optimization/4130: gcc 3.0 -O2 and printf optimization

[Richard Kettlewell]

rth@gcc.gnu.org writes:
> Synopsis: gcc 3.0 -O2 and printf optimization
> 
> State-Changed-From-To: open->closed
> State-Changed-By: rth
> State-Changed-When: Wed Apr  3 00:20:49 2002
> State-Changed-Why:
>     According to Uli Drepper, whom I consider an authority in this area:
>     
>        The handling of byte sequences which are not valid in the current locale
>        is unspecified.  Either result is valid.  There is the different result
>        but people writing incorrect code should not get into to way of
>        optimizing code.  And there always is the opportunity to compile with -O0.
>     
>     Although -fno-builtin-printf is certainly more palletable
>     than -O0.
> 
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=4130

My copy of the draft standard says:

    An encoding error occurs if the character sequence presented to
    the underlying mbrtowc function does not form a valid
    (generalized) multibyte character, or if the code value passed to
    the underlying wcrtomb does not correspond to a valid
    (generalized) multibyte character. The wide-character input/output
    functions and the byte input/output functions store the value of
    the macro EILSEQ in errno if and only if an encoding error occurs.

And:

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

Granted this may have changed between the draft and the standard, but
it looks quite adequately specified to me.

ttfn/rjk