从 dll 使用 CopyMemory 并抛出访问冲突错误

Question

我创建了一个用于 Unity5 C# 程序的 C++ .dll 库。

但是，当我运行来自 Unity 编辑器的程序并尝试调用 smCopy 时，Unity 崩溃并尝试发送错误报告；相反，我追踪到该错误是从 smCopy 发生的访问冲突错误。

.dll 库允许我连接到服务器并通过此函数将数据复制到给定参数中：

C++:
void DLL_API smCopy(const VOID *dest, SIZE_T len)
{
    CopyMemory((PVOID)(dest), (PVOID)(mapBuffer), len);
}

在我的 Unity 脚本中，我导入函数：

C#:
[DllImport(DLL_NAME, EntryPoint = "smCopy")] 
private static extern void smCopyData(IntPtr dest, IntPtr len);

并最终调用它：

C#:
{
 //  create IntPtr for message
    IntPtr msg_intptr = new IntPtr();

    smCopyData(msg_intptr, (IntPtr)Marshal.SizeOf(typeof(smMsg)));

    //  create actual data struct
        // smMsg is a struct referenced in both .dll & Unity script
    smMsg data_msg = new smMsg();

    //  Set POINTER data to struct
    Marshal.PtrToStructure(msg_intptr, data_msg);
}

我调试跟踪到smCopyData出现的错误，在日志中发现如下错误：

  `VCRUNTIME140D.dll caused an Access Violation (0xc0000005) in module VCRUNTIME140D.dll at 0033:b4761c89.`

.dll 与其他函数一起工作，我能够成功连接到服务器，除了出现这个错误。

现在我不知道下一步该怎么做，因为我需要这个函数将数据从服务器复制到结构中。

我如何才能将内存从服务器 (mapBuffer) 复制到 C# 的参数变量中？

Reference to Marshal & IntPtr

Editor.log 堆栈跟踪

0x00007FFBB70A1C89 (VCRUNTIME140D) memcpy
0x00007FFBB72819D9 (SharedMemoryClientDLL) [l:\projects\google\chapstick\software\working\abner\misc proj\vs\sharedmemoryclientdll\sharedmemoryclientdll\smclibrary.cpp:151] smCopy 
0x0000000012B65B29 (Mono JIT Code) (wrapper managed-to-native) SMCScript:smCopyData (intptr,intptr)
0x0000000012B65793 (Mono JIT Code) [L:\Projects\Google\chapstick\Software\Working\Abner\Misc Proj\Unity\ChapstickProject\Assets\Scripts\SMCScript.cs:202] SMCScript:GetData () 
0x0000000012B62CA3 (Mono JIT Code) [L:\Projects\Google\chapstick\Software\Working\Abner\Misc Proj\Unity\ChapstickProject\Assets\Scripts\SMCScript.cs:176] SMCScript:CheckForEvent () 
0x0000000010B69232 (Mono JIT Code) [L:\Projects\Google\chapstick\Software\Working\Abner\Misc Proj\Unity\ChapstickProject\Assets\Scripts\SMCScript.cs:150] SMCScript:Update () 
0x00000000007D68E2 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
0x00007FFB9B5F41BF (mono) [c:\buildslave\mono-runtime-and-classlibs\build\mono\mini\mini.c:4937] mono_jit_runtime_invoke 
0x00007FFB9B548435 (mono) [c:\buildslave\mono-runtime-and-classlibs\build\mono\metadata\object.c:2623] mono_runtime_invoke 
0x000000014033E20F (Unity) scripting_method_invoke

Answer 1

您需要分配一个缓冲区并将其指针传递给函数。您只是传递了一个空指针，因此 cpp 函数试图写入地址 0，这会导致访问冲突异常。

var len = Marshal.SizeOf(typeof(smMsg));
IntPtr msg_intptr = Marshal.AllocHGlobal(len);
try {
    // call the function, convert output to struct, etc...
}
finally {
    Marshal.FreeHGlobal(msg_intptr);
}

从 dll 使用 CopyMemory 并抛出访问冲突错误

Using CopyMemory from dll and throwing Access Violation Error

c#

c++

dll

access-violation

unity5