#include <stdio.h>
#include <locale.h>
#include <string.h>
#include <wchar.h>
int main(void)
{
setlocale(LC_ALL, "en_US.utf8");
mbstate_t state;
memset(&state, 0, sizeof state);
char in[] = u8"z\u00df\u6c34\U0001F34C"; size_t in_sz = sizeof in / sizeof *in;
printf("Processing %zu UTF-8 code units: [ ", in_sz);
for(size_t n = 0; n < in_sz; ++n) printf("%#x ", (unsigned char)in[n]);
puts("]");
wchar_t out[in_sz];
char *p_in = in, *end = in + in_sz;
wchar_t *p_out = out;
int rc;
while((rc = mbrtowc(p_out, p_in, end - p_in, &state)) > 0)
{
p_in += rc;
p_out += 1;
}
size_t out_sz = p_out - out + 1;
printf("into %zu wchar_t units: [ ", out_sz);
for(size_t x = 0; x < out_sz; ++x) printf("%#x ", out[x]);
puts("]");
}