Thread: Big problems with the Text function

Hi!

I have huge problems with this (Text) function and the strlen function. When I use them together the exception is thrown when I run the program in the DEBUG configuration manager. In the RELEASE c.m. everything is OK.

Code:

# define STPFILE "setup.cfg"

typedef struct
{
    char LanguageFile[30];
 } Setup;

char *ReadLanguage () // function reads a language file from the file "setup.cfg"
{
    FILE *fin = NULL;
    Setup file;

    if ((fin = fopen (STPFILE, "rb")) != NULL)
    {
        fread (&file, sizeof (Setup), 1, fin);
	fclose (fin);	
	return file.LanguageFile;
    }
    else return NULL;
}

char *Text (char File[], short Line)
{
    FILE *fin = NULL;
    short Lines = 0, UC = 0;
    char Character, *Text1 = NULL, *temp = NULL;

    if ((fin = fopen (File, "rt")) != NULL)
    {
        Text1 = malloc (sizeof (char) * 100);
	if (Text1 == NULL) exit (1);	
        temp = Text1;
	while (fscanf (fin, "%c", &Character) != EOF)
	{
	    if (Character == '#') Lines++; // counting lines
	    if (Lines == Line)
	    {
	        if (Character != '\n')
		{
		    UC++;
		}
		if (UC >= 8)
		{
		    if ( (Character == ';') || (Character == '\n') ) break;
		    *(temp++) = Character;
		}
	    }
        }
        *temp = 0;
        fclose (fin);
        return Text1;
    }
    else
    {
        return NULL;
    }
}

Text and strlen function together:

Code:

char *Text1 = Text (ReadLanguage (), 1); // functions "Text" and ReadLanguage() are called.
// Function Text reads the first line in the "ReadLanguage ()" file
short Text1Length = (short) strlen (Text1) + 1; <- here is thrown the exception

This is what I get in .NET:
" Unhandled exception at 0x00419d10 in Text.exe: 0xC0000005: Access violation reading location 0x00000000. "

But when I use strlen in a different way, something like this, everything is OK (in the DEBUG c.m.).

Code:

short Text1Length = 0;
Text1Length = (short) strlen ("HELLO") + 1; <- the exception is not thrown

What could be wrong? Is it the Text function?
I would be very grateful for your answers.
I'm using Visual Studio C++.NET on Win2k.

I tried to print out the file that it reads from the setup.cfg file and it came out that it is null. But this only happens when I have a DEBUG c.m. In the RELEASE c.m. I get the file printed on the screen (it's not the junk filename). I looked the options of the DEBUG but I have all the directorys well written. I really don't get it. And Salem, the file "setup.cfg" is a binary file.

Like Salem, said your probably referencing a pointer that is NULL. I'd suggest using the poor mans debugger (printf), and print out the value of some of the pointers your passing around. Then play Spot The NULL One In The Wrong Place.

use printf like this:
>printf ("ptr is %p", ptr);

Also, you said the file is binary, but you opened it with "rt".

The file "setup.cfg" is binary. The path to the file which is written in the "setup.cfg" file is a text file and it is opened with mode "rt".

EDIT:

Why is everything OK when I run the program in the RELEASE c.m?

Suggest putting a printf here:

Code:

....
 }
    else
    {
        printf("File Open Failed! %s\n", File); /* <--- put this in */
        return NULL;
        }
}

Can anyone explain to me WHY is the program working when I run it as a RELEASE??

does it run from 2 different directories?

Shiro:
>You have to declare and allocate a new piece of memory and return the pointer of that
Isn't that being done here:

Code:

        Text1 = malloc (sizeof (char) * 100);
	if (Text1 == NULL) exit (1);	
        temp = Text1;
	while (fscanf (fin, "%c", &Character) != EOF)
	{
	    if (Character == '#') Lines++; // counting lines
	    if (Lines == Line)
	    {
	        if (Character != '\n')
		{
		    UC++;
		}
		if (UC >= 8)
		{
		    if ( (Character == ';') || (Character == '\n') ) break;
		    *(temp++) = Character;
		}
	    }
        }
        *temp = 0;
        fclose (fin);
        return Text1;

As to the why, it sounds like a Mandelbug, I'm surprised this hasn't been posed by Prelude, who I'm sure has "C Unleashed" memorized.

"The program works 70% of the time (for given inputs), or only works outside the debugger...."

It goes onto describe this type of bug as "the reverse of the Heisenbug". These it appears are usually memory violations... "either some pointer is pointing somewhere it shouldn't, or some array index is wrong"

I know this probably doesn't tell most of the readers of this thread anything they don't already know, but I found the read interesting, and I love trivia. Anyhow, a possible answer would be, that when your debugger is running, the memory your code allocates is unsafe, but when your debugger isn't running, the memory your program allocates is safe. A very untrustworthy situation long term.

This bug is a pain in the ass. Do the strncpy, strcpy and strcat functions add the '\0' at the end of the string?

Now I'm trying with printf's to detect the bug but I just can't find it. Anyone knows how to use the debugger in the .NET studio?

Based on your code in your first post:

Code:

#define STPFILE setup.cfg

typedef struct 
{
	char	LanguageFile[30];
} Setup;

char *ReadLanguage(void);
char *Text(char[] , short);

/* */
char *ReadLanguage(void)	// function reads a language file from the file "setup.cfg"
{
	FILE	*fin = NULL;
	Setup	file;
	if ((fin = fopen(STPFILE, "rb")) != NULL)
	{
	.........................

The bold parts don't work, because you haven't surrounded the filename in quotes. The compiler preprocessor will resolve this to
>if ((fin = fopen(setup.cfg, "rb")) != NULL)
which is incorrect, it should be
>if ((fin = fopen("setup.cfg", "rb")) != NULL)

So to resolve, change to #define to
>#define STPFILE "setup.cfg"