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Bug 858377

Summary: dev-util/gperf-3.1-r1 fails to compile (lto): keyword-list.icc:50:11: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
Product: Gentoo Linux Reporter: Agostino Sarubbo <ago>
Component: Current packagesAssignee: Gentoo's Team for Core System packages <base-system>
Status: CONFIRMED ---    
Severity: normal CC: anthonyryan1, kocelfc
Priority: Normal    
Version: unspecified   
Hardware: All   
OS: Linux   
Package list:
Runtime testing required: ---
Bug Depends on:    
Bug Blocks: 618550    
Attachments: build.log

Description Agostino Sarubbo gentoo-dev 2022-07-16 15:39:34 UTC

Issue: dev-util/gperf-3.1 fails to compile (lto).
Discovered on: amd64 (internal ref: lto_tinderbox)

This machine uses lto with CFLAGS=-flto -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing
Comment 1 Agostino Sarubbo gentoo-dev 2022-07-16 15:39:36 UTC
Created attachment 791738 [details]

build log and emerge --info
Comment 2 Agostino Sarubbo gentoo-dev 2022-07-26 09:01:29 UTC
Here is a bit of explanation:

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.

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

Used to find possible runtime issues in packages. These bugs are a problem anyway but may be even worse when combined with LTO.

- 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:
Comment 3 Agostino Sarubbo gentoo-dev 2022-09-26 08:44:00 UTC
lto_tinderbox has reproduced this issue with version 3.1-r1 - Updating summary.
Comment 4 Kim B. Sindalsen 2023-01-15 22:55:57 UTC
Not restricted to LTO - same on non-lto

cd src; make all
make[1]: Entering directory '/var/tmp/portage/dev-util/gperf-3.1-r1/work/gperf-3.1/src'
x86_64-pc-linux-gnu-g++ -O2 -pipe -march=native -Werror=strict-aliasing -Werror=odr -Werror=lto-type-mismatch -flifetime-dse=1 -I. -I./../lib -c ./
x86_64-pc-linux-gnu-g++ -O2 -pipe -march=native -Werror=strict-aliasing -Werror=odr -Werror=lto-type-mismatch -flifetime-dse=1 -I. -I./../lib -c ./
x86_64-pc-linux-gnu-g++ -O2 -pipe -march=native -Werror=strict-aliasing -Werror=odr -Werror=lto-type-mismatch -flifetime-dse=1 -I. -I./../lib -c ./
x86_64-pc-linux-gnu-g++ -O2 -pipe -march=native -Werror=strict-aliasing -Werror=odr -Werror=lto-type-mismatch -flifetime-dse=1 -I. -I./../lib -c ./
x86_64-pc-linux-gnu-g++ -O2 -pipe -march=native -Werror=strict-aliasing -Werror=odr -Werror=lto-type-mismatch -flifetime-dse=1 -I. -I./../lib -c ./
In file included from ./keyword-list.h:78,
                 from ./
./keyword-list.icc: In member function ‘KeywordExt_List*& KeywordExt_List::rest()’:
./keyword-list.icc:50:11: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   50 |   return *reinterpret_cast<KeywordExt_List**>(&_cdr);
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: some warnings being treated as errors
make[1]: *** [Makefile:107: keyword-list.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory '/var/tmp/portage/dev-util/gperf-3.1-r1/work/gperf-3.1/src'
make: *** [Makefile:34: all] Error 2
 * ERROR: dev-util/gperf-3.1-r1::gentoo failed (compile phase):
 *   emake failed
 * If you need support, post the output of `emerge --info '=dev-util/gperf-3.1-r1::gentoo'`,
 * the complete build log and the output of `emerge -pqv '=dev-util/gperf-3.1-r1::gentoo'`.
 * The complete build log is located at '/var/log/portage/dev-util:gperf-3.1-r1:20230115-225352.log'.
 * For convenience, a symlink to the build log is located at '/var/tmp/portage/dev-util/gperf-3.1-r1/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/dev-util/gperf-3.1-r1/temp/environment'.
 * Working directory: '/var/tmp/portage/dev-util/gperf-3.1-r1/work/gperf-3.1'
 * S: '/var/tmp/portage/dev-util/gperf-3.1-r1/work/gperf-3.1'

>>> Failed to emerge dev-util/gperf-3.1-r1, Log file:
Comment 5 Pietro 2023-08-27 10:43:48 UTC
Unfortunately I can reproduce the issue as well.

I created the following nolto.conf file and added the program in question to nolto.conf but made no difference

CFLAGS="${CFLAGS} -fno-lto"
FCFLAGS="${FCFLAGS} -fno-lto"
FFLAGS="${FFLAGS} -fno-lto"

I am using the following COMMON_FLAGS in make.conf:
COMMON_FLAGS="-march=alderlake -O2 -pipe -flto -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing"

Any help to fix / bybass the error would be appreciated.

Comment 6 Kostadin Shishmanov 2023-08-27 10:54:25 UTC
A workaround would be to make an env file which appends -fno-strict-aliasing for all the packages that fail because of that error until they are fixed upstream.