[Bug fortran/47694] [4.3/4.4/4.5/4.6 Regression] Fortran read from named pipe fails to read all available data

[jb at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47694

--- Comment #22 from Janne Blomqvist <jb at gcc dot gnu.org> 2011-02-24 15:08:00 UTC ---
(In reply to comment #21)
> (In reply to comment #20)
> > +      if (q == EOF)
> > 
> > Does this always work? We have in "static inline int fbuf_getc (gfc_unit * u)":
> >     return (unsigned char) u->fbuf->buf[u->fbuf->pos++];
> > and "q" is "int".
> > 
> > The issue I see is the following (quote from POSIX's fgetc(3p)):
> > "If the integer value returned by fgetc() is stored into a variable of type
> > char and then compared against the  integer constant EOF, the comparison may
> > never succeed, because sign-extension of a variable of type char on widening to
> > integer is implementation-defined."
> 
> You're missing the whole picture. The definition of fbuf_getc in fbuf.h is
> 
> static inline int
> fbuf_getc (gfc_unit * u)
> {
>   if (u->fbuf->pos < u->fbuf->act)
>     return (unsigned char) u->fbuf->buf[u->fbuf->pos++];
>   return fbuf_getc_refill (u);
> }
> 
> That is, the inlined fast path is for the case when there is data available in
> the buffer. If there isn't data, it falls back to fbuf_getc_refill, where if
> filling the buffer with more data fails EOF is returned, otherwise the next
> character cast to unsigned char. 

That is, there is never some kind of EOF character in the buffer, rather EOF is
a special error value which is returned when there is no more data available.