Compile error

[843]

Could someone please tell me what's wrong with this code snippet? It runs perfectly well when compiled with MinGW, but selecting 'f' crashes the program when it is compiled with VS2010. I wasn't able to isolate the bug, but the files aren't removed or renamed.

		case 'f':
			case 'F':
			write(); //calls write() if (f) is selected

			/* verifies file closure */
            if (fclose(f) != 0 || fclose(f_old) != 0)
            {
                printf("\nFile close error.");
                return 1; //return error message
            }

			/* replaces original document with new one */
			remove("database.txt"); //deletes original document
			rename("database_temp.txt", "database.txt"); //renames document
					
			return 0; //program exits normally

			default: //returns error message if input is none of the above
			printf("Invalid input.\n");

Here's the write() function:

int write ()
{
	int i; //declares counter

    /* cycles each seat variable to file */
    for (i = 1; i <= 30; i++)
    fprintf(f, "%s\n%s\n%s\n\n",
            seat[i].no, seat[i].fname, seat[i].lname);

	return 0; //returns to main function
}

[claudiu]

What is the error?

There is another function in the library called write() so that is probably why it is complaining. Change the name of the function.

[843]

I tried changing the function name but to no avail. I think the problem is compiler-specific, otherwise MinGW would have complained as well.

Problem signature:
Problem Event Name: APPCRASH
Application Name: 2.exe
Application Version: 0.0.0.0
Application Timestamp: 4cfd0be9
Fault Module Name: ntdll.dll
Fault Module Version: 6.1.7600.16559
Fault Module Timestamp: 4ba9b21e
Exception Code: c0000005
Exception Offset: 00046bf0
OS Version: 6.1.7600.2.0.0.256.1
Locale ID: 1033
Additional Information 1: 0a9e
Additional Information 2: 0a9e372d3b4ad19135b953a78882e789
Additional Information 3: 0a9e
Additional Information 4: 0a9e372d3b4ad19135b953a78882e789

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[CommonTater]

First off... putting code in switch statements is a BAD idea. Declaring variables in switch cases is an even bigger recipe for disaster. It makes debugging near impossible. It is far better to write functions to do these tasks and then call the function from the switch statement.

int write ()
{
	int i; //declares counter

    /* cycles each seat variable to file */
    for (i = 1; i <= 30; i++)
    fprintf(f, "%s\n%s\n%s\n\n",
            seat[i].no, seat[i].fname, seat[i].lname);

	return 0; //returns to main function
}

Since you are not returning any useful information here, you should redeclare the write function as void write(void) and remove the return statement.

Also it looks like you have the paramters for your rename() call backwards...

[Bayint Naung]

Have you tried to debug using debugger yet?

 fprintf(f, "%s\n%s\n%s\n\n",
            seat[i].no, seat[i].fname, seat[i].lname);

Is f a valid FILE pointer?
What about seat[i] ? Is sear[i].no integer or string?
In C, for an array a[N], valid indices are 0-N-1.
In your loop it's for(i = 1; i <= 30 ;i++)

[843]

Thanks for all the feedback. How do you exit a function in the middle of a code if the type is void?

I haven't learned how to use a debugger yet, but the program works perfectly when compiled with MinGW. As for the loop condition, I started with 1 as seat[0] is empty due to certain seat arrangements.

As for rename(), its argument is (old_name, new_name) right?

[tabstop]

1) "return;" is still valid in a void function.

2) MinGW and VC use different run-time libraries, and just in general do things differently. It is not at all surprising or uncommon (in fact it is very common) for an incorrect program to crash in one and just do something odd (or, worse, something that looks correct) in the other. Bayint's suggestion about checking your loop bounds ("i <= 30") looks like a very good place to start to me.

[843]

Except for the initialization, which includes 0, every single loop that cycles through the array variables uses the same condition. I'm not sure if there's anything else I can check.

[CommonTater]

1) "return;" is still valid in a void function.

But return 0; is not.

[843]

I renamed the file pointer from f to f_new and it worked!

Any idea why?

[anduril462]

Probably because you're using icky global variables and you perhaps have multiple variables called f with different scopes and write isn't using the one you think it's using. Just a guess though, based on what code you did post.