Bug#209136: libc6: printf %#.0g incorrect output

[GOTO Masanori <gotom@debian.or.jp>]

At Sun, 07 Sep 2003 23:51:40 -0400,
Jerry Quinn wrote:
> Philip Blundell writes:
>  > On Sun, 2003-09-07 at 23:29, Jerry Quinn wrote:
>  > > printf("%#.0g", d) gives incorrect results in a couple of cases.
>  > > The first case has an extra 0 at the end.  The second case should be a
>  > > fixed point output according to the manpage, not scientific output.
>  > 
>  > Please supply a test program that illustrates this behaviour.  You need
>  > to explain exactly what output you see, and what (presumably different)
>  > output you feel would be correct.
> 
> I thought I had.  I had used the reportbug attach, but apparently the
> test got lost.  Here's the test program.  The output I get is:
> 
> 0.0010
> 1.e-04
> 
> Reading the manpage for printf makes me believe that these are wrong.
> Note this is on x86, using gcc 2.95.  Using a recent snapshot of gcc
> 3.4 gives the same result.

This is not printf bug, but math issue.  And your variable is not
appropriate.  Please try and report.

> #include <stdio.h>
> #include <stdlib.h>
> 
> int main(void)
> {
>   union fpstruct {
>     double d;
>     long x[2];
>   } fd;
> 
>   fd.x[0]=0x96576b7b; fd.x[1]=0xbf4f519a;
    fd.x[0]=0xd2f1a9fc; fd.x[1]=0x3f50624d;

>   // This should print 0.001
>   printf("%#.0g\n", fd.d);
>  
>   fd.x[0]=0x674bf7a8; fd.x[1]=0x3f19c5d7;
    fd.x[0]=0xeb1c432d; fd.x[1]=0x3f1a36e2;

>   printf("%f\n", fd.d);
>   // This should print 0.0001, since exp is -04 according to manpage
>   printf("%#.0g\n", fd.d);
> }

Regards,
-- gotom