File Opening Throws a Illegal Op.

**Crossbow** · 08-10-2004

Hello,
I haven't programmed in a while and I am trying to make a simple flashcard type program to drill myself on a foreign language.

However for the open file function, to open the flashcard text files, it keeps throwing an Illegal Op. message in Kernel32.dll. Here is the function, which I know is where the problem is at least occuring, if not the only place with trouble.

Specifically I have narrowed the fault down to the last fseek() function, if that helps.

Code:

 
void OpenCards(HWND hwnd, char *filename)
{
               FILE *file = NULL;
			   fpos_t length = 0;
			   char *buff = NULL;

			   file = fopen(filename,"rt");
					if(!file)
					{
						MessageBox(hwnd,"Couldn't load file!","Error",MB_OK | MB_ICONERROR);
						return;
					}
				fseek(file,0,SEEK_END);
				fgetpos(file,&length);

				buff = new char[(int)length + 1];
					if(!buff)
					{
						MessageBox(hwnd,"Couldn't load OurFile.txt","Error",MB_OK | MB_ICONERROR);
      						return;
					}
			    fseek(file,0,SEEK_SET); //this is where the fault is
                fread(buff,(int)length,1,file);
				buff[(int)length] = NULL;
				fclose(file);
    ProcessCards(hwnd, buff);
}

**Codeplug** · 08-10-2004

If fopen() is blow'n chow then "filename" must be a bad pointer.

Or maybe it's all those TAB characters in your source code

gg

**bigtamscot** · 08-10-2004

try these changes...

Code:

if((file = fopen(filename,"rt")) == NULL)
{
	MessageBox(hwnd,"Couldn't load file!","Error",MB_OK | MB_ICONERROR);
						return;
}
fseek(file,0,SEEK_END);
length = ftell(filename);

**glUser3f** · 08-10-2004

Mode in fopen should be "r", not "rt":

Code:

file = fopen(filename, "r")

**Codeplug** · 08-10-2004

There is nothing wrong with "t" as long as it isn't the first mode character seen and you're using the MS C standard lib fopen().

You should be using ftell() instead of fgetpos(). The fpos_t type is only defined for use by fgetpos() and fsetpos(). For instance, a standard lib implementation is free to make fpos_t a structure. In this case, it's an __int64 so your posted code won't have problems until the size of the file exceeds the largest value for a signed int.

You should also be:
- delete[]'ing that memory when your done with it!!
- calling fclose() before return statements
- checking return values of fseek(), fgetpos()/ftell(), and fread()
- learning how to use <fstream>

gg

**glUser3f** · 08-10-2004

Originally Posted by Codeplug

There is nothing wrong with "t" as long as it isn't the first mode character seen and you're using the MS C standard lib fopen().

Hmm, thanks for the info, "t" isn't in the C standard, and I didn't know that MS C lib contains it.

**Crossbow** · 08-11-2004

Thanks everybody, I got it to load correctly now, I guess the fgetpos( was doing something screwy, but I really have no idea. Anyway, thanks again.

**Hunter2** · 08-11-2004

Is this program is in C++ (the thread is in the C++ forum)? If so, why not use a std::ifstream?

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