A segmentation fault (seg fault) happens when the program tries to access a memory location outside the boundaries that were allocated. This can be caused by various reasons such as accessing an uninitialized pointer or free memory, stack overflow, or writing to a read-only memory location.

To debug this issue, you can try to use a debugger to track down the location where the program crashes. One common tool is gdb (GNU Debugger), which is available on most Unix-based systems. You can run your code in a debugger by compiling it with the -g flag (to include debugging symbols) and then running:

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$ gdb your_program
(gdb) run

When the program crashes, gdb will stop and you can use commands like backtrace to see where the crash happened, and print to inspect variable values.

Here's an example of how to use gdb to debug a C program:

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#include <stdio.h>

int main() {
    int arr[3] = {1, 2, 3};
    printf("%d\n", arr[4]);   // Accessing out-of-bounds memory
    return 0;
}

Compile with debugging symbols:

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$ gcc -g segfault.c -o segfault

Run in gdb:

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$ gdb segfault
(gdb) run

gdb will show a message similar to this:

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Program received signal SIGSEGV, Segmentation fault.
0x00005555555546c3 in main ()

This means that the program crashed in the main function. You can use backtrace to see the call stack:

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(gdb) backtrace
#0  0x00005555555546c3 in main ()

And you can use print to inspect the variable values:

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(gdb) print arr
$1 = {1, 2, 3}

As you can see, accessing arr[4] caused the seg fault, because arr only has 3 elements.