Re: How do I stop a TSP written in Delphi crashing on Add Provider?

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In your "C" sample:

char mod[MAXMODULE];
....
GetModuleFileName((HMODULE)hLib, (LPTSTR)mod, MAXMODULE);

You cast mod to a pointer to TCHAR but you declare it a char.
--
Grant Schenck
http://grantschenck.tripod.com



"Paul Soper" <paul_soper@xxxxxxxxxxx> wrote in message
news:#XdtTgyTFHA.1600@xxxxxxxxxxxxxxxxxxxxxxx
> Hi everyone,
>
> I know this is not a general programming discussion about accessing DLLs,
> but I want to disclose
> my findings because this is TAPI related. I need help to check that I'm
not
> missing something stupid in my C code at the bottom of this post.
>
> If I use the Delphi code:
>
> -------------
>
> function TSPI_providerUIIdentify(var lpszUIDLLName : LPWSTR): Longint;
> stdcall; external 'PSTSP.DLL';
>
> procedure TForm1.Button1Click(Sender: TObject);
>
> var buffer : LPWSTR;
>
> begin
> GetMem(buffer, MAX_PATH);
> TSPI_providerUIIdentify(buffer);
> ShowMessage(' >' + WideCharToString(buffer) + '<');
> FreeMem(buffer);
> end;
>
> --------------
>
> Or, if I use the Visual Basic code:
>
> --------------
>
> Private Declare Function TSPI_providerUIIdentify Lib "PSTSP.DLL" (ByRef
> myString As Long) As Long
>
> Private Sub Command1_Click()
> Dim buffer As String
> Dim answer As Long
> Dim count As Integer
>
> 'Allocate 300 chars in to the String
> For count = 0 To 299
> buffer = buffer & "a"
> Next count
>
> answer = TSPI_providerUIIdentify(StrPtr(buffer))
>
> MsgBox buffer
> End Sub
>
> --------------
>
> all works fine in both cases and I get the correct name back in "buffer".
>
> But, if I use the C code (in a console application to keep it simple -
> Visual C creates masses of code that would complicate the example):
>
> --------------
>
> #include "stdafx.h"
> #include <windows.h>
> #include <iostream.h>
> #include <stdio.h>
> #include <conio.h>
> #include <stdlib.h>
> #include <malloc.h>
>
> #define MAXMODULE 300
>
> typedef LONG (WINAPI *cfunc)(LPWSTR lpzUIDLLName);
>
> cfunc myFunction;
> char mod[MAXMODULE];
> LPWSTR tspName;
> long theResult;
>
> /* very quick and dirty */
> int main(int argc, char* argv[])
> {
> HINSTANCE hLib = LoadLibrary("PSTSP.DLL");
>
> if(hLib == NULL) {
> cout << "Unable to load library!" << endl;
> getch();
> return 1;
> }
>
> GetModuleFileName((HMODULE)hLib, (LPTSTR)mod, MAXMODULE);
> cout << "Library loaded: " << mod << endl;
>
> myFunction = (cfunc) GetProcAddress((HMODULE)hLib,
> "TSPI_providerUIIdentify");
>
> if(myFunction == NULL) {
> cout << "Unable to get access to the function!" << endl;
> FreeLibrary((HMODULE)hLib);
> getch();
> return 1;
> }
>
> //malloc 2 bytes per char and 2 for the null
> tspName = (LPWSTR) malloc((MAX_PATH * 2) + 2);
>
> if(tspName == NULL) {
> cout << "Unable to allocate memory!" << endl;
> FreeLibrary((HMODULE)hLib);
> getch();
> return 1;
> }
> else {
> cout << "Press enter to call the function..." << endl;
> getch();
>
> theResult = myFunction(tspName);
>
> cout << tspName << endl;
>
> free(tspName);
> }
>
> FreeLibrary((HMODULE)hLib);
>
> cout << "Finished... Press enter to close the window." << endl;
> getch();
>
> return 0;
> }
>
> --------------
>
> It crashes in a similar way to TAPI when calling this function. Am I
missing
> something? (i.e. is my C code OK?). When running this I get the program
"has
> encountered a problem and needs to close". The error signature is ModName:
> kernel32.dll ModVer: 5.1.2600.2180 Offset: 0000 9e4f.
>
> I can successfully use the code above to access a functions in the Delphi
> DLL that print a message to the console, return a long, add two numbers
and
> return a result etc. The problem comes when I try and pass a pointer - for
> example a char*, if I declare my Delphi function signature like this
> function paultest(instring: PChar) : Longint; stdcall;
> I can read the value of instring and use it, obviously if I modify it,
this
> only modified the local copy (for non Delphi guys, declaring it like the
> above is pass by value). If I declare it like this
> function paultest(var instring: PChar) : Longint; stdcall;
> I cannot read it or write to it without experiencing a C Program crash
(var
> indicates pass by reference - basically give me a pointer). I have tried
> direct assignment and StrCopy etc to write, and reading is simply a case
of
> trying to writeln it out.
>
> Trying the var/no var scenario with an integer yields the following
results:
> 1. c: declare and pass an int, delphi: declare var parameter => crash
> 2. c: declare and pass an int, delphi: don't declare var => can read the
> int, but writing affects only the local copy
> 3. c: declare int and declare int* in external function signature, pass
&int
> delphi: declare var parameter => read and write (i.e. modify OK)
> 4. c: declare int and declare int* in external function signature, pass
&int
> delphi: don't declare var => delphi gets the int representation of the
> pointer (i.e. the address, modification only affects local variable).
>
> This is what I would have thought of as "correct behaviour" anyway.
>
> All of this indicates to me that there is some problem when trying to
access
> any "string" based pointers from Delphi. I think I know need to approach
> another relevent forum to get the answers I need, as this is no longer in
> the realm of TAPI.
>
> A note to Bram: your function in your code is decalred function
> TSPI_providerUIIdentify(lpszUIDLLName : LPWSTR) : LONG;
> stdcall; I don;t understand how this can actually be modifying the
> lpszUIDLLName. Can you confirm that this actually sets the value external
to
> DLL please?
>
> Thanks for everyone's help so far. I will report back if I solve this
> problem.
>
> Kind Regards
>
> Paul
>
>
>


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