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  • Calling cdecl Functions That Have Different Number of Arguments

    - by KlaxSmashing
    I have functions that I wish to call based on some input. Each function has different number of arguments. In other words, if (strcmp(str, "funcA") == 0) funcA(a, b, c); else if (strcmp(str, "funcB") == 0) funcB(d); else if (strcmp(str, "funcC") == 0) funcC(f, g); This is a bit bulky and hard to maintain. Ideally, these are variadic functions (e.g., printf-style) and can use varargs. But they are not. So exploiting the cdecl calling convention, I am stuffing the stack via a struct full of parameters. I'm wondering if there's a better way to do it. Note that this is strictly for in-house (e.g., simple tools, unit tests, etc.) and will not be used for any production code that might be subjected to malicious attacks. Example: #include <stdio.h> typedef struct __params { unsigned char* a; unsigned char* b; unsigned char* c; } params; int funcA(int a, int b) { printf("a = %d, b = %d\n", a, b); return a; } int funcB(int a, int b, const char* c) { printf("a = %d, b = %d, c = %s\n", a, b, c); return b; } int funcC(int* a) { printf("a = %d\n", *a); *a *= 2; return 0; } typedef int (*f)(params); int main(int argc, char**argv) { int val; int tmp; params myParams; f myFuncA = (f)funcA; f myFuncB = (f)funcB; f myFuncC = (f)funcC; myParams.a = (unsigned char*)100; myParams.b = (unsigned char*)200; val = myFuncA(myParams); printf("val = %d\n", val); myParams.c = (unsigned char*)"This is a test"; val = myFuncB(myParams); printf("val = %d\n", val); tmp = 300; myParams.a = (unsigned char*)&tmp; val = myFuncC(myParams); printf("a = %d, val = %d\n", tmp, val); return 0; } Output: gcc -o func func.c ./func a = 100, b = 200 val = 100 a = 100, b = 200, c = This is a test val = 200 a = 300 a = 600, val = 0

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  • How do I compile boost using __cdecl calling convention?

    - by Sorin Sbarnea
    I have a project compiled using __cdecl calling convention (msvc2010) and I compiled boost using the same compiler using the default settings. The project linked with boost but I at runtime I got an assert message like this: File: ...\boost\boost\program_options\detail\parsers.hpp Line: 79 Run-Time Check Failure #0 - The value of ESP was not properly saved across a function call. This is usually a result of calling a function declared with one calling convention with a function pointer declared with a different calling convention. There are the following questions: what calling convention does boost build with by default on Windows (msvc2010) how to I compile boost with __cdecl calling convention why boost wasn't able to prevent linking with code with different calling conventions? I understood that boost has really smart library auto-inclusion code.

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  • Error While Linking Multiple C Object files in Delphi 2007

    - by Ramnish
    Hello Everyone. I am new to delphi. I was trying to add C Object files in my Delphi project and link them directly since Delphi Supports C Object Linking. I got it working when i link a single Object file. But when i try to link multiple object files, i am getting error 'Unsatisfied forward or external declaration'. I have tried this in Delphi 2007 as well as XE.So what am i doing wrong here? Working Code: function a_function():Integer;cdecl; implementation {$Link 'a.obj'} function a_function():Integer;cdecl;external; end. Error Code: function a_function():Integer;cdecl; function b_function();Integer;cdecl; function c_function();Integer;cdecl; implementation {$LINK 'a.obj'} {$LINK 'b.obj'} {$LINK 'c.obj'} function a_function():Integer;cdecl;external; function b_function();Integer;cdecl;external; function c_function();Integer;cdecl;external; end.

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  • System.EntryPointNotFoundException:while importing libsrp in a c# code under ubuntu

    - by Hema Joshi
    hi, i am importing libsrp.so in a c# code under ubuntu.my code is using System; using System.IO; using System.Text; using System.Runtime.InteropServices; namespace Main { public static class Test { [DllImport("libsrp.so" ,EntryPoint = "SRP_initialize_library", CallingConvention=CallingConvention.Cdecl)] public static extern int SRP_initialize_library(); [DllImport("libsrp.so" ,EntryPoint = "SRP_finalize_library", CallingConvention=CallingConvention.Cdecl)] public static extern int SRP_finalize_library(); } public class Test1 { public static void Main( string[] args ) { Console.Write("output is:", Test.SRP_initialize_library()); Test. SRP_finalize_library(); Console.Write("\n"); } } } but while runnign the code using mono i am finding error Unhandled Exception: System.EntryPointNotFoundException: SRP_initialize_library at (wrapper managed-to-native) Main.Test:SRP_initialize_library () at Main.Test1.Main (System.String[] args) [0x00000] i am unable to find what is the problem? please tell me where is the problem?

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  • Employing elegance in order to evade importing elephants: a case of excessive dll Imports

    - by user994179
    I am writing C# code that interfaces to a legacy (Feb 2012) C program, using DllImport. It works fine, but I need to call more than 30 different functions, turning my normally impeccable, exquisite code into something of near-elephantine proportions. Surely there must be a way around this? [Warning: those with weak stomachs may want to avert their eyes from what follows]: [DllImport("C:\\Users\\mitt\\Documents\\Visual Studio 2010\\Projects\\mrSolution\\mr\\x64\\Debug\\mrDll.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)] public static extern bool mrEngine_initialize( [In, Out, MarshalAs(UnmanagedType.LPStruct)] PLOT_SPEC PlotSpec); [DllImport("C:\\Users\\mitt\\Documents\\Visual Studio 2010\\Projects\\mrSolution\\mr\\x64\\Debug\\mrDll.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)] public static extern bool mrEngine_getDataPoint( [In, Out, MarshalAs(UnmanagedType.LPStruct)] PLOT_SPEC PlotSpec);

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  • Using pinvoke in c# to call sprintf and friends on 64-bit

    - by bde
    I am having an interesting problem with using pinvoke in C# to call _snwprintf. It works for integer types, but not for floating point numbers. This is on 64-bit Windows, it works fine on 32-bit. My code is below, please keep in mind that this is a contrived example to show the behavior I am seeing. class Program { [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)] private static extern int _snwprintf([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, uint length, String format, int p); [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)] private static extern int _snwprintf([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, uint length, String format, double p); static void Main(string[] args) { Double d = 1.0f; Int32 i = 1; Object o = (object)d; StringBuilder str = new StringBuilder(); _snwprintf(str, 32, "%10.1f", (Double)o); Console.WriteLine(str.ToString()); o = (object)i; _snwprintf(str, 32, "%10d", (Int32)o); Console.WriteLine(str.ToString()); Console.ReadKey(); } } The output of this program is 0.0 1 It should print 1.0 on the first line and not 0.0, and so far I am stumped.

