Posted on 2010-02-17 21:42
S.l.e!ep.￠% 閱讀(654)
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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
接下來，實踐證明一下
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);????
}
奇跡般地，兩個EXE拷到不同的地方，運行了兩個實例，它們能夠“數據共享”
加上下面兩個功能:
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");
}
就會發現，如果當所有EXE的實例都把 DLL 卸裝再 Load 時，DLL的數據會清0.......
所以，為了“共享數據”，DLL必須至少有一個“引用（被某個EXE引用）”