Step 1:  code snippet provided does not directly show a CWE-476 (NULL Pointer Dereference) vulnerability in the line:
```
6 	char *sm_alternate = NULL, *error_strategy = NULL;
```
However, to reason about how a NULL pointer dereference vulnerability could occur, we need to consider the subsequent use of these pointers in the function `clone_submodule`. The vulnerability would typically manifest if these pointers are dereferenced without proper checks to ensure they are not NULL. Here’s a step-by-step analysis:

### Step 1: Initialization of Pointers
- The pointers `sm_alternate` and `error_strategy` are initialized to NULL.
- Initializing pointers to NULL is a common practice to ensure they are not pointing to arbitrary memory locations.

### Step 2: Potential Use of Pointers
- Since the actual usage of these pointers is not shown in the snippet, we must hypothesize based on common practices.
- These pointers might be intended to store addresses of strings or other data structures. If the function `clone_submodule` attempts to use these pointers (e.g., accessing data through them or passing them to other functions expecting valid addresses), it must first ensure they point to valid memory.

### Step 3: Hypothetical Vulnerable Behavior
- If `clone_submodule` or any function it calls tries to dereference `sm_alternate` or `error_strategy` without first checking if they are not NULL, it would lead to a NULL pointer dereference. For example:
  ```c
  if (strcmp(sm_alternate, "some_value") == 0) {
      // do something
  }
  ```
- In the above hypothetical code, if `sm_alternate` is still NULL when `strcmp` is called, it would cause a NULL pointer dereference because `strcmp` expects valid C-string pointers.

### Step 4: Ensuring Safety
- To prevent a NULL pointer dereference, the function should include checks before dereferencing these pointers:
  ```c
  if (sm_alternate != NULL && strcmp(sm_alternate, "some_value") == 0) {
      // do something
  }
  ```
- Additionally, the function might need to allocate memory or ensure that these pointers are assigned to valid addresses before any dereferencing occurs.

### Conclusion:
The vulnerability (CWE-476) would occur if there is an attempt to dereference `sm_alternate` or `error_strategy` without verifying that they have been assigned non-NULL values after their initialization. Proper checks should be implemented to ensure these pointers are valid before any operations that require dereferencing. The provided code snippet does not show the actual dereferencing, so the analysis assumes typical scenarios where such vulnerabilities might occur.
To address the potential CWE-476 vulnerability in the code snippet provided, where `sm_alternate` and `error_strategy` are initialized to NULL and might be used later in the function `clone_submodule`, here are five possible patches to ensure that these pointers are safely handled:

### Patch 1: Check before Dereferencing
Add checks before any dereferencing occurs to ensure the pointers are not NULL.

```diff
< // Hypothetical usage of sm_alternate
< if (strcmp(sm_alternate, "some_value") == 0) {
---
> // Safe usage of sm_alternate
> if (sm_alternate != NULL && strcmp(sm_alternate, "some_value") == 0) {
```

### Patch 2: Initialize with Default Values
Instead of initializing to NULL, initialize the pointers with default valid values if applicable.

```diff
< char *sm_alternate = NULL, *error_strategy = NULL;
---
> char *sm_alternate = "default_alternate", *error_strategy = "default_strategy";
```

### Patch 3: Dynamic Memory Allocation
Allocate memory for the pointers at the beginning and free it at the end of the function.

```diff
< char *sm_alternate = NULL, *error_strategy = NULL;
---
> char *sm_alternate = malloc(100); // Assuming 100 bytes needed
> char *error_strategy = malloc(100);
> if (!sm_alternate || !error_strategy) {
>     // Handle memory allocation failure
>     return -1;
> }
> // Use the pointers
> // Free the allocated memory at the end of the function
> free(sm_alternate);
> free(error_strategy);
```

### Patch 4: Parameter Validation
Validate the parameters at the beginning of the function to ensure they are not passed as NULL if they are supposed to be set before calling `clone_submodule`.

```diff
< int clone_submodule(const struct module_clone_data *clone_data) {
---
> int clone_submodule(const struct module_clone_data *clone_data) {
>     if (!clone_data || !clone_data->sm_alternate || !clone_data->error_strategy) {
>         // Handle invalid parameters
>         return -1;
>     }
```

### Patch 5: Error Handling and Early Return
Implement error handling and early return if the pointers remain NULL when they are required to be non-NULL.

```diff
< // Hypothetical point where sm_alternate is required to be non-NULL
< process_alternate(sm_alternate);
---
> // Check and handle if sm_alternate is NULL
> if (!sm_alternate) {
>     fprintf(stderr, "Error: sm_alternate is not set.\n");
>     return -1; // or handle the error as appropriate
> }
> process_alternate(sm_alternate);
```

Each of these patches addresses the potential for NULL pointer dereference in different ways, depending on the specific requirements and context of the function `clone_submodule`. These solutions range from adding safety checks, initializing with default values, managing dynamic memory, validating input parameters, to implementing robust error handling.