It is impossible to provide specific code completions to fix a CWE-787 (Out-of-bounds Write) vulnerability without seeing the vulnerable code snippet. 

**CWE-787 (Out-of-bounds Write)** occurs when data is written past the end, or before the beginning, of a buffer allocated in memory. This can lead to data corruption, crashes, or even security vulnerabilities.

To fix a CWE-787 vulnerability, you need to **ensure that all write operations to buffers stay within their allocated bounds.**  Here's a general approach and five example scenarios:

**General Approach:**

1. **Identify the vulnerable code:** Find the code where data is being written to a buffer without proper bounds checking.
2. **Determine the buffer size:** Identify the allocated size of the buffer.
3. **Implement bounds checking:** Ensure that any write operation to the buffer respects its boundaries.

**Example Scenarios and Possible Completions:**

**1. Writing to an array with a loop:**

```c
// Vulnerable code:
int arr[10];
for (int i = 0; i <= 10; i++) { // Should be i < 10
    arr[i] = i; 
}

// Fixed code:
int arr[10];
for (int i = 0; i < 10; i++) { 
    arr[i] = i; 
}
```

**2. Copying data with `memcpy()` without size check:**

```c
// Vulnerable code:
char src[20] = "This is a source string";
char dest[10];
memcpy(dest, src, strlen(src)); 

// Fixed code:
char src[20] = "This is a source string";
char dest[10];
size_t bytesToCopy = strlen(src) + 1; // +1 for null terminator
if (bytesToCopy > sizeof(dest)) {
    bytesToCopy = sizeof(dest);
}
memcpy(dest, src, bytesToCopy);
```

**3. Using `strcpy()` without size limitation:**

```c
// Vulnerable code:
char buffer[16];
strcpy(buffer, "This string is too long!");

// Fixed code:
char buffer[16];
strncpy(buffer, "This string is too long!", sizeof(buffer) - 1);
buffer[sizeof(buffer) - 1] = '\0'; // Ensure null termination
```

**4. Accessing array elements based on user input:**

```c
// Vulnerable code:
int arr[5];
int index = get_user_input(); // Assume user inputs 7
arr[index] = 10;

// Fixed code:
int arr[5];
int index = get_user_input(); 
if (index >= 0 && index < 5) {
    arr[index] = 10;
} else {
    // Handle out-of-bounds index
}
```

**5. Using realloc() without checking the return value:**

```c
// Vulnerable code:
int* ptr = (int*)malloc(sizeof(int) * 5);
// ... some code ...
ptr = (int*)realloc(ptr, 10 * sizeof(int)); // What if realloc fails?
// ... accessing ptr assuming it was reallocated successfully ...

// Fixed code:
int* ptr = (int*)malloc(sizeof(int) * 5);
// ... some code ...
int* temp = (int*)realloc(ptr, 10 * sizeof(int)); 
if (temp != NULL) {
    ptr = temp;
} else {
    // Handle realloc failure
}
```

**Remember**: These are just examples. The specific fix for a CWE-787 vulnerability will depend on the context of the vulnerable code. Always carefully analyze your code and implement appropriate bounds checking to prevent these vulnerabilities. 
