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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