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Date: Mon, 27 Jul 2009 22:56:34 +0100
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Subject: bug in mbrtowc?
From: Andy Koppe <andy DOT koppe AT gmail DOT com>
To: Cygwin Tech List <cygwin AT cygwin DOT com>
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I've encountered what looks like a bug in mbrtowc's handling of UTF-8.
Here's an example:

#include <stdio.h>
#include <locale.h>
#include <stdlib.h>
#include <wchar.h>

int main(void) {
  wchar_t wc;
  size_t ret;
  mbstate_t s = { 0 };
  puts(setlocale(LC_CTYPE, "en_GB.UTF-8"));
  printf("%i\n", mbrtowc(&wc, "\xe2", 1, 0));
  printf("%i\n", mbrtowc(&wc, "\x94", 1, 0));
  printf("%i\n", mbrtowc(&wc, "\x84", 1, 0));
  printf("%x\n", wc);
  return 0;
}

The sequence E2 94 84 should translate to U+2514. Instead, the second
and third calls to mbrtowc report encoding errors. It does work
correctly if the three bytes are passed to mbrtowc() in one go:

  printf("%i\n", mbrtowc(&wc, "\xe2\x94\x84", 3, 0));

Andy

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