General protection fault/stack fault

[rusty uts]

Well I had an assignment to sort an array of structures so i went about trying but always some strange fault come about. Now not only does the main program fail but also another program. What i want to know is that is it a problem in my code, or something else is happening?? Below are the two programs!!

#include<stdio.h>
#include<conio.h>
#include<string.h>
main()
{
	struct boy
	{
		char name[100];
		int marks;
	};
	struct boy a[100];
	int no,i,l,m,k,t;
	char nam[100];
	printf("Enter no of students");
	scanf("%d", &no);
	for(i=0;i<no;i++)
	{
		printf("Enter Name");
		gets(a[i].name);
		printf("Enter Marks");
		scanf("%d", a[i].marks);
	}
	for(l=1;i<=no-1;l++)
	{
		for(m=0;m<no-l;m++)
		{
			if(a[m].marks>a[m+1].marks)
			{
				strcpy(nam,a[m].name);
				strcpy(a[m].name,a[m+1].name);
				strcpy(a[m+1].name,nam);
				t=a[m].marks;
				a[m].marks=a[m+1].marks;
				a[m+1].marks=t;
			}
		}
	}
	for(k=0;k<no;k++)
	{
		puts(a[k].name);
		printf("%d", a[k].marks);
	}
	getch();
	return 0;
}

on running it it gives that "stack fault in module toolhelp.dll at 0001:2239"

Again the simple program to retrieve something from an array of structure fails saying "general protection exception 0x2557:0x37EB processor fault"

#include<stdio.h>
#include<conio.h>
main()
{
	struct book
	{
		int pages;
		int no;
	};
	struct book b[100];
	int i,n,j;
	scanf("%d", &n);
	for(i=0;i<n;i++)
	{
		printf("Enter pages");
		scanf("%d", b[i].pages);
		printf("Enter Book Number");
		scanf("%d", b[i].no);
	}
	for(j=0;j<n;j++)
	{
		printf("Pages are %d", b[j].pages);
		printf("Number is %d", b[j].no);
	}
	getch();
	return 0;
}

[donbock]

In general, your programs should protect themselves from somebody entering sizes (no,n) that are bigger than your preallocated arrays; or from somebody entering a string via gets that overflows your preallocated string variables.

Presumably you wouldn't have used test cases that overflow these limits. The errors you're getting sound pretty ominous. I suggest you contact your compiler's technical support folks to find out what these error messages mean.

[rusty uts]

Well I am using Turbo C++ 4.5. However I havent used cases where sizes of variables are greater than their preallocated arrays. I am at a total confusion, is this the operating system's fault? If u have that compiler can u just run this program and see whether it works or not, as I am begining to think that something is wrong with my Windows XP and not the code(Dont know why I feel that way probably as my machine hasnt been formatted for like 3 yrs)

[rusty uts]

The first program is to sort a number of arrays of structures on the basis of the marks. The guy with lowest marks gets their names and marks printed first, then the one with higher marks and so on!! The second is just a simple program to input data in a structure and reprint them on the screen, BTW if u feel there is something wrong with the code then please do let me know!! Thanks in advance!!

[puneetsardana88]

For the second question you are forgetting to add & while inputting

            printf("Enter pages");
            scanf("%d", &b[i].pages);
            printf("Enter Book Number");
            scanf("%d", &b[i].no);

This works fine....

[rusty uts]

@Puneet Thanks man, it worked!! I really was being stupid overlooking the obvious mistake!!

[rusty uts]

However the first one still doesnt respond, even when the "&" case is fixed. It causes problems in toolhelp.dll or something, anybody knows why this is happening??

[puneetsardana88]

    #include<stdio.h>
    #include<conio.h>
    #include<string.h>
    main()
    {
        struct boy
        {
            char name[100];
            int marks;
        };
        struct boy a[100];
        int no,i,l,m,k,t;
        char nam[100];
        printf("Enter no of students");
        scanf("%d", &no);
        for(i=0;i<no;i++)
        {
            printf("Enter Name  ");
            scanf("%s",(a[i].name));
            printf("Enter Marks  ");
            scanf("%d", &a[i].marks);
        }
        for(l=1;i<=no-1;l++)
        {
            for(m=0;m<no-l;m++)
            {
                if(a[m].marks>a[m+1].marks)
                {
                    strcpy(nam,a[m].name);
                    strcpy(a[m].name,a[m+1].name);
                    strcpy(a[m+1].name,nam);
                    t=a[m].marks;
                    a[m].marks=a[m+1].marks;
                    a[m+1].marks=t;
                }
            }
        }
        for(k=0;k<no;k++)
        {
            puts(a[k].name);
            printf("%d", a[k].marks);
        }
        getch();
        return 0;
    }

Works fine...Check out the changes made

[rusty uts]

@Puneet Thanks for ur effort, but it doesnt seem to run. This toolhelp.dll stack fault is still happening. U ran it in ur PC right? If it did run then my Operating System is probably at fault. BTW, the only differences are the "&", and the scanf("%s" instead of the gets() part right? The rest seems to be the same. Anyway if it worked on ur PC, can u tell me why we cant use gets() here? I mean scanf("%s" and gets() would do the same thing right? Only difference that gets() will automatically put the '\0' character at the end while scanf will not, Right?

[puneetsardana88]

@ rusty uts

The code that I posted works fine for me. I am running in code block mingw compiler. Please check

[rusty uts]

@Puneet Thanks man, turns out that my turbo C++ 4.5 was corrupted or something, started using code::Blocks, works great, And its better as well, so thanks again!!