Strange core dump

[jcarouth]

I have a program that compiled on my i386 running suse linux with

gcc -Wall student.c and runs perfectly.

When trying to compile and run the same program on a unix machine, I am recieving a segmentation fault at the following code

    fgets(line, sizeof(line), fp);
    if(!sscanf(line, "%d", &numRecords)) {
        printf("File not in the correct format.\n");
        exit(1);
    }

If i remove the unary & operator, there is no segmentation fault, but of couse numRecords is garbage and unusable. I don't understand how this works on one system and not another. Any suggestions?

entire source attached.

[jcarouth]

INPUT FILE
---------------------------

5
Jeffrey Carouth 371625342 MATH152 4 3 PHYS218 4 4 ENGR111 2 4 HIST105 3 3 CPSC206 4 4
Bob Dillan 873193526 MATH151 4 3 PHYS218 4 4 ENGR111 2 3 KINE199 1 4 POLS206 3 4
Matthew Bennett 943721745 MATH150 4 2 ENGR111 2 2 PHYS218 4 1 HIST105 3 3 LAND111 3 1
Jasen Petersen 624392761 MATH111 3 4 BUSI112 4 3 MGMT209 4 4 HIST109 3 3 MKTG209 4 4
Jordan Brown 926873321 ENGL432 3 4 ENGR482 3 4 CPSC469 3 3 MKTG422 4 4 HIST322 3 4

[nkhambal]

You need to check for NULL with fgets() which is returned at EOF.

if (fgets(line, sizeof(line), fp) != NULL)
{
    if(!sscanf(line, "%d", &numRecords)) {
	printf("File not in the correct format.\n");
	exit(1);
    }
}

[jcarouth]

Doing a

fgets(line, sizeof(line), fp);
puts(line);
//sscanf code

I get an output string of
5
as expected.

[ZuK]

The original code doesn't like empty lines in the input-file.
Kurt

[jcarouth]

That was the idea.....

There are no empty lines in the input file.

[ZuK]

If I run your original code with an inputfile without empty lines it runs fine.
If I put an empty line as first line into the file it seg-faults.
Kurt

[nkhambal]

I have modified the original code. I could complie it on Windows as well as Unix platform.

[jcarouth]

Thank you nkhambal. It compiled and ran on the machine in question. Can I ask you to explain the changes you made?

[nkhambal]

Here is the diff between your code and the one that I modified.

studentold.c is your code and student.c is mine. "<" indicates code lines removed/changed from your code and ">" indicates the code lines added by me.

Thanks,