Bug 289364

Summary:	'How to get meaningful backtraces in Gentoo' should mention that +glibc-omitfp (default)
Product:	[OLD] Docs on www.gentoo.org	Reporter:	Martin Mokrejš <mmokrejs>
Component:	Other documents	Assignee:	Gentoo Quality Assurance Team <qa>
Status:	RESOLVED OBSOLETE
Severity:	normal	CC:	flameeyes, notordoktor, pva
Priority:	High
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---

Description Martin Mokrejš 2009-10-16 18:38:28 UTC

I have x86 machine and although I have debug code for most application by stacktraces are useless when the dive into glic. I think I found why:

$ tail /etc/portage/package.use
# http://bugs.gentoo.org/82424
# glib-2.10.1 with +glibc-omitfp (default) I get --enable-omitfp
#   --enable-omitfp         build undebuggable optimized library [default=no]
sys-libs/glibc -glibc-omitfp
$


I propose http://www.gentoo.org/proj/en/qa/backtraces.xml?style=printable is 
improved to mention that to get debuggable glibc one needs USE="-glibc-omitfp". 

And, would be fine to explain what kind of debug code enables USE=debug in glibc. I do not see a configure flag of glibc explaining that nor where to look for whatever the debug output would be. Thanks.

Comment 1 Diego Elio Pettenò (RETIRED) gentoo-dev

2009-10-16 22:57:46 UTC

Actually, I don't think omitfp should really mean anything on modern systems with recent GCC; I'll look into it though, just to be sure.

Comment 2 Martin Mokrejš 2009-10-16 23:04:36 UTC

Forgot to say: am on Pentium4-M.

Definitely that was necessary. I could test for older gcc versions. At the moment I have:

$ gcc-config -l
 [1] i686-pc-linux-gnu-3.3.6
 [2] i686-pc-linux-gnu-4.2.4
 [3] i686-pc-linux-gnu-4.3.4
 [4] i686-pc-linux-gnu-4.4.1 *
$

Comment 3 Doktor Notor 2010-03-02 07:48:51 UTC

Hmm, I guess you mean this?

#0  0xb7fde424 in __kernel_vsyscall ()
#1  0xb778b65f in raise () from /lib/libc.so.6
#2  0xb78c4ff4 in ?? () from /lib/libc.so.6
#3  0xb61677f4 in ?? ()
#4  0xb778d027 in abort () from /lib/libc.so.6
#5  0x00000000 in ?? ()

(Trying to debug why gftp crashes on FTPS connections with free(): invalid pointer: