Re: full_read depends on incoming errno

[Paul Eggert]

On 02/19/13 13:15, Eli Zaretskii wrote:
>     if (full_read (fd, cookie, sizeof cookie) != sizeof cookie
>       || full_read (fd, SCM_BYTEVECTOR_CONTENTS (bv),
>                     SCM_BYTEVECTOR_LENGTH (bv)) != SCM_BYTEVECTOR_LENGTH (bv))
>       {
>         int errno_save = errno;
>         (void) close (fd);
>         errno = errno_save;
>         SCM_SYSERROR;
>       }
> 
...
> If the file is too short for these two reads, then errno will have
> some random value (because full_read "succeeded" as far as that
> function is concerned), and the error message in SCM_SYSERROR will
> display something utterly unrelated

Yes, full_read should return a short value and set errno to 0,
so errno_save should be zero.  If SCM_SYSERROR displays
a seemingly-unrelated diagnostic like "Error 0", that would
explain the problem.

> I think it's a Guile
> problem, since from gnulib POV, nothing went wrong in that call.

Yes, that sounds right.