this DLL sees symbols
//
defined with this macro as being exported.
#ifdef TESTDLL_EXPORTS
#define
TESTDLL_API __declspec(dllexport)
#else
#define
TESTDLL_API __declspec(dllimport)
#endif
#pragma data_seg (
"
.shared
"
)
int
g_TestValue
=
0
;
#pragma data_seg ()
#pragma comment(linker,
"
/SECTION:.shared,RWS
"
)
TESTDLL_API
int
getTestValue(
void
);
TESTDLL_API
void
setTestValue(
int
nValue);
//
testDLL.cpp : Defines the entry point for the DLL application.
//
#include
"
stdafx.h
"
#include
"
testDLL.h
"
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
switch
(ul_reason_for_call)
{
case
DLL_PROCESS_ATTACH:
case
DLL_THREAD_ATTACH:
case
DLL_THREAD_DETACH:
case
DLL_PROCESS_DETACH:
break
;
}
return
TRUE;
}
//
This is an example of an exported function.
TESTDLL_API
int
getTestValue(
void
)
{
return
g_TestValue;
}
TESTDLL_API
void
setTestValue(
int
nValue)
{
g_TestValue
=
nValue;
}
EXPORTS
getTestValue @
1
setTestValue @
2
接下来，实践证明一下
BOOL CTestCallDLLDlg::OnInitDialog()
{
CDialog::OnInitDialog();
// 
// TODO: Add extra initialization here
m_hModule = ::LoadLibrary("C:\\Documents and Settings\\Administrator\\桌面\\testDLL.dll");
return TRUE; // return TRUE unless you set the focus to a control
} void CTestCallDLLDlg::OnButton1()
{
typedef int (*getTestValueType)(void);
getTestValueType pfngetTestValue = (getTestValueType)::GetProcAddress(m_hModule, "getTestValue");
int i = pfngetTestValue();
CString str;
str.Format("The Value now is %d", i);
AfxMessageBox(str);
}
void CTestCallDLLDlg::OnButton2()
{
typedef int (*getTestValueType)(void);
getTestValueType pfngetTestValue = (getTestValueType)::GetProcAddress(m_hModule, "getTestValue");
typedef void (*setTestValueType)(int nValue);
setTestValueType pfnsetTestValue = (setTestValueType)::GetProcAddress(m_hModule, "setTestValue");
int i = pfngetTestValue() + 1;
pfnsetTestValue(i);
i = pfngetTestValue();
CString str;
str.Format("The Value now is %d", i);
AfxMessageBox(str);
}
奇迹般地，两个EXE拷到不同的地方，运行了两个实例，它们能够“数据共享”
加上下面两个功能:
void CTestCallDLLDlg::OnButton3()
{
::FreeLibrary(m_hModule);
m_hModule = NULL;
}
void CTestCallDLLDlg::OnButton4()
{
// TODO: Add your control notification handler code here
m_hModule = ::LoadLibrary("C:\\Documents and Settings\\Administrator\\桌面\\testDLL.dll");
}
就会发现，如果当所有EXE的实例都把 DLL 卸装再 Load 时，DLL的数据会清0.......
所以，为了“共享数据”，DLL必须至少有一个“引用（被某个EXE引用）”