Comment 23 for bug 1109327

Hi,

Rich Felker wrote:

> --- vfprintf.c.orig
> +++ vfprintf.c
> @@ -1168,42 +1168,7 @@
> else if (!is_long && spec != L_('S')) \
> { \
> if (prec != -1) \
> - { \
> - /* Search for the end of the string, but don't search past \
> - the length (in bytes) specified by the precision. Also \
> - don't use incomplete characters. */ \
> - if (_NL_CURRENT_WORD (LC_CTYPE, _NL_CTYPE_MB_CUR_MAX) == 1) \
> len = __strnlen (string, prec); \
> - else \
> - { \
> - /* In case we have a multibyte character set the \
> - situation is more complicated. We must not copy \
> - bytes at the end which form an incomplete character. */\
[...]
> - len = str2 - string - (ps.__count & 7); \
> - } \
> - } \
> else \
> len = strlen (string); \
> } \
> This patch fixes the bug. As I suspected, it's all -'s, no +'s.

Thanks. wprintf(3) tells me:

 s
  If no l modifier is present: The const char * argument
  is expected to be a pointer to an array of character
  type (pointer to a string) containing a multibyte character
  sequence beginning in the initial shift state.
  Characters from the array are converted to wide
  characters (each by a call to the mbrtowc(3) function
  with a conversion state starting in the initial state
  before the first byte). The resulting wide characters
  are written up to (but not including) the terminating
  null wide character.
[etc]

C99 says that in this case "the argument shall be a pointer to the
initial element of a character array containing a multibyte character
sequence beginning in the initial shift state". POSIX uses similar
wording. C99 describes an error condition:

 The fwprintf function returns the number of wide characters
 transmitted, or a negative value if an output or encoding
 error occurred.

POSIX does not document what value errno should have in this case, but
presumably EILSEQ is typical, for consistency with mbrtowc.

Luckily these considerations only matter in the defined(COMPILE_WPRINTF)
case. Your patch only modifies the !defined(COMPILE_WPRINTF) code.
So for what it's worth:

Reviewed-by: Jonathan Nieder <email address hidden>