https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/ Issue: sci-mathematics/glpk-5.0-r1 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 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
Created attachment 796894 [details] build.log build log and emerge --info
I just inspected the code in question and I am not sure if it should count as a false positive or not. I am guessing it may break some compiler optimizations. All the cases reported in minisat.c are `#define` statements, so I would count it as casting rather than aliasing. But it could cause problem when inlining.
Created attachment 798121 [details, diff] 0001-src-minisat-minisat.c-update-types-to-comply-with-al.patch (In reply to François Bissey from comment #2) > I just inspected the code in question and I am not sure if it should count > as a false positive or not. I am guessing it may break some compiler > optimizations. All the cases reported in minisat.c are `#define` statements, > so I would count it as casting rather than aliasing. But it could cause > problem when inlining. I think the problem is that it's casting a pointer to one type (lit) to a pointer to another type (float), and then dereferencing. If so, that's undefined behavior in C even if it happens to work out correctly. I hacked the types to agree and it all worked on the first try, so that gives me some confidence even though I haven't tested it beyond "make check". Patch attached.
Looks good to me.
Reported it upstream...
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=dbda7d259111a90728d62fc56e6d664d5a745f0e commit dbda7d259111a90728d62fc56e6d664d5a745f0e Author: Eli Schwartz <eschwartz93@gmail.com> AuthorDate: 2024-03-05 01:37:21 +0000 Commit: Sam James <sam@gentoo.org> CommitDate: 2024-03-05 04:47:50 +0000 sci-mathematics/glpk: mark as LTO-unsafe, strict-aliasing unsafe It has been reported upstream but no response. Closes: https://bugs.gentoo.org/863047 Signed-off-by: Eli Schwartz <eschwartz93@gmail.com> Signed-off-by: Sam James <sam@gentoo.org> sci-mathematics/glpk/glpk-5.0-r1.ebuild | 11 ++++++++++- sci-mathematics/glpk/glpk-5.0-r2.ebuild | 9 +++++++++ 2 files changed, 19 insertions(+), 1 deletion(-)
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=e9cc5b98df6ccbfc116cd7340f1aa63e56a233cb commit e9cc5b98df6ccbfc116cd7340f1aa63e56a233cb Author: Michael Orlitzky <mjo@gentoo.org> AuthorDate: 2024-10-21 17:04:12 +0000 Commit: Michael Orlitzky <mjo@gentoo.org> CommitDate: 2024-10-24 14:36:14 +0000 sci-mathematics/glpk: steal strict-aliasing patch from Fedora This lets us bring LTO back without having to be responsible for a custom patch. Bug: https://bugs.gentoo.org/863047 Signed-off-by: Michael Orlitzky <mjo@gentoo.org> sci-mathematics/glpk/files/glpk-5.0-aliasing.patch | 89 ++++++++++++++++++++++ .../{glpk-5.0-r2.ebuild => glpk-5.0-r3.ebuild} | 10 +-- 2 files changed, 90 insertions(+), 9 deletions(-)