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  • ASP.NET 2.0 app runs on Win 2003 in IIS 5 isolation mode but not in (default) IIS 6 mode

    - by Tex
    The app uses DLLImport to call a legacy unmanaged dll. Let's call this dll Unmanaged.dll for the sake of this question. Unmanaged.dll has dependencies on 5 other legacy dll's. All of the legacy dll's are placed in the WebApp/bin/ directory of my ASP.NET application. When IIS is running in 5.0 isolation mode, the app works fine - calls to the legacy dll are processed without error. When IIS is running in the default 6.0 mode, the app is able to initiate the Unmanaged.dll (InitMe()), but dies during a later call to it (ProcessString()). I'm pulling my hair out here. I've moved the unmanaged dll's to various locations, tried all kinds of security settings and searched long and hard for a solution. Help! Sample code: [DllImport("Unmanaged.dll", EntryPoint="initME", CharSet=System.Runtime.InteropServices.CharSet.Ansi, CallingConvention=CallingConvention.Cdecl)] internal static extern int InitME(); //Calls to InitMe work fine - Unmanaged.dll initiates and writes some entries in a dedicated log file [DllImport("Unmanaged.dll", EntryPoint="processString", CharSet=System.Runtime.InteropServices.CharSet.Ansi, CallingConvention=CallingConvention.Cdecl)] internal static extern int ProcessString(string inStream, int inLen, StringBuilder outStream, ref int outLen, int maxLen); //Calls to ProcessString cause the app to crash, without leaving much of a trace that I can find so far

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  • C# DllImport with c++ const char* not working correctly

    - by Shammah
    I have the following function in a C++ DLL extern "C" __declspec(dllexport) bool Exist(const char* name) { //if (g_Queues.find(name) != g_Queues.end()) // return true; //else // return false; return false; } Inside my C# class I have the following: [DllImport("Whisper.dll", EntryPoint="Exist", CallingConvention=CallingConvention.Cdecl)] public static extern bool Exist(string name); Yet, whenever I call my function it ALWAYS returns true, even when I commented out my little function and made it return false. I have the feeling there is something wrong with my calling convention or any other issue with P/Invoking my DLL, probably corresponding with the string and const char*, but for now I am completely clueless. What am I doing wrong? Why does it return true instead of false? EDIT: I have figured out this has nothing to do with the const char* or string, because the problem persists with an empty function. I've tried changing the calling convention between Cdecl and StdCall and neither work correctly. I've also managed to debug my DLL and it's being called correctly and does indeed return false, but once back into C# it somehow is true. Changing the CharSet also had no effect. I've made sure I've supplied my C# program with the latest and correct version of my DLL each time, so that shouldn't be an issue aswell. Again, I am completely clueless on why the result is true when I'm in fact returning false. EDIT2: SOReader provided me with a suggestion which fixes another important issue, see my comment. Sadly, it does not fix the return issue.

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  • C++ int vector to c#

    - by Stefan Koenen
    I'm doing a C# project and I want to call next_permutation from the algorithm library in C++. I found the way to call c++ functions in c# but i dont know how to get vectors from c++ and use it in c# (cause next_permutation require a int vector...) this is what I'm trying at the moment: extern void NextPermutation(vector<int>& permutation) { next_permutation (permutation.begin(),permutation.end()); } [DllImport("PEDLL.dll", CallingConvention = CallingConvention.Cdecl)] private static extern void NextPermutation(IntPtr test);

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  • Assembly stack persistency

    - by user246100
    Hello. I would like to know if after calling functions the data I have in the stack is persistent. Like, I would like to know if (assuming cdecl convention) can I do this (independently of function X and independently of optimizations): push 1 push 2 push 3 call X call X call X add 12 esp ? Also, let's say that before the calls I save the address of where the pushed values are in a global variable. Can I, inside X, alter the values it contain by acessing the global variable? Like, for some reason I want that in X I'm able to alter the values in stack so that the second and third call to X receive different values.

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  • How to link Delphi with C++?

    - by CyberShadow
    cpp.cpp extern "C" char* GetText() { return "Hello, world!"; } delphi.dpr {$APPTYPE CONSOLE} {$LINK 'cpp.obj'} function _GetText: PChar; cdecl; external; begin WriteLn(_GetText); end. I can't get this to work, no matter what I try. I tried various calling conventions, playing with underscores. even creating a .c wrapper for the .cpp code (but then the .c wrapper doesn't "see" any .cpp symbols). I'm about to give up and use DLLs. Any suggestions?

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  • How to call in C# function from Win32 DLL with custom objects

    - by marko
    How to use in C# function from Win32 DLL file made in Delphi. When function parameters are custom delphi objects? Function definition in Delphi: function GetAttrbControls( Code : PChar; InputList: TItemList; var Values : TValArray): Boolean; stdcall; export; Types that use: type TItem = packed record Code : PChar; ItemValue: Variant; end; TItemList = array of TItem; TValArray = array of PChar; Example in C# (doesn't work): [StructLayout(LayoutKind.Sequential)] public class Input { public string Code; public object ItemValue; }; [DllImport("Filename.dll", EntryPoint = "GetValues", CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)] public static extern bool GetValues(string Code, Input[] InputList, ref StringBuilder[] Values);

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  • Having problem dynamically invoking unmanaged VB COM dll from c#?

