----- Original Message -----
From: "Kevin Day" <thekevin...@gmail.com>
To: "Hardened LFS Development List" <hlfs-dev@linuxfromscratch.org>
Sent: Saturday, April 24, 2010 3:47 PM
Subject: Re: glibc _FORTIFY_SOURCE=2 and %n in writable segment detected
> On 4/24/10, Gilles Espinasse <g....@free.fr> wrote:
> > Some packages actually coreutils-8.{4,5}, gzip-1.4, m4-1.4.14 print a
> > spurious
> > "%n in writable segment detected" message during configure when glibc
is
> > compiled with _FORTIFY_SOURCE=2
> >
> > This result in gl_cv_func_printf_directive_n=no.
> > If we want to be able to control where the message is printed, we need
to
> > add to the configure command
> > LIBC_FATAL_STDERR_=1 ./configure
> >
> > That way, the message is redirected to stderr as usual.
> > http://sourceware.org/bugzilla/show_bug.cgi?id=9854
> >
> > Gilles
> >
> >
>
> Does this cause any configure tests to fail that should otherwise succeed?
>
> --
> Kevin Day
> --
That's a good question
Author of the test know that test will fail if compiled with
_FORTIFY_SOURCE=2
Just look in configure and comment inside test is clear
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <stdio.h>
#include <string.h>
static char fmtstring[10];
static char buf[100];
int main ()
{
int count = -1;
/* Copy the format string. Some systems (glibc with _FORTIFY_SOURCE=2)
support %n in format strings in read-only memory but not in writable
memory. */
strcpy (fmtstring, "%d %n");
if (sprintf (buf, fmtstring, 123, &count, 33, 44, 55) < 0
|| strcmp (buf, "123 ") != 0
|| count != 4)
return 1;
return 0;
}
_ACEOF
Now the question is :
is it required to support %n in writable memory to support %n format?
If gnulib emulate that system call because test has failed, will the
emulation be better, worst or the same than original from glibc?
Gilles
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