Resolves
https://github.com/llvm/llvm-project/issues/76208#issuecomment-2830854351
Quoting the docs of `[[clang::flag_enum]]`:
https://clang.llvm.org/docs/AttributeReference.html#flag-enum
> This attribute can be added to an enumerator to signal to the compiler that it
> is intended to be used as a flag type. This will cause the compiler to assume
> that the range of the type includes all of the values that you can get by
> manipulating bits of the enumerator when issuing warnings.
Ideally, we should still check the upper bounds but for simplicity let's not bother for now.
When merging commit c873f77e87a9ebd02f94d6b9d46e84d43e1ceb38 I didn't
manually rebase it onto the tip of the main branch, so I didn't notice
that the testcase that's added by it needs to be tweaked to account for
the effects of commit 2f29ded4f98e8e1fa26725c618a08082a09b405a (which
was also merged by me a few days ago).
The checker EnumCastOutOfRange verifies the (helpful, but not
standard-mandated) design rule that integer to enum casts should not
produce values that don't have a corresponding enumerator. As it was
improved and cleaned up by recent changes, this commit renames it from
`alpha.cplusplus.EnumCastOutOfRange` to `optin.core.EnumCastOutOfRange`
to reflect that it's no longer alpha quality.
As this checker handles a basic language feature (which is also present
in plain C), I moved it to a "core" subpackage within "optin".
In addition to the renaming, this commit cleans up the documentation in
`checkers.rst` and adds the new example code to a test file to ensure
that it's indeed producing the behavior claimend in the documentation.
...that is causing the bug report when it's converted to the enum type.
This commit only improves the diagnostics and does not affect the set of
reports.
EnumCastOutOfRange checker now reports the name of the enum in the
warning message. Additionally, a note-tag is placed to highlight the
location of the declaration.
The alpha.cplusplus.EnumCastOutOfRange checker previously gave many
false positives because a warning was given if the initializer value
did not appear in the enumerator list.
The strict handling caused std::byte to always give a warning, as it
is implemented as an enum class without any declarators.
Reviewed By: donat.nagy, steakhal
Differential Revision: https://reviews.llvm.org/D153954
Summary: EnumCastOutOfRangeChecker should not perform enum range checks on LValueToRValue casts, since this type of cast does not actually change the underlying type. Performing the unnecessary check actually triggered an assertion failure deeper in EnumCastOutOfRange for certain input (which is captured in the accompanying test code).
Reviewers: #clang, Szelethus, gamesh411, NoQ
Reviewed By: Szelethus, gamesh411, NoQ
Subscribers: NoQ, gamesh411, xazax.hun, baloghadamsoftware, szepet, a.sidorin, mikhail.ramalho, donat.nagy, dkrupp, Charusso, bjope, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D66014
llvm-svn: 369760
