c# - 调用 native 函数时最后一个参数出现损坏

Question

正在为 native (C) 库开发 C# 包装器。我在 native 库中有以下函数原型(prototype):

typedef struct _NativeObj *       NativeObj;
typedef struct AnotherNativeObj * AnotherNative;

__declspec(dllimport) NativeObj createNativeObj (
    AnotherNative * anotherNative,
    FirstCallback   firstCallback,
    void *          firstOpaque,
    SecondCallback  secondCallback,
    void *          secondOpaque,
    ThirdCallback   thirdCallback,
    void *          thirdOpaque,
    const char *    firstString,
    const char *    secondString,
    const char *    thirdString,
    time_t          timeout,
    char *          fourthString,
    int             firstInt,
    int             secondInt,
    int             thirdInt,
    int             fourthInt,
    char *          fifthString,
    int             fifthInt,
    char *          sixthString);

这是 C# 代码中的声明:

public delegate int ThirdCallbackDelegate(...);

public const uint NO_TIMEOUT = 0;

private uint   timeout   = NO_TIMEOUT;
private string fourthString;
private uint   firstInt  = 0;
private bool   secondInt = false;
private bool   thirdInt  = true;
private bool   fourthInt = true;
private string fifthString;
private bool   fifthInt  = false;
public string  sixthString { get; set; }

[DllImport("path\\to.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern IntPtr createNativeObj(
    IntPtr                 anotherNative,
    FirstCallbackDelegate  firstCallback,
    IntPtr                 firstOpaque,
    SecondCallbackDelegate secondCallback,
    IntPtr                 secondOpaque,
    ThirdCallbackDelegate  thirdCallback,
    IntPtr                 thirdOpaque,
    string                 firstString,
    string                 secondString,
    string                 thirdString,
    int                    timeout,
    string                 fourthString,
    int                    firstInt,
    int                    secondInt,
    int                    thirdInt,
    int                    fourthInt,
    string                 fifthString,
    int                    fifthInt,
    string                 sixthString);

参数背后的逻辑:

IntPtr myOpaque = createNativeObj(IntPtr.Zero,
            null,
            IntPtr.Zero,
            null,
            IntPtr.Zero,
            thirdCallbackDelegate,
            IntPtr.Zero,
            firstString,
            secondString,
            thirdString,
            (int)timeout,
            fourthString,
            (int)firstInt,
            Convert.ToInt32(secondInt),
            Convert.ToInt32(thirdInt),
            Convert.ToInt32(fourthInt),
            fifthString,
            Convert.ToInt32(fifthInt),
            sixthString);

在运行时，就在 native 函数开始时，超时后参数的值被损坏。

Answer 1

在 Windows 上，使用 MS 工具，并假设您未定义 _USE_32BIT_TIME_T，则 time_t 类型为 8 字节宽。这意味着您需要在 C# p/invoke 代码中将其声明为 long 才能匹配。