This lesson's interactive features are locked, please to keep using them

String

Now we're going to do our first object that has something... additional allocated. When we allocate memory for a "snek object", that reserves memory for the object itself. Small data types like integers and floats are stored directly in the object, so there's no need for additional memory allocation.

Strings, however, are a different story. Strings in C are just arrays of characters, and because they can be any length, we need to dynamically allocate memory for the string data separately from the object itself.

char *my_string = "hello world";

In the example above, my_string is a pointer to a character array. The character array contains:

h
e
l
l
o

w
o
r
l
d
\0

The extra spot at the end with the \0 is the null terminator. It's how C knows where the string ends.

Assignment

In snekobject.h:
1. Add a new enum value to the snek_object_kind_t enum called STRING.
2. Add a new string (char *) field to snek_object_data_t called v_string
3. Declare the new_snek_string function.
In snekobject.c, complete the new_snek_string function. It should:
1. Allocate memory for a new pointer to a snek_object_t.
2. If the allocation fails, return NULL.
3. Calculate the length (in bytes using strlen) of the string passed in.
4. Allocate memory in a char * field equal to the length of the string plus one (for the null terminator).
5. If the allocation fails, free the memory allocated for the snek object, then return NULL.
6. Copy the data from the input value into the new string field you just allocated using strcpy.
7. Set the kind field to the appropriate enum.
8. Store the newly allocated string in the object.
9. Return the pointer to the new snek object.