Re: STDIO - proposed fix for fread()

[Jonathan Larmour <jifl at eCosCentric dot com>]

Gary Thomas wrote:
> On Thu, 2003-03-06 at 12:41, Jonathan Larmour wrote:
>
> > Gary Thomas wrote:
> >
> > > The 'fread()' function works differently on eCos than it does on Linux. 
> > > Thusly, some programs which work fine on Linux fail on eCos.  The 
> > > problem is that fread() sets ferror() when it gets to the end of the 
> > > file (as well as setting feof()).  This patch fixes it, and also adds a 
> > > test for the condition.
> > >
> > > Does it make sense?  Shall I commit?
> >
> > Well those programs are using unspecified behaviour so strictly they are 
> > non-portable. Checking for ferror()  without a reported error is as porr 
> > practice as checking for errno without a reported error.
> >
> > But we may as well probably deal with this although I'm not particularly 
> > happy about adding a test for something that only non-portable programs 
> > use. But still it's the least worst option :-).
> >
> > If you could add a comment in the test saying as much that would be nice, 
> > i.e. standard doesn't require it, but we'll be nice to programs anyway.
>
>
> I'll add a comment, but I'm not convinced how wrong/non-portable this
> usage is.  The [Linux] man page for 'fread' explicitly states that it
> does not distinguish between EOF and error conditions and that an 
> application must use feof() and ferror() to ferret it out.

Since some systems have an EEOF (not us admittedly) it would make sense 
for a portable program to check feof() first before ferror(). The Linux 
man pages obviously reflect Linux :-). But yes it will make programs 
simpler to change eCos this way regardless.

> > > +#include <cyg/fileio/fileio.h>
> >
> > Probably need not include this.
>
> This brought in the prototype for mount().

Oh, oops. In that case what is unistd.h for? Just checking there isn't a 
dependency on something somewhere that isn't explicit.

Jifl
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