Mono（linux）中的DLLImport崩溃：icall
我在Linux中遇到了Mono Interop的问题。 我有一个本地共享库（在Lazarus中制作），我需要在C＃程序集中使用它。 共享库由Windows和Linux上的Mono C＃组件使用。
该程序集在运行时通过DllImport加载共享库，并调用一个导出的函数来生成一个文件并返回一个包含新文件名的字符串。 共享库中的函数工作正常，但在Linux中，Mono运行时在函数返回时在Object .__ icall_wrapper_mono_marshal_free处崩溃。 这在Windows上使用Mono很好。
我做了几个测试，我可以知道共享库实际工作（新文件是在指定路径生成的），但最终运行时崩溃。 看起来，运行时将结果字符串封送回程序集时出现问题，因为如果我使用返回int的导出函数，则运行时会起作用。
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);
}
...
}
}
我尝试了几种方法（从导出的函数返回一个本地字符串，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）。
我确信我错过了一些东西，但我在Google上没有发现任何有关此问题的信息。
我的崩溃是：
=================================================================
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？
从本地方法调用返回string通常不是一个好主意。 请参考Mono的Interop with Native Libraries（字符串）页面，了解如何处理您的案例。 如果你知道返回字符串的最大尺寸，那么StringBuilder方法就是要走的路。
会发生什么情况是C＃试图释放分配给返回字符串的内存，这些内存使用Linux上的g_free或Windows上的CoTaskMemFree。 虽然您可以在程序中使用g_alloc或CoTaskMemAlloc来分配内存，但我建议将返回类型更改为C＃中的IntPtr，并使用Marshal.PtrToStringAuto将其转换为字符串。 您还需要通过将其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;
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，它被映射到libc free。 StrAlloc有可能做其他事情。
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