    - by Ramesh Vel
    I have a problem calling unmanaged VB COM dll from c#. This is dynamic invocation using loadLibrary and GetProcAddress. I can successfully loaded the dll using loadLibrary , but the GetProcAddress always return 0. It wasnt log any error msg and nothing. it just returns 0. below the sample code VB COM VERSION 1.0 CLASS BEGIN MultiUse = -1 Persistable = 0 DataBindingBehavior = 0 DataSourceBehavior = 0 MTSTransactionMode = 0 END Attribute VB_Name = "Sample" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = True Attribute VB_PredeclaredId = False Attribute VB_Exposed = True Option Explicit Private Attribute1 As String Private Sub Class_Initialize() Attribute1 = "test" End Sub Public Sub TestSub() End Sub Public Function testFunction() As String testFunction = "default.html" End Function Public Function SetData(XML As String) As String SetData = Date + Time End Function c# code static class UnManagedInvoker { [DllImport("kernel32.dll")] private static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string dllToLoad); [DllImport("kernel32.dll")] private static extern IntPtr GetProcAddress(IntPtr hModule, [MarshalAs(UnmanagedType.LPStr)] string procedureName); [DllImport("kernel32.dll")] private static extern bool FreeLibrary(IntPtr hModule); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] public delegate string MethodToInvoke(string sdata); public static string InvokeUnmanagedDll(string dllPath, string methodName) { IntPtr DIedDll = LoadLibrary(dllPath); IntPtr AddressOfFunction = GetProcAddress(DIedDll, methodName); MethodToInvoke MI = (MethodToInvoke)Marshal.GetDelegateForFunctionPointer(AddressOfFunction, typeof(MethodToInvoke)); string data = MI("ssdasda"); FreeLibrary(DIedDll); return data; } } And the calling code string res = UnManagedInvoker.InvokeUnmanagedDll("xx.dll","SetData"); Can someone help me out.. Update: I can successfully call the methods if the component is registered. using the below code Type Med = Type.GetTypeFromCLSID(new Guid("089DD8B0-E12B-439B-B52C-007CA72C93D0")); object MedObj = Activator.CreateInstance(Med); object[] parameter = new object[1]; parameter[0] = "asdasd"; var ss = Med.InvokeMember("SetData", System.Reflection.BindingFlags.InvokeMethod, null, MedObj, parameter); is there a way if the dll not registered.?

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  • How to tell endianness from this output?

