What is the difference between these two pointer declarations?

Question

Are these declarations different or do the produce the same result?

char * const *argv;

and

const char **argv;

Is there a difference or are both pointer to a pointer?

The background is that I was writing a C commandline shell and used this struct for a command:

struct command
{
    char * const *argv;
};

The above struct was used to call exec. Now when I looked at another question then the struct was different:

In that question the struct to achieve the same is different.

[This entry in the C-faq](http://c-faq.com/ansi/constptrconst.html) may help (plus a bit of extrapolation to your case). — , Apr 11 '16 at 07:13
@Shripada There are no arrays in the code shown. Only pointers. — juanchopanza, Apr 11 '16 at 07:14
possible [duplicate](http://stackoverflow.com/questions/890535/what-is-the-difference-between-char-const-and-const-char) — jdarthenay, Apr 11 '16 at 07:18
I'm curious about one thing. Did you really meant this ==>> `const char **argv;` or you meant this ==>> `const char *argv;`? — Michi, Apr 11 '16 at 09:59
@Michi I'm going to try and add some background to the question. — Niklas Rosencrantz, Apr 11 '16 at 15:35

nalzok · Accepted Answer · 2016-04-11T07:35:35.893

7

They are totally different:

char *const *argv; declares "a pointer to const pointer to char";

const char **argv; declares "a pointer to pointer to const char";

Also, char **const argv; declares "a const pointer to pointer to char".

To understand these declarations, try reading them "inside out": http://c-faq.com/decl/cdecl1.html

edited Apr 11 '16 at 07:35

answered Apr 11 '16 at 07:24

nalzok

1

It could be that the Answer is based on a mistyping. I think he meant `const char *argv;`. One less star :) – Michi Apr 11 '16 at 10:02

1 Answers1