mono - Mono (linux) 中的 DLLImport 崩溃：ical_wrapper_mono_marshal_free

Question

我在 Linux 中遇到了 Mono Interop 的问题。我有一个需要在 C# 程序集中使用的本机共享库（用 Lazarus 制作）。Windows 和 Linux 上的 Mono C# 程序集使用共享库。

程序集在运行时通过 DllImport 加载共享库，并调用生成文件并返回带有新文件名的字符串的导出函数。共享库中的函数工作正常，但在 Linux 中，当函数返回时，Mono 运行时在 Object.__icall_wrapper_mono_marshal_free 处崩溃。在 Windows 上使用 Mono 可以正常工作。

我进行了几次测试，可以看出共享库确实有效（新文件在指定路径生成），但最终运行时崩溃。运行时似乎在将结果字符串封送回程序集方面存在问题，因为如果我使用返回 int 的导出函数，它就可以工作。

我的共享库是这样的：

library fileProcessing;

{$mode objfpc}{$H+}
...

function ProcessFile(File, ResultPath: PChar): PChar; cdecl; // returns a null-terminated string, with a C ABI calling convention
var
  sFile, sPath, sResult: string;
begin
  sFile := StrPas(File);
  sPath := StrPas(ResultPath);
...
  sResult := GenerateNewFile(sFile, sPath); // helper function that generates the file and returns its filename
  Result := stralloc(length(sResult) + 1);
  Result := strpcopy(Result, sResult);
end;
...

exports ProcessFile name 'ProcessFile';

调用 C# 程序集如下所示：

namespace SIG
{
  public class TsigKernel
  {
...
    [DllImport("fileProcessing.so", CharSet=CharSet.Ansi,
         EntryPoint="ProcessFile",
         CallingConvention=CallingConvention.Cdecl, SetLastError = true)]
    private static extern string ex_ProcessFile(string File, string ResultPath);

    // managed wrapper for the shared library exported function
    public string ProcessFile(string File, string ResultPath)
    {
     return ex_ProcessFile(File, ResultPath);
    }
...
  }
}

我尝试了几种替代方法（从导出的函数返回本机字符串，将调用约定更改为程序集和共享库上的 stdcall，更改 DllImport 中的字符集）。

我确定我遗漏了一些东西，但我在谷歌上没有找到任何关于这个问题的信息。

我的崩溃显示：

=================================================================  
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.  
=================================================================

Stacktrace:
  at (wrapper managed-to-native) object.__icall_wrapper_mono_marshal_free (intptr) <0x00004>
  at (wrapper managed-to-native) object.__icall_wrapper_mono_marshal_free (intptr) <0x00004>
  at (wrapper managed-to-native) SIG.TsigKernel.ex_ProcessFile (string, string) <0x00064>
  at SIG.TsigKernel.ProcessFile (string, string) <0x00010>
  at TEST.Form1.Form1_Load (object,System.EventArgs) <0x00047>
  at System.Windows.Forms.Form.OnLoad (System.EventArgs) <0x00060>
  at System.Windows.Forms.Form.OnLoadInternal (System.EventArgs) <0x00081>
  at System.Windows.Forms.Form.OnCreateControl () <0x00051>
  at System.Windows.Forms.Control.CreateControl () <0x0012e>
  at System.Windows.Forms.Control.WmShowWindow (System.Windows.Forms.Message&) <0x0010f>
  at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message&) <0x00292>
  at System.Windows.Forms.ScrollableControl.WndProc (System.Windows.Forms.Message&) <0x00013>
  at System.Windows.Forms.ContainerControl.WndProc (System.Windows.Forms.Message&) <0x00051>
  at System.Windows.Forms.Form.WndProc (System.Windows.Forms.Message&) <0x0022a>
  at System.Windows.Forms.Control/ControlWindowTarget.OnMessage (System.Windows.Forms.Message&) <0x0001d>
  at System.Windows.Forms.Control/ControlNativeWindow.WndProc (System.Windows.Forms.Message&) <0x0002d>
  at System.Windows.Forms.NativeWindow.WndProc (intptr,System.Windows.Forms.Msg,intptr,intptr) <0x001eb>
  at System.Windows.Forms.XplatUIX11.SendMessage (intptr,System.Windows.Forms.Msg,intptr,intptr) <0x002ae>
  at System.Windows.Forms.XplatUIX11.MapWindow (System.Windows.Forms.Hwnd,System.Windows.Forms.WindowType) <0x0019a>
  at System.Windows.Forms.XplatUIX11.CreateWindow (System.Windows.Forms.CreateParams) <0x00bb4>
  at System.Windows.Forms.XplatUI.CreateWindow (System.Windows.Forms.CreateParams) <0x0001d>
  at System.Windows.Forms.NativeWindow.CreateHandle (System.Windows.Forms.CreateParams) <0x00030>
  at System.Windows.Forms.Control.CreateHandle () <0x0007f>
  at System.Windows.Forms.Form.CreateHandle () <0x00014>
  at System.Windows.Forms.Control.CreateControl () <0x0008a>
  at System.Windows.Forms.Control.SetVisibleCore (bool) <0x00079>
  at System.Windows.Forms.Form.SetVisibleCore (bool) <0x0021d>
  at System.Windows.Forms.Control.set_Visible (bool) <0x0002c>
  at (wrapper remoting-invoke-with-check) System.Windows.Forms.Control.set_Visible (bool) <0x00057>
  at System.Windows.Forms.Application.RunLoop (bool,System.Windows.Forms.ApplicationContext) <0x001f9>
  at System.Windows.Forms.Application.Run (System.Windows.Forms.ApplicationContext) <0x00052>
  at System.Windows.Forms.Application.Run (System.Windows.Forms.Form) <0x00033>
  at TEST.Program.Main () <0x00044>
  at (wrapper runtime-invoke) object.runtime_invoke_void (object,intptr,intptr,intptr) <0x0003a>

