[gentoo-commits] repo/gentoo:master commit in: eclass/

[Georgy Yakovlev]

commit:     307f357e8b9ad53abb505b29536788d4a507ccb5
Author:     Georgy Yakovlev <gyakovlev <AT> gentoo <DOT> org>
AuthorDate: Sun Sep  1 06:52:37 2019 +0000
Commit:     Georgy Yakovlev <gyakovlev <AT> gentoo <DOT> org>
CommitDate: Sun Sep  1 19:54:53 2019 +0000
URL:        https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=307f357e

mozcoreconf-v6.eclass: don't force -mminimal-toc on ppc64

This is a really old flag which was needed to compile with
GCC <4.6

I've traced down the existence of this flag here up to
commit 5980a31194da3376ea9dcf804139a2999199508c
Author: Raúl Porcel <armin76 <AT> gentoo.org>
Date:   Sat Mar 15 18:09:25 2008 +0000
Add eclasses for mozilla-firefox-3 and xulrunner-1.9

probably it also was in earlier eclasses.
it was there to fix this kind of bugs: https://bugs.gentoo.org/241900

Problem WAS that on ppc64 .toc1 section could be at most 64KB in size
It's true on GCC versions prior to 4.6 or if mminimal-toc passed on modern gcc

However, since GCC4.6[1] they implemented 3 new TOC models

-mcmodel=small
  uses 16-bit toc offsets, ie. what we had before.

-mcmodel=medium [ the new default ]
  uses 32-bit toc offsets and addresses static data, string constants
  etc. relative to the toc pointer.  Limits data to around 2G.

-mcmodel=large
  uses 32-bit toc offsets, no limit on static data.

By passing  -mminimal-toc on modern GCC we force -mcmodel=small
it means The TOC is limited to 64k.

The default for gcc currently is -mcmodel=medium, with it TOC static
data may grow up to 4G

But here's the problem:
current mozilla builds (thunderbird and firefox) force -O3 optimization
by default, making it very easy to overflow TOC section

{standard input}:1344252: Error: operand out of range \
(0x00000000000178b8 is not between 0xffffffffffff8000 and 0x0000000000007ffc)

Passing -O3 is THE DEFAULT configuration, unless
USE=custom-optimization is set, which voids the warranty =)

So I propose removing this flag from eclass and building with default
model on modern toolchain. Quite unlikely someone tries to build FF/TB
using gcc-4.5, and if they do - they have other problems to solve.

[1] https://gcc.gnu.org/ml/gcc-patches/2010-06/msg00747.html

Acked-by: Jory Pratt <anarchy <AT> gentoo.org>
Signed-off-by: Georgy Yakovlev <gyakovlev <AT> gentoo.org>

 eclass/mozcoreconf-v6.eclass | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/eclass/mozcoreconf-v6.eclass b/eclass/mozcoreconf-v6.eclass
index df08dd19af6..2789e6046b9 100644
--- a/eclass/mozcoreconf-v6.eclass
+++ b/eclass/mozcoreconf-v6.eclass
@@ -229,7 +229,7 @@ mozconfig_init() {
 		append-flags -fPIC
 		;;
 	ppc64)
-		append-flags -fPIC -mminimal-toc
+		append-flags -fPIC
 		# Reduce the memory requirements for linking
 		if use clang ; then
 			# Nothing to do