Suppress warnings with latest Apple clang/libc++. #4486
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There is a bad interaction between our empty_base_optimization and libc++'s obsolete implementation of std::equal_to. This involves the deprecated functions std::binary_function and std::unary_function. This commit suppresses the warnings for the use of these functions on libc++, but has to call libc++-specific api (on libc++ only).
shawnxie999
reviewed
Apr 11, 2023
| @@ -189,15 +187,13 @@ class aged_ordered_container | |||
| : public beast::detail::empty_base_optimization<Compare> | |||
| #ifdef _LIBCPP_VERSION | |||
| , | |||
| public std::binary_function<Key, element, bool> | |||
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what would adding the double underscore do?
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This takes advantage of a libc++-only feature. std::binary_function is marked deprecated. But as an implementation technique of libc++, std::__binary_function has the same functionality as std::binary_function but is not marked deprecated. This is done as a hack in libc++ to avoid rewriting things that used to depend on std::binary_function but no longer do. And that hack is reused here in rippled.
If the hack goes away (libc++ comes into conformance), then we will get a compile-time error, and all we'll have to do is remove the code within #ifdef _LIBCPP_VERSION.
shawnxie999
approved these changes
Apr 13, 2023
|
Fails to build on OSX M1, Ventura 13.3.1, apple clang 14.0.0, conan 1.59.0, cmake 3.23.2: |
Include a transition from pre-hack to post-hack.
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Thanks for the detailed report @gregtatcam ! I didn't realize I needed a transition story across different versions of libc++. I've added this as a commit-to-be-merged. If you could rerun your test with this update I would be most grateful. I no longer have the version of libc++ you do, so I'm unable to test against it. |
Sure, no problem. Getting these errors after the update: |
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Thanks @gregtatcam. I actually changed that file but neglected to hit save! |
It builds now! |
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Closing because @thejohnfreeman has a superior solution. |
intelliot
pushed a commit
that referenced
this pull request
Apr 21, 2023
Address issues related to the removal of `std::{u,bi}nary_function` in
C++17 and some warnings with Clang 16. Some warnings appeared with the
upgrade to Apple clang version 14.0.3 (clang-1403.0.22.14.1).
- `std::{u,bi}nary_function` were removed in C++17. They were empty
classes with a few associated types. We already have conditional code
to define the types. Just make it unconditional.
- libc++ checks a cast in an unevaluated context to see if a type
inherits from a binary function class in the standard library, e.g.
`std::equal_to`, and this causes an error when the type privately
inherits from such a class. Change these instances to public
inheritance.
- We don't need a middle-man for the empty base optimization. Prefer to
inherit directly from an empty class than from
`beast::detail::empty_base_optimization`.
- Clang warns when all the uses of a variable are removed by conditional
compilation of assertions. Add a `[[maybe_unused]]` annotation to
suppress it.
- As a drive-by clean-up, remove commented code.
See related work in #4486.
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There is a bad interaction between our empty_base_optimization and libc++'s obsolete implementation of std::equal_to. This involves the deprecated functions std::binary_function and std::unary_function.
This commit suppresses the warnings for the use of these functions on libc++, but has to call libc++-specific api (on libc++ only). This commit has no impact on platforms that do not use libc++.
These warnings do not appear until the upgrade to Apple clang version 14.0.3 (clang-1403.0.22.14.1).
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