Native stacktrace:
mono [0x80d36a9]
[0xffffe410]
[0xffffe430]
/lib/libc.so.6(gsignal+0x4f) [0xb76430cf]
/lib/libc.so.6(abort+0x187) [0xb76449e7]
/lib/libc.so.6 [0xb767f4ed]
/lib/libc.so.6 [0xb768550b]
/lib/libc.so.6 [0xb7686de4]
/lib/libc.so.6(cfree+0x6d) [0xb7689fdd]
/usr/lib/libglib-2.0.so.0(g_free+0x36) [0xb780d886]
[0xb6561634]
[0xb5786a5d]
[0xb57869d1]
[0xb57866c8]
[0xb5786599]
[0xb578632a]
[0xb5785f7a]
[0xb605dbe7]
[0xb578c7c0]
[0xb578bbfb]
[0xb57820c4]
[0xb578208a]
[0xb5781eeb]
[0xb578b95e]
[0xb578b936]
[0xb578ac74]
[0xb5788acf]
[0xb578c4b3]
[0xb605eca5]
[0xb605e0e6]
[0xb605e069]
[0xb605ddf0]
[0xb57804bd]
[0xb605db43]
[0xb57938a2]
[0xb57800a6]
[0xb57937f5]
[0xb5793798]
[0xb577f062]
[0xb577ee13]
[0xb577eacc]
[0xb71ce1f5]
[0xb71ce26b]
mono [0x8063552]

有任何想法吗？

score 2 · Accepted Answer

string从本地方法调用返回 a 通常不是一个好主意。请参阅 Mono 的与本机库（字符串）的互操作页面以了解如何处理您的情况。如果您知道返回字符串的最大大小，那么 StringBuilder 方法就是要走的路。

score 2 · Accepted Answer

发生的情况是 C# 尝试使用 Linux 上的 g_free 或 Windows 上的 CoTaskMemFree 释放为返回的字符串分配的内存。虽然您可以在程序中使用 g_alloc 或 CoTaskMemAlloc 来分配内存，但我建议在 C# 中将返回类型更改为 IntPtr 并使用 Marshal.PtrToStringAuto 将其转换为字符串。您还需要通过将返回的字符串传递给非托管代码中的某个其他函数来释放返回的字符串。

namespace SIG
{
  public class TsigKernel
  {
    ...
    [DllImport("fileProcessing.so", CharSet=CharSet.Ansi,
         EntryPoint="ProcessFile",
         CallingConvention=CallingConvention.Cdecl, SetLastError = true)]
    private static extern IntPtr ex_ProcessFile(string File, string ResultPath);

    [DllImport("fileProcessing.so", CharSet=CharSet.Ansi,
         EntryPoint="FreeText",
         CallingConvertion=CallingConvention.Cdecl, SetLastError = true)]
    private static extern void ex_FreeText(IntPtr str);

    // managed wrapper for the shared library exported function
    public string ProcessFile(string File, string ResultPath)
    {
      IntPtr str_ptr = ex_ProcessFile(File, ResultPath);
      string res = Marshal.PtrToStringAnsi(str_ptr);
      ex_FreeText(str_ptr);
      return res;
    }
    ...
  }
}

自由文本代码：

function FreeText(Str: PChar); cdecl; // frees previously allocated string, with a C ABI calling convention
begin
  strdispose(Str);
end;

score 0 · Accepted Answer

问题是 stralloc 使用什么？在 Mono 中，等效代码在返回的 blob 上使用 g_free，该 blob 映射到 libc free。StrAlloc 可能正在做其他事情。

mono - Mono (linux) 中的 DLLImport 崩溃：ical_wrapper_mono_marshal_free

3 回答 3

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