Re: [Qemu-devel] error compiling hw/sh7750.c

[Andreas Schwab]

Carlo Marcelo Arenas Belon <address@hidden> writes:

> and run a test, the problem is in /usr/include/iso/stdio_iso.h that defined
> NULL as an int and not a pointer as shown by :

NULL is not a pointer, it is a null pointer constant, and 0 is a valid
null pointer constant.

> contradicting (at least in spirit) the C99 (ISO/IEC 9899:TCS) standard that
> says :
>
>   "A pointer to void shall have the same representation and alignment 
>    requirements as a pointer to a character type"

A null pointer constant is not a pointer.  It can be convert to a
pointer, but that happens only in the right context (through explicit or
implicit conversions).

> and therefore makes sizeof(*NULL) == 1 solving the problem to compile as it is
> done if applying the following patch :
>
> Carlo
>
> ---
> --- qemu/hw/sh7750.c  Sun Oct  7 09:31:11 2007
> +++ qemu/hw/sh7750.c  Sun Nov 11 16:13:13 2007
> @@ -29,6 +29,9 @@
>  #include "sh7750_regnames.h"
>  #include "sh_intc.h"
>  
> +#undef NULL
> +#define NULL ((void *)0)

This does not make it better, since sizeof(void) is still not allowed in
C.

Andreas.

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Andreas Schwab, SuSE Labs, address@hidden
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