Get size of pointer in C

c pointers sizeof
Matt picture Matt · Mar 18, 2012 · Viewed 62.7k times · Source

How do I get the size of a pointer in C using sizeof? I want to malloc some memory to store a pointer (not the value being pointed to).

Answer

Jonathan Leffler picture Jonathan Leffler · Mar 18, 2012

Given an arbitrary type (I've chosen char here, but that is for sake of concrete example):

char *p;

You can use either of these expressions:

sizeof(p)
sizeof(char *)

Leading to a malloc() call such as:

char **ppc = malloc(sizeof(char *));
char **ppc = malloc(sizeof(p));
char **ppc = malloc(sizeof(*ppc));

The last version has some benefits in that if the type of ppc changes, the expression still allocates the correct space.

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