    - by Nick Rosencrantz
    I'm running this example program and I'm suppossed to be able to tell from the output what machine type it is. I'm certain it's from inspecting one or two values but how should I perform this inspection? /* pointers.c - Test pointers * Written 2012 by F Lundevall * Copyright abandoned. This file is in the public domain. * * To make this program work on as many systems as possible, * addresses are converted to unsigned long when printed. * The 'l' in formatting-codes %ld and %lx means a long operand. */ #include <stdio.h> #include <stdlib.h> int * ip; /* Declare a pointer to int, a.k.a. int pointer. */ char * cp; /* Pointer to char, a.k.a. char pointer. */ /* Declare fp as a pointer to function, where that function * has one parameter of type int and returns an int. * Use cdecl to get the syntax right, http://cdecl.org/ */ int ( *fp )( int ); int val1 = 111111; int val2 = 222222; int ia[ 17 ]; /* Declare an array of 17 ints, numbered 0 through 16. */ char ca[ 17 ]; /* Declare an array of 17 chars. */ int fun( int parm ) { printf( "Function fun called with parameter %d\n", parm ); return( parm + 1 ); } /* Main function. */ int main() { printf( "Message PT.01 from pointers.c: Hello, pointy World!\n" ); /* Do some assignments. */ ip = &val1; cp = &val2; /* The compiler should warn you about this. */ fp = fun; ia[ 0 ] = 11; /* First element. */ ia[ 1 ] = 17; ia[ 2 ] = 3; ia[ 16 ] = 58; /* Last element. */ ca[ 0 ] = 11; /* First element. */ ca[ 1 ] = 17; ca[ 2 ] = 3; ca[ 16 ] = 58; /* Last element. */ printf( "PT.02: val1: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val1, val1, val1 ); printf( "PT.03: val2: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val2, val2, val2 ); printf( "PT.04: ip: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &ip, (long) ip, (long) ip ); printf( "PT.05: Dereference pointer ip and we find: %d \n", *ip ); printf( "PT.06: cp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &cp, (long) cp, (long) cp ); printf( "PT.07: Dereference pointer cp and we find: %d \n", *cp ); *ip = 1234; printf( "\nPT.08: Executed *ip = 1234; \n" ); printf( "PT.09: val1: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val1, val1, val1 ); printf( "PT.10: ip: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &ip, (long) ip, (long) ip ); printf( "PT.11: Dereference pointer ip and we find: %d \n", *ip ); printf( "PT.12: val1: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val1, val1, val1 ); *cp = 1234; /* The compiler should warn you about this. */ printf( "\nPT.13: Executed *cp = 1234; \n" ); printf( "PT.14: val2: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val2, val2, val2 ); printf( "PT.15: cp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &cp, (long) cp, (long) cp ); printf( "PT.16: Dereference pointer cp and we find: %d \n", *cp ); printf( "PT.17: val2: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val2, val2, val2 ); ip = ia; printf( "\nPT.18: Executed ip = ia; \n" ); printf( "PT.19: ia[0]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ia[0], ia[0], ia[0] ); printf( "PT.20: ia[1]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ia[1], ia[1], ia[1] ); printf( "PT.21: ip: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &ip, (long) ip, (long) ip ); printf( "PT.22: Dereference pointer ip and we find: %d \n", *ip ); ip = ip + 1; /* add 1 to pointer */ printf( "\nPT.23: Executed ip = ip + 1; \n" ); printf( "PT.24: ip: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &ip, (long) ip, (long) ip ); printf( "PT.25: Dereference pointer ip and we find: %d \n", *ip ); cp = ca; printf( "\nPT.26: Executed cp = ca; \n" ); printf( "PT.27: ca[0]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ca[0], ca[0], ca[0] ); printf( "PT.28: ca[1]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ca[1], ca[1], ca[1] ); printf( "PT.29: cp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &cp, (long) cp, (long) cp ); printf( "PT.30: Dereference pointer cp and we find: %d \n", *cp ); cp = cp + 1; /* add 1 to pointer */ printf( "\nPT.31: Executed cp = cp + 1; \n" ); printf( "PT.32: cp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &cp, (long) cp, (long) cp ); printf( "PT.33: Dereference pointer cp and we find: %d \n", *cp ); ip = ca; /* The compiler should warn you about this. */ printf( "\nPT.34: Executed ip = ca; \n" ); printf( "PT.35: ca[0]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ca[0], ca[0], ca[0] ); printf( "PT.36: ca[1]: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &ca[1], ca[1], ca[1] ); printf( "PT.37: ip: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &ip, (long) ip, (long) ip ); printf( "PT.38: Dereference pointer ip and we find: %d \n", *ip ); cp = ia; /* The compiler should warn you about this. */ printf( "\nPT.39: Executed cp = ia; \n" ); printf( "PT.40: cp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &cp, (long) cp, (long) cp ); printf( "PT.41: Dereference pointer cp and we find: %d \n", *cp ); printf( "\nPT.42: fp: stored at %lx (hex); value is %ld (dec), %lx (hex)\n", (long) &fp, (long) fp, (long) fp ); printf( "PT.43: Dereference fp and see what happens.\n" ); val1 = (*fp)(42); printf( "PT.44: Executed val1 = (*fp)(42); \n" ); printf( "PT.45: val1: stored at %lx (hex); value is %d (dec), %x (hex)\n", (long) &val1, val1, val1 ); return( 0 ); } Output Message PT.01 from pointers.c: Hello, pointy World! PT.02: val1: stored at 21e50 (hex); value is 111111 (dec), 1b207 (hex) PT.03: val2: stored at 21e54 (hex); value is 222222 (dec), 3640e (hex) PT.04: ip: stored at 21eb8 (hex); value is 138832 (dec), 21e50 (hex) PT.05: Dereference pointer ip and we find: 111111 PT.06: cp: stored at 21e6c (hex); value is 138836 (dec), 21e54 (hex) PT.07: Dereference pointer cp and we find: 0 PT.08: Executed *ip = 1234; PT.09: val1: stored at 21e50 (hex); value is 1234 (dec), 4d2 (hex) PT.10: ip: stored at 21eb8 (hex); value is 138832 (dec), 21e50 (hex) PT.11: Dereference pointer ip and we find: 1234 PT.12: val1: stored at 21e50 (hex); value is 1234 (dec), 4d2 (hex) PT.13: Executed *cp = 1234; PT.14: val2: stored at 21e54 (hex); value is -771529714 (dec), d203640e (hex) PT.15: cp: stored at 21e6c (hex); value is 138836 (dec), 21e54 (hex) PT.16: Dereference pointer cp and we find: -46 PT.17: val2: stored at 21e54 (hex); value is -771529714 (dec), d203640e (hex) PT.18: Executed ip = ia; PT.19: ia[0]: stored at 21e74 (hex); value is 11 (dec), b (hex) PT.20: ia[1]: stored at 21e78 (hex); value is 17 (dec), 11 (hex) PT.21: ip: stored at 21eb8 (hex); value is 138868 (dec), 21e74 (hex) PT.22: Dereference pointer ip and we find: 11 PT.23: Executed ip = ip + 1; PT.24: ip: stored at 21eb8 (hex); value is 138872 (dec), 21e78 (hex) PT.25: Dereference pointer ip and we find: 17 PT.26: Executed cp = ca; PT.27: ca[0]: stored at 21e58 (hex); value is 11 (dec), b (hex) PT.28: ca[1]: stored at 21e59 (hex); value is 17 (dec), 11 (hex) PT.29: cp: stored at 21e6c (hex); value is 138840 (dec), 21e58 (hex) PT.30: Dereference pointer cp and we find: 11 PT.31: Executed cp = cp + 1; PT.32: cp: stored at 21e6c (hex); value is 138841 (dec), 21e59 (hex) PT.33: Dereference pointer cp and we find: 17 PT.34: Executed ip = ca; PT.35: ca[0]: stored at 21e58 (hex); value is 11 (dec), b (hex) PT.36: ca[1]: stored at 21e59 (hex); value is 17 (dec), 11 (hex) PT.37: ip: stored at 21eb8 (hex); value is 138840 (dec), 21e58 (hex) PT.38: Dereference pointer ip and we find: 185664256 PT.39: Executed cp = ia; PT.40: cp: stored at 21e6c (hex); value is 138868 (dec), 21e74 (hex) PT.41: Dereference pointer cp and we find: 0 PT.42: fp: stored at 21e70 (hex); value is 69288 (dec), 10ea8 (hex) PT.43: Dereference fp and see what happens. Function fun called with parameter 42 PT.44: Executed val1 = (*fp)(42); PT.45: val1: stored at 21e50 (hex); value is 43 (dec), 2b (hex)

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  • How do I import and call unmanaged C dll with ansi string "char *" pointer string from VB.net?

