Is this a bug?

[Martin Kahlert <martin.kahlert@infineon.com>]

Hi!
I have code similar to this:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void f(const char **x)
{
 while(*x)
    {
     puts(*x);
     x++;
    }
}

int main(int argc,char *argv[])
{
 char **buffer;

 buffer = calloc(3, sizeof(char*));

 buffer[0] = strdup("Hello");
 buffer[1] = strdup("World");

 f(buffer);

 return 0;
}

gcc -Wall -o prog prog.c gives:

t.c: In function `main':
t.c:23: warning: passing arg 1 of `f' from incompatible pointer type
(the warning comes from the missing const)
Is this a bug?

At least it is an inconsistency:

f(const char *buffer)
{
 puts(buffer);
}

int main()
{
 char b[] = "Hello World";
 f(b);
 return 0;
}

works without any warning!

Thanks for any clarification,
Martin.


-- 
The early bird gets the worm. If you want something else for       
breakfast, get up later.
>From jsm28@cam.ac.uk Wed Dec 06 03:55:00 2000
From: "Joseph S. Myers" <jsm28@cam.ac.uk>
To: Martin Kahlert <martin.kahlert@infineon.com>
Cc: <gcc-bugs@gcc.gnu.org>
Subject: Re: Is this a bug?
Date: Wed, 06 Dec 2000 03:55:00 -0000
Message-id: <Pine.LNX.4.30.0012061150200.31115-100000@kern.srcf.societies.cam.ac.uk>
References: <20001206124239.A20108@keksy.muc.infineon.com>
X-SW-Source: 2000-12/msg00131.html
Content-length: 531

On Wed, 6 Dec 2000, Martin Kahlert wrote:

> t.c: In function `main':
> t.c:23: warning: passing arg 1 of `f' from incompatible pointer type
> (the warning comes from the missing const)
> Is this a bug?

No; you can pass a "char **" to a function expecting a "char **" or a
"char *const *", but not to one expecting a "const char **" or a "const
char *const *".  It's only at the first level of indirection that you can
have different type qualifiers in the expected type and the type passed.

-- 
Joseph S. Myers
jsm28@cam.ac.uk