Assertion Error

[tao]

I'm back again, with another fgets issue (sort of).

I've used this code numerous times, as it's quite standard, but for some reason I'm getting an error now.

Debug Assertion Failed
File: fgets.c
Line: 60

Expression: str != NULL

And the parcel of code giving me the error (actually, I isolated it to just the while(fgets()!=NULL) loop - the code inside the loop has no influence).

FILE *cFile;
char Line[100];

// Check for match before opening file
if(strcmp(STRTOCOMP1, STRTOCOMP2) == 0)
{
	cFile = fopen(FILENAME, "r");

	// If the file cannot be read, warn the user
	if(!inp)
	{
		MessageBox(Msg, "Error", MB_OK | MB_ICONEXCLAMATION);
		return;

	// If the file can be read, proceed to read it in
	} else
	{
		while(fgets(Line, sizeof Line, cFile) != NULL)
		{
			// sscanf() stuff to a struct vector
		}

		fclose(cFile);
	}

	// If there was no match, warn the user
} else
{
	MessageBox(Msg, "Error", MB_OK);
}

The code seems flawless -- why would it be throwing an assertion error? Unless I'm missing something completely obvious, which is kind of why I'm asking for help.

[Tonto]

Can you post the actual code with str and inp and stuff?

[Salem]

	cFile = fopen(FILENAME, "r");

	// If the file cannot be read, warn the user
	if(!inp)

Helps if you check the actual variable, not something else.

> Expression: str != NULL
It's basically telling you that a parameter which should be != NULL is in fact failing that test (ie, it is NULL).

[tao]

I found that this morning when I took a fresh look at the code. Thanks for the let-know, though. Funny how something so menial can slip me by so easily.

[tao]

I have another question regarding sscanf as part of the above code; thought I'd throw it in here as opposed to cluttering up the place with a new thread.

I'm trying to read in a file and parse the lines with sscanf, but for some reason when I do the assignment the variables are all assigned the same parse snippet.

Below is the code involved:

struct ConfigFile
{
	int Label;
	CString STR1;
	CString STR2;
	CString STR3;
} Temp;

std::vector <ConfigFile> vConfig;

while(fgets(Line, sizeof Line, cFile) != NULL)
{
	if ( sscanf(Line, "%d %s %s %s", &Temp.Label, Temp.STR1, Temp.STR2, Temp.STR3) == 4)
		vConfig.push_back(Temp);
}

The file contains a three-digit int, followed by three strings (simple strings with no spaces), all divided by whitespace (tabs or spaces only).

ex.
123 STRING1 STRING2 STRING3
256 STRING4 STRING5 STRING6
etc.

My output is giving me:
123
STRING3
STRING3
STRING3

CStrings STR1, STR2, STR3, they are all being assigned the same value for some reason. I have absolutely no idea why; but I'm rather new at much of this, so that isn't surprising.

Anybody have any suggestions / solutions? Thanks.

[Tonto]

Strange feeling that scanf can not work with CString's.

[Salem]

> CStrings STR1, STR2, STR3, they are all being assigned the same value for some reason
Because %s only knows about char arrays, not CStrings.
I've no idea what they are, probably some locally defined C++ class perhaps?
So why aren't you using getline() and string streams to extract information?

Use local arrays, like so, if you insist on sscanf

	char t1[100], t2[100], t3[100];
	if ( sscanf(Line, "%d %s %s %s", &Temp.Label, t1, t2, t3) == 4) {
		Temp.STR1 = t1;
		Temp.STR2 = t2;
		Temp.STR3 = t3;
		vConfig.push_back(Temp);
	}

That is, assuming that your Cstring class has an overloaded assignment operator which does the right thing...

[tao]

I was wondering if it was perhaps the CString type that was causing conflict. I'll try your suggestion, Salem.

Edit: Yes, that worked like a charm. Thanks for the input. =]

As to why I chose sscanf as opposed to getline, I felt it was a faster way to parse the data instead of manually skipping whitespace (since the data file has a predefined structure, I don't really require a lot of error checking).