Gentoo Archives: gentoo-amd64

From: Duncan <1i5t5.duncan@×××.net>
To: gentoo-amd64@l.g.o
Subject: [gentoo-amd64] Re: Old topic comes round again: -Ox optimizations.
Date: Thu, 03 Nov 2005 15:37:58
Message-Id: pan.2005.11.03.15.27.34.300320@cox.net
In Reply to: Re: [gentoo-amd64] Old topic comes round again: -Ox optimizations. by "Hemmann
1 Hemmann, Volker Armin posted
2 <200511031222.04016.volker.armin.hemmann@××××××××××××.de>, excerpted
3 below, on Thu, 03 Nov 2005 12:22:03 +0100:
4
5 > Os is 'forbidden' for glibc, because there were some gcc bugs, that
6 > miscompiled glibc with Os.
7
8 I've actually run an -Os compiled glibc here (hacked the ebuild to
9 remove the filterflags/replaceflags/stripflags calls) for some time, no
10 noticed issues (tho I haven't tried it with gcc-4.x yet).
11
12 However, it's unsupported, and because glibc is linked by virtually
13 everything, I couldn't be sure whether problems I might have were due to
14 it or not. The thing that switched me back was attempting to trace down
15 why xorg had quite responding to CTRL-ALT-Fx VT-switch commands. I later
16 found out it was a known issue with that version on some configs, fixed in
17 a later version, but glibc is too big a compile (expecially when it's
18 compiled twice, once for 32-bit and once for 64-bit, up to four times for
19 those poor folks running nptl without nptl-only, just the two compiles
20 here, with a dual Opteron, is long, can't imagine four compiles on a
21 single CPU...) to be worth fighting with all the time, I decided.
22
23 Note that for something as universally used as glibc, I'd definitely
24 recommend having a backup root partition with an untouched copy, if you
25 start fooling with removing the strip-flags type stuff.
26
27 Anyway, I expect the -Os problems for glibc were on x86, not amd64.
28 That's apparently been the case in most cases where flags are simply
29 removed without regard for arch, assuming everything else is as broken as
30 32-bit x86, when that's not necessarily the case. Not saying that
31 problems won't occur on amd64, only that I actually expected issues from
32 it and didn't see any.
33
34 As I said, however, I'm done with my -Os fiddling for glibc, for the time
35 being, if only because the hacking to get it and constant wondering if
36 that's the problem any time something strange happens, isn't worth the
37 trouble, for me.
38
39 If folks wish to try it, however, and have a well tested backup boot
40 method in case glibc fails /entirely/, making the existing install
41 entirely unbootable, understand the risks, and have the time to do the
42 compiles, I'd say if you're the type that won't be satisfied until you at
43 least try it and get it out of your blood, so to speak, you might as well
44 do so. It's not as fatal as the dire warnings seem to make it out to be.
45
46 --
47 Duncan - List replies preferred. No HTML msgs.
48 "Every nonfree program has a lord, a master --
49 and if you use the program, he is your master." Richard Stallman in
50 http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html
51
52
53 --
54 gentoo-amd64@g.o mailing list

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