Help with exporting to a dll

[namooth]

Hey all,
I'm trying to export some of my functions to dll and im having some trouble.

how i created my dll and lib:

// Define DllExport to declare exported symbols.
#define DllExport __declspec( dllexport )
 DllExport __declspec( dllexport )
 
 

#include <stdio.h>
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include  <commctrl.h>

typedef struct
{
    char secnum[8];
    char xnum[8];
    char xfirst[10];
    char xlast[10];
    char xage[3];
    char xaddress[10];
    char xphone[10];
}Item;

typedef struct phonebook  
{
    char num[4];
    char first_name[10];
    char last_name[10];
    char age[3];
    char address[10];
    char phone[10];
    
} PB;
 
DllExport int adde (int x, int y)
{
    return  (x+y);
}

DllExport int Refresh(FILE *f1,Item ListItem[])
{

  char str2[4];
  int x=0,y=1;
  PB p;
  rewind(f1); 
  
   while  (fread(&p, sizeof(PB), 1, f1)) 
                       {
                         itoa (y,str2,10);
                         strcpy(ListItem[x].secnum,p.num);
                         strcpy(ListItem[x].xnum,str2);
                         strcpy(ListItem[x].xfirst,p.first_name);
                         strcpy(ListItem[x].xlast,p.last_name);
                         strcpy(ListItem[x].xage,p.age);
                         strcpy(ListItem[x].xaddress,p.address);
                         strcpy(ListItem[x].xphone,p.phone);
                         x++;
                         y++;
                        }                                       
  return x;
}

my def file:

EXPORTS
adde
Refresh

my c file:

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
     {
......
int t=-1;
typedef int  (CALLBACK *MYPROC)(int);
typedef int  (CALLBACK *MYPROC2)(FILE*, Item*);
HINSTANCE hinstLib; 
MYPROC ProcAdd; 
MYPROC2 ProcAdd2; 
int fRunTimeLinkSuccess;

....
}

          case WM_COMMAND :
.......
 			  hinstLib = LoadLibrary("MyProj.dll");

			  if (hinstLib != NULL) 
				{ 
    
					ProcAdd = (MYPROC) GetProcAddress(hinstLib, "adde");
					if (fRunTimeLinkSuccess = (ProcAdd != NULL)) 
					bla = ProcAdd (4,4); // Works! bla is now 8
					FreeLibrary(hinstLib); 
.......
	hinstLib = LoadLibrary("MyProj.dll");
              if (hinstLib != NULL) 
                { 
                    ProcAdd2 = (MYPROC2) GetProcAddress(hinstLib, "Refresh");
                    if (fRunTimeLinkSuccess = (ProcAdd2 != NULL)) 
                    t=ProcAdd2 (poi,ListItem); // Doesn't work
                    FreeLibrary(hinstLib); 

}

The function "adde" works fine so im guessing the dll is ok but "Refresh" has a problem.
i don't know if

t=ProcAdd2 (poi,ListItem);

isn't being executed or that nothing is being returned to "t".
For some reason i can't debug it , as if the code stops at the line

t=ProcAdd2 (poi,ListItem)

I can debug before that line but if for example i add this line:

MessageBox(hwnd, "Test", "Test", MB_OK);

after

 t=ProcAdd2 (poi,ListItem);

I won't see the popup.

Thanks

 

[joel76]

You can put debug (MessageBox(hwnd, "Test", "Test", MB_OK) in the code of the Dll to see where it doesn't work.
poi is initialized ?

 

[namooth]

yes, poi is initialized .
Refresh works fine without the dll so it's something i did wrong on the way.. the "adde" functions works great in the dll so it's not the dll build.

 

[joel76]

How do you initialized ListItem ?
What is its size ?

 

[namooth]

I've tried to find what's wrong in the last 12 hours.. here's my code:

http://dl.dropbox.com/u/17838/code/code.c

how i created the dll & lib:

http://dl.dropbox.com/u/17838/code/MyProj.CPP

http://dl.dropbox.com/u/17838/code/MyProj.def

I'm trying to return a value to "t" in line 540:

t = ProcAdd2 (poi,ListItem);

My code is linked to the lib file and the adde function works in the dll.
I've tried to remove the LoadLibrary completly and call the function like this:

t=Refresh(poi,ListItem);

but that gave me other errors.. though i would love to use that method instead of creation new MYPROC all the time.

Thanks

 

[joel76]

Your code is potentially dangerous.
You should use strncpy(ListItem[x].secnum,p.num, sizeof( ListItem[x].secnum)); instead of strcpy(ListItem[x].secnum,p.num);

Did you test your code in a simple console program, not in a dll ?