    - by Warren P
    I have written my own function, which in C would be declared like this, using standard Win32 calling conventions: int Thing( char * command, char * buffer, int * BufSize); I have the following amount of VB figured out, which should import the dll and call this function, wrapping it up to make it easy to call Thing("CommandHere",GetDataBackHere): Imports Microsoft.VisualBasic Imports System.Runtime.InteropServices Imports System Imports System.Text Namespace dllInvocationSpace Public Class dllInvoker ' tried attributes but could not make it build: ' <DllImport("Thing1.dll", False, CallingConvention.Cdecl, CharSet.Ansi, "Baton", True, True, False, True)> Declare Ansi Function Thing Lib "Thing1.dll" (ByVal Command As String, ByRef Buffer As String, ByRef BufferLength As Integer) Shared Function dllCall(ByVal Command As String, ByRef Results As String) As Integer Dim Buffer As StringBuilder = New StringBuilder(65536) Dim retCode As Integer Dim bufsz As Integer bufsz = 65536 retCode = Thing(Command, Buffer, bufsz) Results = Buffer Return retCode End Function End Class End Namespace The current code doesn't build, because although I think I should be able to create a "buffer" that the C Dll can write data back into using a string builder, I haven't got it quite right. (Value of type System.Text.STringBuilder cannot be converted to 'String'). I have looked all over the newsgroups and forums and can not find an example where the C dll needs to pass between 1 and 64kbytes of data back (char *buffer, int bufferlen) to visual basic.net.

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  • Cannot call DLL import entry in C# from C++ project. EntryPointNotFoundException

    - by kriau
    I'm trying to call from C# a function in a custom DLL written in C++. However I'm getting the warning during code analysis and the error at runtime: Warning: CA1400 : Microsoft.Interoperability : Correct the declaration of 'SafeNativeMethods.SetHook()' so that it correctly points to an existing entry point in 'wi.dll'. The unmanaged entry point name currently linked to is SetHook. Error: System.EntryPointNotFoundException was unhandled. Unable to find an entry point named 'SetHook' in DLL 'wi.dll'. Both projects wi.dll and C# exe has been compiled in to the same DEBUG folder, both files reside here. There is only one file with the name wi.dll in the whole file system. C++ function definition looks like: #define WI_API __declspec(dllexport) bool WI_API SetHook(); I can see exported function using Dependency Walker: as decorated: bool SetHook(void) as undecorated: ?SetHook@@YA_NXZ C# DLL import looks like (I've defined these lines using CLRInsideOut from MSDN magazine): [DllImport("wi.dll", EntryPoint = "SetHook", CallingConvention = CallingConvention.Cdecl)] [return: MarshalAsAttribute(UnmanagedType.I1)] internal static extern bool SetHook(); I've tried without EntryPoint and CallingConvention definitions as well. Both projects are 32-bits, I'm using W7 64 bits, VS 2010 RC. I believe that I simply have overlooked something.... Thanks in advance.

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  • Reference a GNU C DLL built in GCC against Cygwin, from C#/NET

    - by Dale Halliwell
    Here is what I want: I have a huge legacy C/C++ codebase written for POSIX, including some very POSIX specific stuff like pthreads. This can be compiled on Cygwin/GCC and run as an executable under Windows with the Cygwin DLL. What I would like to do is build the codebase itself into a Windows DLL that I can then reference from C# and write a wrapper around it to access some parts of it programatically. I have tried this approach with the very simple "hello world" example at http://www.cygwin.com/cygwin-ug-net/dll.html and it doesn't seem to work. #include <stdio.h> extern "C" __declspec(dllexport) int hello(); int hello() { printf ("Hello World!\n"); return 42; } I believe I should be able to reference a DLL built with the above code in C# using something like: [DllImport("kernel32.dll")] public static extern IntPtr LoadLibrary(string dllToLoad); [DllImport("kernel32.dll")] public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName); [DllImport("kernel32.dll")] public static extern bool FreeLibrary(IntPtr hModule); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate int hello(); static void Main(string[] args) { var path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "helloworld.dll"); IntPtr pDll = LoadLibrary(path); IntPtr pAddressOfFunctionToCall = GetProcAddress(pDll, "hello"); hello hello = (hello)Marshal.GetDelegateForFunctionPointer( pAddressOfFunctionToCall, typeof(hello)); int theResult = hello(); Console.WriteLine(theResult.ToString()); bool result = FreeLibrary(pDll); Console.ReadKey(); } But this approach doesn't seem to work. LoadLibrary returns null. It can find the DLL (helloworld.dll), it is just like it can't load it or find the exported function. I am sure that if I get this basic case working I can reference the rest of my codebase in this way. Any suggestions or pointers, or does anyone know if what I want is even possible? Thanks.

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  • Calling from C# to C function which accept a struct array allocated by caller

    - by lifey
    I have the following C struct struct XYZ { void *a; char fn[MAX_FN]; unsigned long l; unsigned long o; }; And I want to call the following function from C#: extern "C" int func(int handle, int *numEntries, XYZ *xyzTbl); Where xyzTbl is an array of XYZ of size numEntires which is allocated by the caller I have defined the following C# struct: [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential, CharSet = System.Runtime.InteropServices.CharSet.Ansi)] public struct XYZ { public System.IntPtr rva; [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = 128)] public string fn; public uint l; public uint o; } and a method: [System.Runtime.InteropServices.DllImport(@"xyzdll.dll", CallingConvention = CallingConvention.Cdecl)] public static extern Int32 func(Int32 handle, ref Int32 numntries, [MarshalAs(UnmanagedType.LPArray)] XYZ[] arr); Then I try to call the function : XYZ xyz = new XYZ[numEntries]; for (...) xyz[i] = new XYZ(); func(handle,numEntries,xyz); Of course it does not work. Can someone shed light on what I am doing wrong ?

