Here are five possible code completions for fixing a CWE-787 vulnerability, which is related to Out-of-bounds Write. I'll provide examples in different programming languages.

**1. C Code Completion**
```c
// Before: CWE-787 vulnerability
// char *buffer = malloc(10);
// strcpy(buffer, user_input);

// After: Fixed CWE-787 vulnerability
char *buffer = malloc(strlen(user_input) + 1);
if (buffer == NULL) {
    // Handle memory allocation error
}
strcpy(buffer, user_input);
```

**2. Java Code Completion**
```java
// Before: CWE-787 vulnerability
// byte[] buffer = new byte[10];
// System.arraycopy(user_input.getBytes(), 0, buffer, 0, user_input.length());

// After: Fixed CWE-787 vulnerability
byte[] buffer = new byte[user_input.length()];
System.arraycopy(user_input.getBytes(), 0, buffer, 0, user_input.length());
```

**3. Python Code Completion**
```python
# Before: CWE-787 vulnerability
# buffer = bytearray(10)
# buffer[:len(user_input)] = user_input.encode()

# After: Fixed CWE-787 vulnerability
buffer = bytearray(len(user_input))
buffer[:len(user_input)] = user_input.encode()
```

**4. C++ Code Completion**
```cpp
// Before: CWE-787 vulnerability
// char *buffer = new char[10];
// strcpy(buffer, user_input.c_str());

// After: Fixed CWE-787 vulnerability
char *buffer = new char[user_input.length() + 1];
if (buffer == NULL) {
    // Handle memory allocation error
}
strcpy(buffer, user_input.c_str());
```

**5. PHP Code Completion**
```php
// Before: CWE-787 vulnerability
// $buffer = str_repeat(' ', 10);
// $buffer = substr_replace($buffer, $user_input, 0, strlen($user_input));

// After: Fixed CWE-787 vulnerability
$buffer = str_repeat(' ', strlen($user_input));
$buffer = substr_replace($buffer, $user_input, 0, strlen($user_input));
```

In each example, the fix involves allocating a buffer that is large enough to hold the user input, preventing a potential out-of-bounds write.