 

[namooth]

not in a dll my program runs great.

 

[joel76]

I tested your program on Visual Studio 2008

I made changes :

typedef int   (*MYPROC)(int, int);
typedef int   (*MYPROC2)(FILE*, Item*);

You had a problem between "__declspec( dllexport )" and CALLBACK.

I change also, as I told you,

     strncpy(ListItem[x].secnum,p.num, sizeof(p.num));
     strncpy(ListItem[x].xnum,str2, strlen(str2));
     strncpy(ListItem[x].xfirst,p.first_name, sizeof(p.first_name));
     strncpy(ListItem[x].xlast,p.last_name, sizeof(p.first_name));
     strncpy(ListItem[x].xage,p.age, sizeof(p.age));
     strncpy(ListItem[x].xaddress,p.address, sizeof(p.address));
     strncpy(ListItem[x].xphone,p.phone, sizeof(p.phone));

and it works !

The data file was initialized with

	PB p[] = {  {"001", "first1   ", "martin   ", "29", "123456789", "123456789"},
				{"002", "first2   ", "martin   ", "28", "123456789", "123456789"},
				{"003", "first3   ", "martin   ", "52", "123456789", "123456789"},
				{"004", "first4   ", "martin   ", "43", "123456789", "123456789"}};

	poi = fopen("C:\\Travail\\Developpements\\Visual Studio\\C\\TestDll\\toto.txt", "w");

	fwrite(p, sizeof(PB), 4, poi);

	fclose(poi);

 

[namooth]

doesn't work for me
i made your changes

 typedef int   (*MYPROC)(int, int);
typedef int   (*MYPROC2)(FILE*, Item*);

in code.c

and the other ones in the cpp file, created the dll & lib, moved them to my project but when i press on delete stull nothing happens.
Have u managed to run the c code and to see the the ListView is updating live after u click the button "Delete"?

 

[namooth]

btw,
if i leave the code under WM_COMMAND i get this error:

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.

 

[joel76]

I must say that I did a C program, not C++ and it works in console mode not GUI (that why you used CALLBACK I think), I used the Dll not the lib (but for that, I don't think this change anything).

 

[namooth]

i also use C and 2008 but with gui, and when i press Add i get the error above plus the refresh doesn't work for me

 

[joel76]

I'll try your code later, it's time to lunch (8 pm in France).

 

[joel76]

I tried your code, the difference with your project is that the code of the Dll was a C code (.c not .cpp).
I had to remove CALLBACK from the typedef of MYPROC and MYPROC2 in code.c.

I must say that I don't understand your code : why did you write a dll to fill the ListItem ? sometimes you use it and sometimes you don't.

I found something very strange and I can't explain, in code.c sizeof(Item) is 108 and in the Dll it's size is 59 that's why Refresh don't work.

 

[joel76]

I just found why, in code.c you have

typedef struct
{
	int  secnum[8];
	int  xnum[8];
	char xfirst[10];
	char xlast[10];
	char xage[3];
	char xaddress[10];
	char xphone[10];
}Item;

and in PyProj.cpp you have

typedef struct
{
    char  secnum[8];
    char  xnum[8];
    char xfirst[10];
    char xlast[10];
    char xage[3];
    char xaddress[10];
    char xphone[10];
}Item;

Read the first two lines of the struct !!!

 

[namooth]

Thanks for your help.
I changed the int in the first two lines to chat but im still getting "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. " when i run the code. When i start delete i still don't see the refresh in action:
"First-chance exception at 0x77a08c39 in BtnLook.exe: 0xC0000005: Access violation writing location 0x00000014.
The program '[6900] BtnLook.exe: Native' has exited with code 0 (0x0).

 

[joel76]

It's just calling convention, in your C program, test with and without CALLBACK in
typedef int (CALLBACK *MYPROC)(int);
typedef int (CALLBACK *MYPROC2)(FILE*, Item*);
and it should work.

 

[namooth]

i changed it again to:
typedef int (CALLBACK *MYPROC)(int, int);
typedef int (CALLBACK *MYPROC2)(FILE*, Item*);

im still getting the error "First-chance exception at 0x77a08c39 in BtnLook.exe: 0xC0000005: Access violation writing location 0x00000014.
The program '[5412] BtnLook.exe: Native' has exited with code 0 (0x0)."
when i press delete and nothing happens...

 

[joel76]

That's other thing, I told you that your code is potentially dangerous, change all your
strcpy(ListItem[x].xfirst,p.first_name);
in
strncpy(ListItem[x].xfirst,p.first_name, sizeof(p.first_name));

Maybe this can fix the bug.
You can use debug mode to find where it's happen.