1. 兩個(gè)進(jìn)程訪問(wèn)同一個(gè)dll

2.寫入時(shí)復(fù)制（CopyOnWrite，簡(jiǎn)稱COW）思想

如果有多個(gè)調(diào)用者（Callers）同時(shí)訪問(wèn)相同的資源（如內(nèi)存或者是磁盤上的數(shù)據(jù)存儲(chǔ)），他們會(huì)共同獲取相同的指針指向相同的資源，直到某個(gè)調(diào)用者修改資源內(nèi)容時(shí)，系統(tǒng)才會(huì)真正復(fù)制一份專用副本（private copy）給該調(diào)用者， 只有更新操作，才會(huì)去復(fù)制一份新的數(shù)據(jù)并更新替換，否則都是訪問(wèn)同一個(gè)資源。

3. 注意點(diǎn)

3.1 不能傳指針作共享，每進(jìn)程有自己的內(nèi)存空間。

Each process gets its own address space. It is very important that pointers are never stored in a variable contained in a shared data segment. A pointer might be perfectly valid in one application but not in another.

3.2. 共享變量得初始化Any variables in a shared data segment must be statically initialized.

4.1 dll:

#pragma data_seg("MySec") int nDate = 0; #pragma data_seg() #pragma comment(linker,"/section:MySec,rws") _declspec(dllexport) void setIntData(int nDate1) {nDate = nDate1; }_declspec(dllexport) int getIntData() {return nDate; }

4.2 exe中的代碼：

void testSetFunc() {HINSTANCE hInst;hInst = LoadLibrary("Dll1.dll");typedef void (*setIntData)(int nDate1);setIntData setIntDataFunc = (setIntData)GetProcAddress(hInst, MAKEINTRESOURCE(5));if (!setIntDataFunc){return;}setIntDataFunc(66); }void testGetFunc() {HINSTANCE hInst;hInst = LoadLibrary("Dll1.dll");typedef int (*getIntData)();getIntData getIntDataFunc = (getIntData)GetProcAddress(hInst, MAKEINTRESOURCE(2));if (!getIntDataFunc){return;}int n = getIntDataFunc();char ch[256] = "\0";sprintf_s(ch, "%d", n);MessageBox(g_hWnd, ch, "f", MB_OK); }

4.3在兩個(gè)進(jìn)程exe中分別調(diào)用testSetFunc,testGetFunc將得到同一個(gè)結(jié)果。

【引用】
[1]: 代碼地址 https://github.com/thefistlei/os
[2]: How do I share data in my DLL with an application or with other DLLs https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2008/h90dkhs0(v=vs.90)?redirectedfrom=MSDN

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