Visual Basic, Bad DLL calling convention (error 49)

Bad DLL calling convention (error 49)

Author	Message
Ioannis Demetriade #1 / 4	Bad DLL calling convention (error 49) Hi, I am trying to call a DLL function that I wrote in C++ and I keep getting error 49 - Bad DLL calling convention. The DLL function expects a pointer to a null terminated string and returns an integer. extern "C" __declspec(dllexport) int SetStreamDate(char *date) { ... return 10; Quote: } This is how i declared the DLL function in VB: Private Declare Function SetStreamDate Lib MyLib.dll" (ByVal mDate As String) As Long The function is called in the following way: Dim mDate As String ... mDate = Format(Now, "yyyy-mm-dd") k = SetStreamDate(ByVal mDate) The problem is that when I am debugging the application I get error 49 on the line that calls the DLL function whereas if i compile the app into an exe there is no problem at all. (I have no problem calling any other DLL function from the same DLL). Thanks Ioannis
Tue, 08 Jun 2004 21:37:09 GMT

J Fren #2 / 4	Bad DLL calling convention (error 49) 1) are you sure that you are using the StdCall parameter passing convention for getting the parameters in C ? 2) If it works when compiled, but not in the IDE then have you checked that you do not have two copies of the DLL - VB is a bit dim about this - it searches different paths in the IDE than in compiled mode. 3) Watch out for regional variations from Format - it is horribly locale aware. On Fri, 21 Dec 2001 15:37:09 +0200, "Ioannis Demetriades" Quote: >Hi, >I am trying to call a DLL function that I wrote in C++ and I keep getting >error 49 - Bad DLL calling convention. The DLL function expects a pointer to >a null terminated string and returns an integer. >extern "C" __declspec(dllexport) int SetStreamDate(char *date) >{ > ... > return 10; >} >This is how i declared the DLL function in VB: >Private Declare Function SetStreamDate Lib MyLib.dll" (ByVal mDate As >String) As Long >The function is called in the following way: >Dim mDate As String >... >mDate = Format(Now, "yyyy-mm-dd") >k = SetStreamDate(ByVal mDate) >The problem is that when I am debugging the application I get error 49 on >the line that calls the DLL function whereas if i compile the app into an >exe there is no problem at all. (I have no problem calling any other DLL >function from the same DLL). >Thanks >Ioannis
Tue, 08 Jun 2004 23:12:59 GMT

Kristof Meirla #3 / 4	Bad DLL calling convention (error 49) hi, On Fri, 21 Dec 2001 15:37:09 +0200, "Ioannis Demetriades" Quote: >Hi, >I am trying to call a DLL function that I wrote in C++ and I keep getting >error 49 - Bad DLL calling convention. The DLL function expects a pointer to >a null terminated string and returns an integer. >extern "C" __declspec(dllexport) int SetStreamDate(char date) use extern "C" __declspec(dllexport) int __stdcall SetStreamDate(char date); and declare SetStreamDate in the .def file of your C++ project BR, Kristof Meirlaen -- Is your server up? Are you sure? Monitor your servers: http://www.kri-soft.be/servermonitor/
Wed, 09 Jun 2004 02:27:59 GMT

Ioannis Demetriade #4 / 4	Bad DLL calling convention (error 49) Wrong declaration of the exported functions! VB does not support DLL functions declared with __declspec(dllexport) . It can access the functions but it you start adding arguments to the DLL functions, those arguments will not be pushed in/popped out of the stack correctly. This is the correct function declaration in VC++ (so that the functions can be accessed correctly from VB) int __stdcall SetStreamDate(char *date)
Wed, 09 Jun 2004 17:27:59 GMT

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