From your description, it seems like the memory leak is happening in the C code you are using with your Python bindings. I’ll focus on the C code to identify potential issues.

1. In getline_stdin_mem_alloc() Function:
• The function allocates memory and returns a pointer to this memory. However, if getline() fails (returns -1), the memory is freed. This is correct.
• After freeing, it correctly sets buffer to NULL within the function’s local context. But this doesn’t affect the pointer in the calling function (prompt_input_getline). This is usually not a problem, as the calling function checks the returned pointer.
2. In prompt_input_getline() Function:
• The function receives the buffer from getline_stdin_mem_alloc() and then returns it. The responsibility to free this memory is now on the caller of prompt_input_getline().
3. In the clear_ptr() Function:
• This function frees the memory and sets the local copy of the pointer to NULL. However, this does not nullify the pointer in the caller’s context in C. This is a common misconception in C pointer handling. Setting a pointer to NULL in a function does not affect the pointer in the calling function unless you pass a pointer to the pointer.
4. In Python Code:
• You correctly call clear_ptr to free the memory. However, the y in your Python code still holds the address of the now-freed memory. This is not directly causing a memory leak but could lead to undefined behavior if you try to use y after this.

To address the memory leak issue, let’s look at a few points:

• Ensure that every malloc or getline (which internally does allocation) is paired with exactly one free.
• The memory leak might not be in the functions you’ve shown. It could be in how these functions are used, or in other parts of your program.
• Double-check that there are no other paths in your C code where memory is allocated but not freed.
• Consider using a pointer-to-pointer (char **) in clear_ptr if you want to set the original pointer to NULL in the caller’s context.

Since you’re interfacing with Python, it’s crucial to be meticulous with memory management. The garbage collector in Python will not manage memory allocated in C.

If you’re still having issues, it might be helpful to see more of the code, especially how these functions are being used in different contexts, to provide more targeted advice.