Bug on sizeof(void) == 1, must be undefined or negative, == -100000.

[jc-nospam]

Please, to run this script of 5 lines:

#!/bin/sh
cat > bug_void.c <

Re: Bug on sizeof(void) == 1, must be undefined or negative, == -100000.

[jc-nospam]

On Jun 17, 2005, at 17:05:37, [EMAIL PROTECTED] wrote:

> This is invalid code and a GNU extension to take the sizeof(void).  The 
> reason
> why GCC defines it as 1 is because you can do the following:
> void *a;
> a++;
>
> If you want to error out on GNU extensions, use -pedantic-errors.
>
> Thanks,
> Andrew Pinski

To imagine the worst situation:

char *x = (char *)0xBAD0DAD0;
x++; // -> x = 0xBAD0DAD1 (adding +1)
int *y = x;  // -> y = 0xBAD0DAD1
y++; // -> y = 0xBAD0DAD5 (adding +4, sizeof(int)==4 )
void *z = y; // -> z = 0xBAD0DAD5
z++; // adding +0? adding +1? adding +4? abort this error?

Sincerely yours, J.C.

Re: Bug on sizeof(void) == 1, must be undefined or negative, == -100000.

[jc-nospam]

On Jun 17, 2005, at 17:31:34, [EMAIL PROTECTED] wrote:

> Since this is a GNU extension, GCC defines as adding 1.  See the  
> documentation
> where this is documented.
> http://gcc.gnu.org/onlinedocs/gcc-4.0.0/gcc/Pointer-Arith.html#Pointer- 
> Arith
>
>
>   In GNU C, addition and subtraction operations are supported on  
> pointers to void and on pointers to functions. This is done by treating  
> the size of a void or of a function as 1.
>
>   A consequence of this is that sizeof is also allowed on void and on  
> function types, and returns 1.
>
> The option -Wpointer-arith requests a warning if these extensions are  
> used.
>
> -- Pinski

Conclusion: the GNU's law is:

 "void IS A byte"
(1 void == 1 byte)

-- J.C. --