[Cython] char* to string conversion

[Stefan Behnel]

Jack Stahl wrote:
> Quick question.  If I want to return a char * from Cython to Python as a
> string, should I be freeing the original char * or not?  In other words,
> when Cython does the implicit conversion from char * ---> string, does it
> create a Python object and strcpy the char * into its data, or does it copy
> the pointer?

It creates a copy that is owned by the str/bytes object.


> Here's some code to make this clearer:
> 
> cdef class MyStringHolder:
> 
>   cdef char *my_str
> 
>   ...
> 
>   cpdef add_to_set(object set):
>     // Is this necessary or is this a memory leak?
>     cdef char * str_cpy = <char*>malloc(strlen(my_str) + 1)
>     strcpy(str_cpy, my_str)
> 
>     // Should this just be set.add(my_str)?
>     set.add(str_cpy)

Yes, passing my_str should be enough (unless what you want is actually a
unicode string, in which case you need to decode it).

Stefan