Segmentation fault (core dumped)

Your program tried to access memory it doesn’t own. The OS killed it to prevent damage. This is almost always a pointer or array issue.

Fix 1: Null Pointer Dereference

// ❌ Pointer is NULL
int *ptr = NULL;
*ptr = 42;  // 💥 Segfault

// ✅ Check before dereferencing
if (ptr != NULL) {
    *ptr = 42;
}

Fix 2: Array Out of Bounds

// ❌ Accessing beyond array size
int arr[5];
arr[10] = 42;  // 💥 Segfault

// ✅ Stay within bounds
for (int i = 0; i < 5; i++) {
    arr[i] = i;
}

Fix 3: Using Freed Memory

// ❌ Use after free
int *ptr = malloc(sizeof(int));
free(ptr);
*ptr = 42;  // 💥 Segfault

// ✅ Set to NULL after free
free(ptr);
ptr = NULL;

Fix 4: Stack Overflow from Deep Recursion

// ❌ No base case
void recurse() {
    recurse();  // 💥 Eventually segfaults
}

// ✅ Add a base case
void recurse(int n) {
    if (n <= 0) return;
    recurse(n - 1);
}

Fix 5: Writing to Read-Only Memory

// ❌ String literals are read-only
char *str = "hello";
str[0] = 'H';  // 💥 Segfault

// ✅ Use a char array
char str[] = "hello";
str[0] = 'H';  // Works

Debugging

# Compile with debug symbols
gcc -g -o myapp myapp.c

# Run with Valgrind (finds memory errors)
valgrind ./myapp

# Run with AddressSanitizer
gcc -fsanitize=address -g -o myapp myapp.c
./myapp

# Get a backtrace from core dump
gdb ./myapp core
(gdb) bt

Related resources

• Rust borrow checker — how to fix it
• Node.js heap out of memory fix Related: Kubernetes OOMKilled — How to Fix It