Bug#346437: dietlibc-dev: fflush(NULL) flushes input-only streams (stdin)

[Eric Wong]

Gerrit Pape <[EMAIL PROTECTED]> wrote:
> On Sat, Jan 07, 2006 at 03:33:43PM -0800, Eric Wong wrote:
> > fflush(NULL) seems to flush the stdin stream, as well as any open
> > streams it can find, regardless of whether or not it's a writeable
> > stream.   According to the fflush manpage, this is wrong:
> > 
> > If  the  stream  argument  is  NULL,  fflush()  flushes all open
> > output streams.
> > 
> > You can see this behavior with the test program I've included below, and
> > then test it again by commenting out the fflush(NULL) call in it to see
> > the difference.
> 
> Hi Eric, while I can see from the dietlibc sources that indeed the input
> streams including stdin are fflushed, I currently cannot see the impact.
> 
> Can you please show me how to use your test program to see a difference?

Just use it to read a text file from stdin.  You'll note that there are
missing lines when compiled with dietlibc
 
> > #include 
> > #include 
> > 
> > int main (void)
> > {
> > char buf[4096];
> > while (fgets(buf,4096,stdin)) {
> > /* this can also be fwrite/fprintf: */
> > write(1,buf,strlen(buf));
> > 
> > /* you can comment this out to compare */
> > fflush(NULL);
> > }
> > 
> > return 0;
> > }
> > 
> > /* EOF */
> 

-- 
Eric Wong


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Bug#346437: dietlibc-dev: fflush(NULL) flushes input-only streams (stdin)

[Gerrit Pape]

On Sat, Jan 07, 2006 at 03:33:43PM -0800, Eric Wong wrote:
> fflush(NULL) seems to flush the stdin stream, as well as any open
> streams it can find, regardless of whether or not it's a writeable
> stream.   According to the fflush manpage, this is wrong:
> 
>   If  the  stream  argument  is  NULL,  fflush()  flushes all open
>   output streams.
> 
> You can see this behavior with the test program I've included below, and
> then test it again by commenting out the fflush(NULL) call in it to see
> the difference.

Hi Eric, while I can see from the dietlibc sources that indeed the input
streams including stdin are fflushed, I currently cannot see the impact.

Can you please show me how to use your test program to see a difference?

Thanks, Gerrit.


> #include 
> #include 
> 
> int main (void)
> {
>   char buf[4096];
>   while (fgets(buf,4096,stdin)) {
>   /* this can also be fwrite/fprintf: */
>   write(1,buf,strlen(buf));
>   
>   /* you can comment this out to compare */
>   fflush(NULL);
>   }
> 
>   return 0;
> }
> 
> /* EOF */


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Bug#346437: dietlibc-dev: fflush(NULL) flushes input-only streams (stdin)

[Eric Wong]

Package: dietlibc-dev
Version: 0.29-8
Severity: normal


fflush(NULL) seems to flush the stdin stream, as well as any open
streams it can find, regardless of whether or not it's a writeable
stream.   According to the fflush manpage, this is wrong:

If  the  stream  argument  is  NULL,  fflush()  flushes all open
output streams.

You can see this behavior with the test program I've included below, and
then test it again by commenting out the fflush(NULL) call in it to see
the difference.

#include 
#include 

int main (void)
{
char buf[4096];
while (fgets(buf,4096,stdin)) {
/* this can also be fwrite/fprintf: */
write(1,buf,strlen(buf));

/* you can comment this out to compare */
fflush(NULL);
}

return 0;
}

/* EOF */

-- System Information:
Debian Release: testing/unstable
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.14.2-g54f4bf28
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) (ignored: LC_ALL set to C)

dietlibc-dev depends on no packages.

Versions of packages dietlibc-dev recommends:
pn  dietlibc   (no description available)

-- no debconf information


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