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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: u8"" c11 c23
Date: Mon, 20 Oct 2025 15:19:11 -0700
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Thiago Adams <thiago.adams@gmail.com> writes:
> speaking on signed x unsigned,
>
> u8"a"  in C11 had the type char [N]. Normally char is signed

I would have said "commonly" rather than "normally".  Not an
important point.

> in C23 it is unsigned char8_t  [N].
>
> when converting code from c11 to c23 we have a error here
> const char* s = u8""
>
>
> I generally "cast char* " to "unsigned char*" when handling something
> with utf8. I am not u8"" , I use just " " with utf8 encoded source
> code and I just assume const char* is utf8.

That raises another issue.

The <uchar.h> header was introduced in C99.  In C99, C11, and C17,
that header defines char16_t and char32_t.  C23 introduces char8_t.

There doesn't seem to be any way, other than checking the value of
__STDC_VERSION__ to determine whether char8_t is defined or not.  There
are not *_MIN or *_MAX macros for these types, either in <uchar.h> or in
<limits.h>.  A test program I just wrote would have been a little
simpler if I could have used `#ifdef CHAR8_MAX`.

Here's the test program :

#include <stdio.h>
#include <uchar.h>

#define TYPEOF(x) \
    (_Generic(x, \
        char: "char", \
        signed char: "signed char", \
        unsigned char: "unsigned char", \
        short: "short", \
        unsigned short: "unsigned short", \
        int: "int", \
        unsigned int: "unsigned int", \
        long: "long", \
        unsigned long: "unsigned long", \
        long long: "long long", \
        unsigned long long: "unsigned long long"))

int main(void) {
    printf("__STDC_VERSION__ = %ldL\n", __STDC_VERSION__);
    printf("u8\"a\"[0] is of type %s\n",
           TYPEOF(u8"a"[0]));
#if __STDC_VERSION__ >= 202311L
    printf("char8_t is %s\n", TYPEOF((char8_t)0));
#endif
    printf("char16_t is %s\n", TYPEOF((char16_t)0));
    printf("char32_t is %s\n", TYPEOF((char32_t)0));
}

Its output with `gcc -std=c17` :

__STDC_VERSION__ = 201710L
u8"a"[0] is of type char
char16_t is unsigned short
char32_t is unsigned int

Its output with `gcc -std=c23` :

__STDC_VERSION__ = 202311L
u8"a"[0] is of type unsigned char
char8_t is unsigned char
char16_t is unsigned short
char32_t is unsigned int

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */