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) {
    strcpy(buffer, user_input);
    // ...
    free(buffer);
}
```

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

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

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

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

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

// After: Fixed CWE-787 vulnerability
char *buffer = new char[userInput.length() + 1];
if (buffer != NULL) {
    strcpy(buffer, userInput);
    // ...
    delete[] buffer;
}
```

**5. C# Code Completion**
```csharp
// Before: CWE-787 vulnerability
// byte[] buffer = new byte[10];
// Array.Copy(userInput, buffer, userInput.Length);

// After: Fixed CWE-787 vulnerability
byte[] buffer = new byte[userInput.Length];
Array.Copy(userInput, buffer, userInput.Length);
```

In each example, the fix involves allocating a buffer that is large enough to hold the input data, and then copying the input data into the buffer using a safe function. This prevents the out-of-bounds write vulnerability.