svn commit: r313982 - in head/sys/dev: agp al_eth an arcmsr bce beri/virtio bhnd/cores/usb buslogic ce cm cp ctau cx de ed fatm fe firewire hptiop hptmv iicbus isp le md ncr netmap ofw patm pccard ...

[Piotr P. Stefaniak]

On 2017-02-22 00:46:31, Bruce Evans wrote:
>On Mon, 20 Feb 2017, Conrad Meyer wrote:
>> Maybe this is moot.  I don't believe any architecture FreeBSD actually
>> supports has non-zero bitpattern NULL, but something weird like CHERI
>> might.
>
>Compilers should do portability checks on it.  In fact, the convolutions
>in this file do little except define nullptr and __null to let compilers
>do more checking.  Only the C++ case even has them.  Compilers can do
>most checks using just the C90 definition of null pointer constants.

tcc(1) of the TenDRA project can set the null pointer representation to
0x55555555 via -f option of trans(1) (but only on x86):

$ cat test.c
#include <stdio.h>
int main(void)
{
	char *x = NULL;
	unsigned long int y = (unsigned long int)x;
	printf("%lx\n", y);
	return 0;
}

$ tcc ./test.c -o test
$ ./test
0
$ tcc -Wt,f ./test.c -o test
$ ./test
55555555

See http://www.tendra.org/trans.1/ for more details.
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