Is it possible to copy a string using C's strcpy
without first assigning memory to a char *character_array
?
Basically, is something like this possible:
strcpy(char *my_string, another_string);
where my_string
becomes an initialised string with the same length and content as another_string
.
strcpy
never allocates memory. The destination must be a pointer to enough, writable, validly-allocated memory, and you are responsible for making sure that the destination memory is validly allocated, long enough, and writable.
So these are all okay:
char *another_string = "hello";
char my_string_1[20];
strcpy(my_string_1, another_string); /* valid (plenty of space) */
char my_string_2[6];
strcpy(my_string_2, another_string); /* valid (just enough space) */
char my_string_3[] = "world";
strcpy(my_string_2, another_string); /* valid (just enough space) */
char buf[6];
char *my_string_4 = buf;
strcpy(my_string_4, another_string); /* valid (via intermediate pointer) */
char *my_string_5 = malloc(6);
strcpy(my_string_5, another_string); /* valid (assuming malloc succeeds) */
char *my_string_6 = malloc(strlen(another_string) + 1);
strcpy(my_string_6, another_string); /* valid (assuming malloc succeeds) */
But these are not valid:
char my_string_7[5];
strcpy(my_string_7, another_string); /* INVALID (not enough space) */
char *my_string_8 = "world";
strcpy(my_string_8, another_string); /* INVALID (destination not writable) */
char *my_string_9;
strcpy(my_string_9, another_string); /* INVALID (destination not allocated) */
char *my_string_10 = malloc(20);
free(my_string_10);
strcpy(my_string_10, another_string); /* INVALID (no longer allocated) */
char *exceptionally_bad_allocator()
{
char local_buffer[20];
return local_buffer;
}
char *my_string_11 = exceptionally_bad_allocator();
strcpy(my_string_11, another_string); /* INVALID (not validly allocated) */