1 |
Hi, I just had an unpleasant experience with -ffast-math and GCC 4.1.1 |
2 |
(it borked my LDAP authentication on several systems which worked with |
3 |
the same CFLAGS as long as GCC 3.4.6 was used). |
4 |
|
5 |
There is a lot of material out there about CFLAGS and Gentoo (google |
6 |
returns 387000 pages) but what's working for someone might not for |
7 |
another. There are flags that work for a GCC version and most ebuilds |
8 |
and don't work with another GCC version (my unfortunate experience) or |
9 |
some ebuilds. Flag combination/architecture/LDFLAGS might be an issue too. |
10 |
|
11 |
There are already good resources (http://gentoo-wiki.com/CFLAGS_matrix |
12 |
was mentioned to me by robbat2) but they may not be advertised enough. |
13 |
I'd like to propose a paragraph to the GWN editor which presents some |
14 |
gotchas and good references on the subject. |
15 |
|
16 |
Here's a draft for review. You're welcomed to expand on the subject. |
17 |
|
18 |
--- Draft BEGIN --- |
19 |
<section> |
20 |
<title>CFLAGS</title> |
21 |
<body> |
22 |
|
23 |
<p> |
24 |
Being able to tune the CFLAGS is part of one of the core principles of |
25 |
Gentoo: let the user be in control. Being in control brings both |
26 |
benefits and problems and CFLAGS tuning is not an exception. |
27 |
</p> |
28 |
<p> |
29 |
The recent upgrade to gcc-4.1.1 for x86 and amd64 users changed the |
30 |
landscape. Users that spent some time tuning their CFLAGS with gcc-3.4.6 |
31 |
might find out that an upgrade to gcc-4.1.1 leaves them with an unstable |
32 |
system. Example of this are : |
33 |
<ul> |
34 |
<li>nss_ldap stopped working with -ffast-math</li> |
35 |
<li>...</li> |
36 |
</ul> |
37 |
</p> |
38 |
<p> |
39 |
Users with unsupported CFLAGS (see the <uri |
40 |
link='http://gentoo-wiki.com/CFLAGS_matrix'>CFLAGS matrix</uri> for |
41 |
example) might want to return to safe CFLAGS (see <uri |
42 |
link='http://gentoo-wiki.com/Safe_Cflags'>Safe CFLAGS</uri>) if recent |
43 |
updates caused them stability problems. On the other hand, more |
44 |
adventurous users might want to experiment with CFLAGS that didn't work |
45 |
properly with gcc-3.4.6... As always, the user is in control. |
46 |
</p> |
47 |
</body> |
48 |
</section> |
49 |
--- Draft END --- |
50 |
|
51 |
If possible, I'd like to expand the list of 3.4.6 -> 4.1.1 upgrade |
52 |
problems which are linked to experimental CFLAGS. If you want to expand |
53 |
the subject to cover other tuning/stability gotchas that recent updates |
54 |
might have brought into the light, please feel free to do so. As English |
55 |
is not my native tongue, feel free to spell check too. |
56 |
|
57 |
Cheers, |
58 |
|
59 |
Lionel. |
60 |
-- |
61 |
gentoo-dev@g.o mailing list |