https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/ Issue: media-video/vlc-3.0.17.4 fails to compile (lto). Discovered on: amd64 (internal ref: lto_tinderbox) NOTE: This machine uses lto with CFLAGS=-flto -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing
Created attachment 794429 [details] build.log build log and emerge --info
Error(s) that match a know pattern in addition to what has been reported in the summary: configure: WARNING: Package 'libsystemd', required by 'virtual:world', not found. fatal: not a git repository (or any parent up to mount point /var/tmp) misc/webservices/json.c:134:45: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing[https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wstrict-aliasing]]
Here is a bit of explanation: -Werror=lto-type-mismatch: User to find possible runtime issues in packages. It likely means the package is unsafe to build & use with LTO. For projects using the same identifier but with different types across different files, they must be fixed to be consistent across the codebase. -Werror=odr: Used to find possible runtime issues in packages. These bugs are a problem anyway but may be even worse when combined with LTO. C++ code must comply with the One Definition Rule (ODR) - see https://en.cppreference.com/w/cpp/language/definition#One_Definition_Rule. -Werror=strict-aliasing: Used to find possible runtime issues in packages. These bugs are a problem anyway but may be even worse when combined with LTO. Workarounds: - If upstream is friendly and still active, file a bug upstream. For emulators, codecs, games, or multimedia packages, it may be worth just applying a workaround instead, as upstreams sometimes aren't receptive to these bugs (VALID FOR ALL). - Use the new 'filter-lto' from flag-o-matic.eclass as it's likely to be unsafe with LTO (VALID FOR lto-type-mismatch - odr). - Fix it yourself if interested, of course (VALID FOR ALL). - Append-flags -fno-strict-aliasing (VALID FOR strict-aliasing). - Use memcpy() but a union is sometimes suitable too (VALID FOR strict-aliasing). - -fstrict-aliasing is implied by -O2, so this must be addressed in some form (VALID FOR strict-aliasing). See also: https://marc.info/?l=gentoo-dev&m=165639574126280&w=2
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=3d84addb0089529e1b6ef37cb19db59eb63a02cf commit 3d84addb0089529e1b6ef37cb19db59eb63a02cf Author: Petr Vaněk <arkamar@atlas.cz> AuthorDate: 2022-07-29 11:54:22 +0000 Commit: Joonas Niilola <juippis@gentoo.org> CommitDate: 2022-08-18 07:06:18 +0000 dev-libs/json-parser: new package, add 1.1.0_p20211208 Original version 1.1.0 is from a year 2014, which is quite old. The snapshot is from latest commit 531a49062975 ("Add author of #154 to AUTHORS") in master branch, which contains (among others) two fixes related to strict aliasing. New release is anticipated [1], but it is not clear when it will happen, as the ticket is open for 2 years already. It was necessary to apply one patch proposed as PR [2] to upstream, which changes pkgconfig file installation path from datadir to libdir. This library is currently known to be bundled in multiple packages in ::gentoo, see the corresponding bugs bellow. [1] https://github.com/json-parser/json-parser/issues/82 [2] https://github.com/json-parser/json-parser/pull/164 Bug: https://bugs.gentoo.org/858524 Bug: https://bugs.gentoo.org/861143 Bug: https://bugs.gentoo.org/861371 Signed-off-by: Petr Vaněk <arkamar@atlas.cz> Signed-off-by: Joonas Niilola <juippis@gentoo.org> dev-libs/json-parser/Manifest | 1 + .../files/json-parser-1.1.0-pkgconfig-libdir.patch | 22 ++++++ .../json-parser/json-parser-1.1.0_p20211208.ebuild | 82 ++++++++++++++++++++++ dev-libs/json-parser/metadata.xml | 15 ++++ 4 files changed, 120 insertions(+)
lto_tinderbox has reproduced this issue with version 3.0.17.4-r2 - Updating summary.
Is this still failing with 3.0.18?
I can confirm 3.0.18 is still affected.
3.0.19 is still affected misc/webservices/json.c: In function 'new_value': misc/webservices/json.c:134:45: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-ali asing] 134 | value->_reserved.object_mem = (*(char **) &value->u.object.values) + values_size; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ misc/webservices/json.c: In function 'json_parse_ex': misc/webservices/json.c:343:27: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-ali asing] 343 | (*(json_char **) &top->u.object.values) += string_length + 1;
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=e531bbb35bd0457360b2f178509dac3ce297eb58 commit e531bbb35bd0457360b2f178509dac3ce297eb58 Author: Sam James <sam@gentoo.org> AuthorDate: 2023-11-13 04:43:19 +0000 Commit: Sam James <sam@gentoo.org> CommitDate: 2023-11-13 04:44:10 +0000 media-video/vlc: add 3.0.20 * Add 3.0.20 * Filter LTO and disable strict aliasing (see bug #861143, very longstanding bug upstream) * Drop obsolete -fcommon passing (obsolete since 3.0.18) * Pass ESYSROOT for samba workaround Closes: https://bugs.gentoo.org/861143 Bug: https://bugs.gentoo.org/917274 Signed-off-by: Sam James <sam@gentoo.org> media-video/vlc/Manifest | 1 + media-video/vlc/vlc-3.0.20.ebuild | 517 ++++++++++++++++++++++++++++++++++++ media-video/vlc/vlc-3.0.9999.ebuild | 12 +- media-video/vlc/vlc-9999.ebuild | 12 +- 4 files changed, 528 insertions(+), 14 deletions(-)
Created attachment 874724 [details, diff] vlc-json-strict-aliasing.patch FWIW, media-video/vlc-9999 builds successfully with -flto -Werror=odr -Werror=strict-aliasing -Werror=lto-type-mismatch with this patch (adapted from https://github.com/json-parser/json-parser/commit/161dff8321dfe86d0f657f844d01b9daa97ad33c and https://github.com/json-parser/json-parser/commit/d7b67db02aaa17fcc9bfbc8b60f41c3b677bd5a8).