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  • How to correctly pass a float from C# to C++ (dll)

    - by RavelT
    I'm getting huge differences when I pass a float from C# to C++. I'm passing a dynamic float wich changes over time. With a debuger I get this: c++ lonVel -0.036019072 float c# lonVel -0.029392920 float I did set my MSVC++2010 floating point model to /fp:fast wich should be the standard in .NET if I'm not mistaken, but this didnt help. Now I cant give out the code but I can show a fraction of it. From C# side it looks like this: namespace Example { public class Wheel { public bool loging = true; #region Members public IntPtr nativeWheelObject; #endregion Members public Wheel() { this.nativeWheelObject = Sim.Dll_Wheel_Add(); return; } #region Wrapper methods public void SetVelocity(float lonRoadVelocity,float latRoadVelocity){Sim.Dll_Wheel_SetVelocity(this.nativeWheelObject,lonRoadVelocity,latRoadVelocity);} #endregion Wrapper methods } internal class Sim { #region PInvokes [DllImport(pluginName, CallingConvention=CallingConvention.Cdecl)] public static extern void Dll_Wheel_SetVelocity(IntPtr wheel,float lonRoadVelocity,float latRoadVelocity); #endregion PInvokes } } And in C++ side @ exportFunctions.cpp: EXPORT_API void Dll_Wheel_SetVelocity(CarWheel* wheel,float lonRoadVelocity,float latRoadVelocity){ wheel->SetVelocity(lonRoadVelocity,latRoadVelocity);} So any sugestions on what I should do in order to get 1:1 results or atleast 99% correct results.

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  • How to use Crtl in a Delphi unit in a C++Builder project? (or link to C++Builder C runtime library)

    - by Craig Peterson
    I have a Delphi unit that is statically linking a C .obj file using the {$L xxx} directive. The C file is compiled with C++Builder's command line compiler. To satisfy the C file's runtime library dependencies (_assert, memmove, etc), I'm including the crtl unit Allen Bauer mentioned here. unit FooWrapper; interface implementation uses Crtl; // Part of the Delphi RTL {$L FooLib.obj} // Compiled with "bcc32 -q -c foolib.c" procedure Foo; cdecl; external; end. If I compile that unit in a Delphi project (.dproj) everthing works correctly. If I compile that unit in a C++Builder project (.cbproj) it fails with the error: [ILINK32 Error] Fatal: Unable to open file 'CRTL.OBJ' And indeed, there isn't a crtl.obj file in the RAD Studio install folder. There is a .dcu, but no .pas. Trying to add crtdbg to the uses clause (the C header where _assert is defined) gives an error that it can't find crtdbg.dcu. If I remove the uses clause, it instead fails with errors that __assert and _memmove aren't found. So, in a Delphi unit in a C++Builder project, how can I export functions from the C runtime library so they're available for linking? I'm already aware of Rudy Velthuis's article. I'd like to avoid manually writing Delphi wrappers if possible, since I don't need them in Delphi, and C++Builder must already include the necessary functions. Edit For anyone who wants to play along at home, the code is available in Abbrevia's Subversion repository at https://tpabbrevia.svn.sourceforge.net/svnroot/tpabbrevia/trunk. I've taken David Heffernan's advice and added a "AbCrtl.pas" unit that mimics crtl.dcu when compiled in C++Builder. That got the PPMd support working, but the Lzma and WavPack libraries both fail with link errors: [ILINK32 Error] Error: Unresolved external '_beginthreadex' referenced from ABLZMA.OBJ [ILINK32 Error] Error: Unresolved external 'sprintf' referenced from ABWAVPACK.OBJ [ILINK32 Error] Error: Unresolved external 'strncmp' referenced from ABWAVPACK.OBJ [ILINK32 Error] Error: Unresolved external '_ftol' referenced from ABWAVPACK.OBJ AFAICT, all of them are declared correctly, and the _beginthreadex one is actually declared in AbLzma.pas, so it's used by the pure Delphi compile as well. To see it yourself, just download the trunk (or just the "source" and "packages" directories), disable the {$IFDEF BCB} block at the bottom of AbDefine.inc, and try to compile the C++Builder "Abbrevia.cbproj" project.

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  • CUDA not working in 64 bit windows 7

    - by Programmer
    I have cuda toolkit 4.0 installed in a 64 bit windows 7. I try building my cuda code, #include<iostream> #include"cuda_runtime.h" #include"cuda.h" __global__ void kernel(){ } int main(){ kernel<<<1,1>>>(); int c = 0; cudaGetDeviceCount(&c); cudaDeviceProp prop; cudaGetDeviceProperties(&prop, 0); std::cout<<"the name is"<<prop.name; std::cout<<"Hello World!"<<c<<std::endl; system("pause"); return 0; } but operation fails. Below is the build log: Build Log Rebuild started: Project: god, Configuration: Debug|Win32 Command Lines Creating temporary file "c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\Debug\BAT0000482007500.bat" with contents [ @echo off echo "C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\bin\nvcc.exe" -gencode=arch=compute_10,code=\"sm_10,compute_10\" -gencode=arch=compute_20,code=\"sm_20,compute_20\" --machine 32 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\include" -maxrregcount=0 --compile -o "Debug/sample.cu.obj" sample.cu "C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\bin\nvcc.exe" -gencode=arch=compute_10,code=\"sm_10,compute_10\" -gencode=arch=compute_20,code=\"sm_20,compute_20\" --machine 32 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\include" -maxrregcount=0 --compile -o "Debug/sample.cu.obj" "c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\sample.cu" if errorlevel 1 goto VCReportError goto VCEnd :VCReportError echo Project : error PRJ0019: A tool returned an error code from "Compiling with CUDA Build Rule..." exit 1 :VCEnd ] Creating command line """c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\Debug\BAT0000482007500.bat""" Creating temporary file "c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\Debug\RSP0000492007500.rsp" with contents [ /OUT:"C:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\Debug\god.exe" /LIBPATH:"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\lib\x64" /MANIFEST /MANIFESTFILE:"Debug\god.exe.intermediate.manifest" /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /DEBUG /PDB:"C:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\Debug\god.pdb" /DYNAMICBASE /NXCOMPAT /MACHINE:X86 cudart.lib cuda.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib ".\Debug\sample.cu.obj" ] Creating command line "link.exe @"c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\Debug\RSP0000492007500.rsp" /NOLOGO /ERRORREPORT:PROMPT" Output Window Compiling with CUDA Build Rule... "C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\bin\nvcc.exe" -gencode=arch=compute_10,code=\"sm_10,compute_10\" -gencode=arch=compute_20,code=\"sm_20,compute_20\" --machine 32 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.0\include" -maxrregcount=0 --compile -o "Debug/sample.cu.obj" sample.cu sample.cu sample.cu.obj : error LNK2019: unresolved external symbol _cudaLaunch@4 referenced in function "enum cudaError cdecl cudaLaunch(char *)" (??$cudaLaunch@D@@YA?AW4cudaError@@PAD@Z) sample.cu.obj : error LNK2019: unresolved external symbol ___cudaRegisterFunction@40 referenced in function "void __cdecl _sti_cudaRegisterAll_52_tmpxft_00001c68_00000000_8_sample_compute_10_cpp1_ii_b81a68a1(void)" (?sti__cudaRegisterAll_52_tmpxft_00001c68_00000000_8_sample_compute_10_cpp1_ii_b81a68a1@@YAXXZ) sample.cu.obj : error LNK2019: unresolved external symbol _cudaRegisterFatBinary@4 referenced in function "void __cdecl _sti_cudaRegisterAll_52_tmpxft_00001c68_00000000_8_sample_compute_10_cpp1_ii_b81a68a1(void)" (?sti__cudaRegisterAll_52_tmpxft_00001c68_00000000_8_sample_compute_10_cpp1_ii_b81a68a1@@YAXXZ) sample.cu.obj : error LNK2019: unresolved external symbol _cudaGetDeviceProperties@8 referenced in function _main sample.cu.obj : error LNK2019: unresolved external symbol _cudaGetDeviceCount@4 referenced in function _main sample.cu.obj : error LNK2019: unresolved external symbol _cudaConfigureCall@32 referenced in function _main C:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\Debug\god.exe : fatal error LNK1120: 7 unresolved externals Results Build log was saved at "file://c:\Users\t-sudhk\Documents\Visual Studio 2008\Projects\god\god\Debug\BuildLog.htm" god - 8 error(s), 0 warning(s) I will be highly obliged if someone could help me. Thanks

