Hi,
While working on porting rust to arm64, I found something that seems a
bit odd for me, and I would like to have confirmation that it is
expected: the signess of char on arm64.
In order to test the sign of 'char' (unsigned or signed), I use the
following C program:
$ cat sign-of-char.c
#include <stdio.h>
int
main(int argc, char *argv[])
{
printf("char: %d\n", ((char) -1) < 0);
printf("signed char: %d\n", ((signed char) -1) < 0);
printf("unsigned char: %d\n", ((unsigned char) -1) < 0);
return 0;
}
on amd64, it reports:
amd64$ cc sign-of-char.c -o sign-of-char && ./sign-of-char
char: 1
signed char: 1
unsigned char: 0
so on amd64, 'char' is signed.
but on arm64, I get:
arm64$ cc sign-of-char.c -o sign-of-char && ./sign-of-char
char: 0
signed char: 1
unsigned char: 0
so on arm64 (aarch64), 'char' is unsigned.
Per se, it isn't a problem. And if I correctly understood, the standard
defines 3 distinct types ('char', 'signed char', and 'unsigned char')
and the signess of 'char' is implementation defined.
Also, several architecture-OS already has char unsigned, for example:
- aarch64-android
- powerpc-linux
- arm-linux
But I would like confirmation because for all BSD where I have the
information, I always have a signed char (aarch64-freebsd,
powerpc-netbsd, arm-netbsd, ...), except arm64 on OpenBSD.
Is it expected ?
--
Sebastien Marie
