[ECOS]A question about printf

[ECOS]A question about printf

[Andrea Acquaviva]

Hi,

I have a question about printf().
I noted that if I make two consecutive call to prinf or fprintf
functions
in my executables (also a simply modified hello world program), the
execution stops at the second function call, namely the second printf()
doesn't works at all.

What's the reason of this?

Thanks,
Andrea.


--
Ing. Andrea Acquaviva
D.E.I.S. - Universita' di Bologna
V.le Risorgimento, 2    40136 BOLOGNA (ITALY)
Tel: (+39) 051 20 93787 Fax: (+39) 051 2093786

Re: [ECOS]A question about printf

[Lewin A.R.W. Edwards]

Hello Andrea,

>I have a question about printf().
>I noted that if I make two consecutive call to prinf or fprintf
>functions in my executables (also a simply modified hello world program), the
>execution stops at the second function call, namely the second printf()
>doesn't works at all.

I was debugging some SmartMedia code today in eCos and noticed that the 
following code:

int i;
for (i=0;i<4096;i++) {
int k;
// some processing which assigns a value to k
printf("** Found logical block %d at physical block %d ",i, k);
}

would skip some of the last bytes of the output. However, if I added \n to 
the end of the printf format string, then all output is OK.

Looks like a buffering issue of some kind perhaps, try adding \n to the end 
of your printf strings and see if that fixes it.

=== Lewin A.R.W. Edwards (Embedded Engineer)
Work: http://www.digi-frame.com/
Personal: http://www.zws.com/ and http://www.larwe.com/

Re: [ECOS]A question about printf

[Jonathan Larmour]

"Lewin A.R.W. Edwards" wrote:
> 
> printf("** Found logical block %d at physical block %d ",i, k);
> }
> 
> would skip some of the last bytes of the output. However, if I added \n to
> the end of the printf format string, then all output is OK.
> 
> Looks like a buffering issue of some kind perhaps, try adding \n to the end
> of your printf strings and see if that fixes it.

This is completely correct for line-buffered output and is mandated by the
ISO C standard. There is no bug in this case.

Jifl
-- 
Red Hat, 35 Cambridge Place, Cambridge, UK. CB2 1NS  Tel: +44 (1223) 728762
"Plan to be spontaneous tomorrow."  ||  These opinions are all my own fault

Re: [ECOS]A question about printf

[Lewin A.R.W. Edwards]

Hi Jonathan,

> > printf("** Found logical block %d at physical block %d ",i, k);
> >
> > Looks like a buffering issue of some kind perhaps, try adding \n to the end
>
>This is completely correct for line-buffered output and is mandated by the
>ISO C standard. There is no bug in this case.

Well, please note that I didn't call it a bug, I called it an issue (or 
perhaps "behavior") and although I didn't realize it was part of ISO, I 
have dealt with the issue before and so it didn't bother me. In my case 
anyway it was only exposed by an outright bug in my code :)

=== Lewin A.R.W. Edwards (Embedded Engineer)
Work: http://www.digi-frame.com/
Personal: http://www.zws.com/ and http://www.larwe.com/