[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: *** %n in writable segment detected ***
From: |
Eric Blake |
Subject: |
Re: *** %n in writable segment detected *** |
Date: |
Fri, 13 Feb 2009 18:39:51 -0700 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.19) Gecko/20081209 Thunderbird/2.0.0.19 Mnenhy/0.7.6.666 |
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
According to Martin Walch on 2/13/2009 5:30 PM:
> When using rather new versions of glibc (2.8...) and gcc (4.3.3), I get an
> ugly warning on the screen during the execution of some configure scripts
> like
> the ones from coreutils or m4. It says:
>
> *** %n in writable segment detected ***
>
> and this is a warning that can not be suppressed by redirecting stdout or
> stderr as glibc opens a new tty.
This is not an autoconf bug. Rather, it is triggered by an overeager
glibc change on a test written by gnulib. Therefore, I'm redirecting this
to the gnulib list, in hopes that Bruno has something to add.
> /* 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;
> }
>
> As soon as basic optimization is turned on (-O1), the warning is thrown.
>
> I think it is a bad idea to get this warning from a configure script. It does
> not appear in config.log but also can not be avoided. It confuses programmers
> and non-programmers. Also, it should be possible to ignore any warning within
> a configure script as it should be save to ignore any warning or error that
> shows up during a check.
>
Agreed. But again, it is not autoconf doing this, but glibc.
- --
Don't work too hard, make some time for fun as well!
Eric Blake address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iEYEARECAAYFAkmWIOcACgkQ84KuGfSFAYB/AgCgu9GMMXbeCRR0aoYTiDjNOPmM
8n8AoME7H7iowzqnXWNZMRH9MThdmiT1
=+cA1
-----END PGP SIGNATURE-----
- Re: *** %n in writable segment detected ***,
Eric Blake <=