With
using gcc, new users generally gets a segmentation fault while doing
operations with pointers in C. As gcc is the most robust
compiler of C, it doesn't allow to do anything wrong with memory
references. Your TurboC++ compiler may allow invalid memory
references in many cases but gcc may not. But, don't be scared of it.
By using one of the best debuggers 'gdb' will find the line where
core dump- segmentation fault occurs.
There
are six reasons for occurrences of segmentation fault in C program.
Out of all, generation of SIGSEGV is most frequent event which leads
segmentation fault. Consider following example:
#include<stdio.h>
int
main()
{
int
x,*y,*z;
x=10;
*y=12;
*z=x+*y;
printf(”Addition
is %d”,*z);
return(0);
}
This
program will work fine in TurboC++ compiler but gcc will
produce segmentation fault. As, it is a run time error the line where
return fault has occurred, won't be displayed. So, what to do..?
Let
see find it. First compile the program as,
gcc
myprogram.c
-g
The
program will be compiled successfully and it will generate a.out
file which is executable. We may use -o option also to give another
name to output file. The -g option here gives ability to output file
to get debugged. Now, the debugger will be enabled for output file
a.out . Use gdb (GNU debugger) to debug program.
gdb
a.out
This
will start debugging and gdb> prompt will be shown. Use 'break'
instruction to insert breakpoint in the program. Such as,
gdb>
break 1
It
will insert breakpoint at line no.1 in the program. Now, run the
program by 'run' command.
gdb>
run
This
will execute your program till first breakpoint then after, we may
step through our program by 'next' command. The 'next' command will
execute the program line by line.
Wherever
you find the segmentation fault, the program will stop on that line
it will also show the line number. The above program will stop the
execution due to segmentation fault on line no.6. It is invalid
memory reference which is not allowed by gcc!