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  • How can I properly implement inetcpl.cpl as an external dll?

    - by Kyt
    I have the following 2 sets of code, both of which produce the same results: using System.Linq; using System.Runtime.InteropServices; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ResetIE { class Program { [DllImport("InetCpl.cpl", SetLastError=true, CharSet=CharSet.Unicode, EntryPoint="ClearMyTracksByProcessW")] public static extern long ClearMyTracksByProcess(IntPtr hwnd, IntPtr hinst, ref TargetHistory lpszCmdLine, FormWindowState nCmdShow); static void Main(string[] args) { TargetHistory th = TargetHistory.CLEAR_TEMPORARY_INTERNET_FILES; ClearMyTracksByProcessW(Process.GetCurrentProcess().Handle, Marshal.GetHINSTANCE(typeof(Program).Module), ref th, FormWindowState.Maximized); Console.WriteLine("Done."); } } and ... static class NativeMethods { [DllImport("kernel32.dll")] public static extern IntPtr LoadLibrary(string dllToLoad); [DllImport("kernel32.dll")] public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName); [DllImport("kernel32.dll")] public static extern bool FreeLibrary(IntPtr hModule); } public class CallExternalDLL { [UnmanagedFunctionPointer(CallingConvention.Cdecl)] public delegate long ClearMyTracksByProcessW(IntPtr hwnd, IntPtr hinst, ref TargetHistory lpszCmdLine, FormWindowState nCmdShow); public static void Clear_IE_Cache() { IntPtr pDll = NativeMethods.LoadLibrary(@"C:\Windows\System32\inetcpl.cpl"); if (pDll == IntPtr.Zero) { Console.WriteLine("An Error has Occurred."); } IntPtr pAddressOfFunctionToCall = NativeMethods.GetProcAddress(pDll, "ClearMyTracksByProcessW"); if (pAddressOfFunctionToCall == IntPtr.Zero) { Console.WriteLine("Function Not Found."); } ClearMyTracksByProcessW cmtbp = (ClearMyTracksByProcessW)Marshal.GetDelegateForFunctionPointer(pAddressOfFunctionToCall, typeof(ClearMyTracksByProcessW)); TargetHistory q = TargetHistory.CLEAR_TEMPORARY_INTERNET_FILES; long result = cmtbp(Process.GetCurrentProcess().Handle, Marshal.GetHINSTANCE(typeof(ClearMyTracksByProcessW).Module), ref q, FormWindowState.Normal); } } both use the following Enum: public enum TargetHistory { CLEAR_ALL = 0xFF, CLEAR_ALL_WITH_ADDONS = 0x10FF, CLEAR_HISTORY = 0x1, CLEAR_COOKIES = 0x2, CLEAR_TEMPORARY_INTERNET_FILES = 0x8, CLEAR_FORM_DATA = 0x10, CLEAR_PASSWORDS = 0x20 } Both methods of doing this compile and run just fine, offering no errors, but both churn endlessly never returning from their work. The PInvoke code was ported from the following VB, which was fairly difficult to track down: Option Explicit Private Enum TargetHistory CLEAR_ALL = &HFF& CLEAR_ALL_WITH_ADDONS = &H10FF& CLEAR_HISTORY = &H1& CLEAR_COOKIES = &H2& CLEAR_TEMPORARY_INTERNET_FILES = &H8& CLEAR_FORM_DATA = &H10& CLEAR_PASSWORDS = &H20& End Enum Private Declare Function ClearMyTracksByProcessW Lib "InetCpl.cpl" _ (ByVal hwnd As OLE_HANDLE, _ ByVal hinst As OLE_HANDLE, _ ByRef lpszCmdLine As Byte, _ ByVal nCmdShow As VbAppWinStyle) As Long Private Sub Command1_Click() Dim b() As Byte Dim o As OptionButton For Each o In Option1 If o.Value Then b = o.Tag ClearMyTracksByProcessW Me.hwnd, App.hInstance, b(0), vbNormalFocus Exit For End If Next End Sub Private Sub Form_Load() Command1.Caption = "??" Option1(0).Caption = "?????????????" Option1(0).Tag = CStr(CLEAR_TEMPORARY_INTERNET_FILES) Option1(1).Caption = "Cookie" Option1(1).Tag = CStr(CLEAR_COOKIES) Option1(2).Caption = "??" Option1(2).Tag = CStr(CLEAR_HISTORY) Option1(3).Caption = "???? ???" Option1(3).Tag = CStr(CLEAR_HISTORY) Option1(4).Caption = "?????" Option1(4).Tag = CStr(CLEAR_PASSWORDS) Option1(5).Caption = "?????" Option1(5).Tag = CStr(CLEAR_ALL) Option1(2).Value = True End Sub The question is simply what am I doing wrong? I need to clear the internet cache, and would prefer to use this method as I know it does what I want it to when it works (rundll32 inetcpl.cpl,ClearMyTracksByProcess 8 works fine). I've tried running both as normal user and admin to no avail. This project is written using C# in VS2012 and compiled against .NET3.5 (must remain at 3.5 due to client restrictions)

