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Bug 866269

Summary: dev-cpp/abseil-cpp-20211102.0-r2 fails to compile (lto): error: FLAGS_mistyped_string_flag violates the C++ One Definition Rule [-Werror=odr]
Product: Gentoo Linux Reporter: Agostino Sarubbo <ago>
Component: Current packagesAssignee: No maintainer - Look at if you want to take care of it <maintainer-needed>
Status: CONFIRMED ---    
Severity: normal CC: eschwartz93
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 2022-08-24 05:30:46 UTC

Issue: dev-cpp/abseil-cpp-20211102.0-r2 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

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 1 Agostino Sarubbo gentoo-dev 2022-08-24 05:30:49 UTC
Created attachment 800692 [details]

build log and emerge --info
Comment 2 Agostino Sarubbo gentoo-dev 2022-08-24 05:30:52 UTC
Error(s) that match a know pattern in addition to what has been reported in the summary:

FAILED: bin/absl_flags_flag_test 
/var/tmp/portage/dev-cpp/abseil-cpp-20211102.0-r2/work/abseil-cpp-20211102.0/absl/flags/ error: ‘FLAGS_mistyped_string_flag’ violates the C++ One Definition Rule [-Werror=odr]
Comment 3 Eli Schwartz 2024-04-10 04:47:08 UTC
// This file is used to test the mismatch of the flag type between definition
// and declaration. These are definitions. contains declarations.
#include <string>
#include "absl/flags/flag.h"

ABSL_FLAG(int, mistyped_int_flag, 0, "");
ABSL_FLAG(std::string, mistyped_string_flag, "", "");
ABSL_FLAG(bool, flag_on_separate_file, false, "");
ABSL_RETIRED_FLAG(bool, retired_flag_on_separate_file, false, "");

And in another file:

ABSL_DECLARE_FLAG(int64_t, mistyped_int_flag);
ABSL_DECLARE_FLAG(std::vector<std::string>, mistyped_string_flag);

This, erm, looks very deliberate. Testsuite checks out. :D