To generate the patch for the given code slice, we need to follow a systematic approach to identify the root cause of the vulnerability and then apply an appropriate fix. Here are the reasoning steps:

### Step 1: Root Cause Analysis

1. **Understanding the Code:**
   - The function `eel_g_settings_add_auto_int` takes three parameters: a `GSettings` object, a key, and a pointer to an integer storage.
   - It retrieves an integer value from the settings using the provided key and stores it in the location pointed to by `storage`.
   - It then constructs a signal string by concatenating `"changed::"` with the key.
   - Finally, it connects the signal to the `update_auto_int` callback function, passing the storage pointer as user data.

2. **Identifying Memory Allocation:**
   - The function `g_strconcat` is used to concatenate strings and returns a newly allocated string. This memory is dynamically allocated and needs to be freed after use to avoid memory leaks.

3. **Potential Vulnerability:**
   - The dynamically allocated memory for the `signal` string is not freed after it is used in the `g_signal_connect` function.
   - This results in a memory leak, as the allocated memory is not released, leading to a CWE-401 (Memory Leak) vulnerability.

### Step 2: Fixing Strategy

1. **Memory Management:**
   - To fix the memory leak, we need to ensure that the dynamically allocated memory for the `signal` string is properly freed after it is no longer needed.

2. **Applying the Fix:**
   - After the call to `g_signal_connect`, we should free the memory allocated for the `signal` string using the `g_free` function.

### Conclusion

The patch should include a call to `g_free(signal)` after the `g_signal_connect` function to release the allocated memory and prevent the memory leak. The corrected code is as follows:

```c
<     g_signal_connect(settings, signal, G_CALLBACK(update_auto_int), storage);
< }---
>     g_signal_connect(settings, signal, G_CALLBACK(update_auto_int), storage);
>     g_free(signal);
> }
```

### Summary of Reasoning Steps:

1. **Identify the Root Cause:**
   - Recognize that `g_strconcat` allocates memory that needs to be freed.
   - Determine that the memory allocated for `signal` is not freed, leading to a memory leak.

2. **Fix the Vulnerability:**
   - Add a call to `g_free(signal)` after the `g_signal_connect` function to release the allocated memory.

By following these steps, we ensure that the dynamically allocated memory is properly managed, thus preventing the memory leak and addressing the CWE-401 vulnerability.