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  • Reference a GNU C (POSIX) DLL built in GCC against Cygwin, from C#/NET

    - by Dale Halliwell
    Here is what I want: I have a huge legacy C/C++ codebase written for POSIX, including some very POSIX specific stuff like pthreads. This can be compiled on Cygwin/GCC and run as an executable under Windows with the Cygwin DLL. What I would like to do is build the codebase itself into a Windows DLL that I can then reference from C# and write a wrapper around it to access some parts of it programatically. I have tried this approach with the very simple "hello world" example at http://www.cygwin.com/cygwin-ug-net/dll.html and it doesn't seem to work. #include <stdio.h> extern "C" __declspec(dllexport) int hello(); int hello() { printf ("Hello World!\n"); return 42; } I believe I should be able to reference a DLL built with the above code in C# using something like: [DllImport("kernel32.dll")] public static extern IntPtr LoadLibrary(string dllToLoad); [DllImport("kernel32.dll")] public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName); [DllImport("kernel32.dll")] public static extern bool FreeLibrary(IntPtr hModule); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate int hello(); static void Main(string[] args) { var path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "helloworld.dll"); IntPtr pDll = LoadLibrary(path); IntPtr pAddressOfFunctionToCall = GetProcAddress(pDll, "hello"); hello hello = (hello)Marshal.GetDelegateForFunctionPointer( pAddressOfFunctionToCall, typeof(hello)); int theResult = hello(); Console.WriteLine(theResult.ToString()); bool result = FreeLibrary(pDll); Console.ReadKey(); } But this approach doesn't seem to work. LoadLibrary returns null. It can find the DLL (helloworld.dll), it is just like it can't load it or find the exported function. I am sure that if I get this basic case working I can reference the rest of my codebase in this way. Any suggestions or pointers, or does anyone know if what I want is even possible? Thanks. Edit: Examined my DLL with Dependency Walker (great tool, thanks) and it seems to export the function correctly. Question: should I be referencing it as the function name Dependency Walker seems to find (_Z5hellov)? Edit2: Just to show you I have tried it, linking directly to the dll at relative or absolute path (i.e. not using LoadLibrary): [DllImport(@"C:\.....\helloworld.dll")] public static extern int hello(); static void Main(string[] args) { int theResult = hello(); Console.WriteLine(theResult.ToString()); Console.ReadKey(); } This fails with: "Unable to load DLL 'C:.....\helloworld.dll': Invalid access to memory location. (Exception from HRESULT: 0x800703E6) *Edit 3: * Oleg has suggested running dumpbin.exe on my dll, this is the output: Dump of file helloworld.dll File Type: DLL Section contains the following exports for helloworld.dll 00000000 characteristics 4BD5037F time date stamp Mon Apr 26 15:07:43 2010 0.00 version 1 ordinal base 1 number of functions 1 number of names ordinal hint RVA name 1 0 000010F0 hello Summary 1000 .bss 1000 .data 1000 .debug_abbrev 1000 .debug_info 1000 .debug_line 1000 .debug_pubnames 1000 .edata 1000 .eh_frame 1000 .idata 1000 .reloc 1000 .text Edit 4 Thanks everyone for the help, I managed to get it working. Oleg's answer gave me the information I needed to find out what I was doing wrong. There are 2 ways to do this. One is to build with the gcc -mno-cygwin compiler flag, which builds the dll without the cygwin dll, basically as if you had built it in MingW. Building it this way got my hello world example working! However, MingW doesn't have all the libraries that cygwin has in the installer, so if your POSIX code has dependencies on these libraries (mine had heaps) you can't do this way. And if your POSIX code didn't have those dependencies, why not just build for Win32 from the beginning. So that's not much help unless you want to spend time setting up MingW properly. The other option is to build with the Cygwin DLL. The Cygwin DLL needs an initialization function init() to be called before it can be used. This is why my code wasn't working before. The code below loads and runs my hello world example. //[DllImport(@"hello.dll", EntryPoint = "#1",SetLastError = true)] //static extern int helloworld(); //don't do this! cygwin needs to be init first [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)] static extern IntPtr GetProcAddress(IntPtr hModule, string procName); [DllImport("kernel32", SetLastError = true)] static extern IntPtr LoadLibrary(string lpFileName); public delegate int MyFunction(); static void Main(string[] args) { //load cygwin dll IntPtr pcygwin = LoadLibrary("cygwin1.dll"); IntPtr pcyginit = GetProcAddress(pcygwin, "cygwin_dll_init"); Action init = (Action)Marshal.GetDelegateForFunctionPointer(pcyginit, typeof(Action)); init(); IntPtr phello = LoadLibrary("hello.dll"); IntPtr pfn = GetProcAddress(phello, "helloworld"); MyFunction helloworld = (MyFunction)Marshal.GetDelegateForFunctionPointer(pfn, typeof(MyFunction)); Console.WriteLine(helloworld()); Console.ReadKey(); } Thanks to everyone that answered~~

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