[libc++][bitset] Applied [[nodiscard]]
#170623
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
the
libc++
Member
|
@llvm/pr-subscribers-libcxx Author: Hristo Hristov (H-G-Hristov) Changes
Full diff: https://github.com/llvm/llvm-project/pull/170623.diff 2 Files Affected:
diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index 3453c2fcde71e..82df661ed30ff 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -681,45 +681,54 @@ public:
// element access:
# ifdef _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator[](size_t __p) const {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator[](size_t __p) const {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__p < _Size, "bitset::operator[] index out of bounds");
return __base::__make_ref(__p);
}
# else
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference operator[](size_t __p) const {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference operator[](size_t __p) const {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__p < _Size, "bitset::operator[] index out of bounds");
return __base::__make_ref(__p);
}
# endif
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 reference operator[](size_t __p) {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 reference operator[](size_t __p) {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__p < _Size, "bitset::operator[] index out of bounds");
return __base::__make_ref(__p);
}
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong() const { return __base::to_ulong(); }
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong() const {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong() const {
+ return __base::to_ulong();
+ }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong() const {
return __base::to_ullong();
}
template <class _CharT, class _Traits, class _Allocator>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, _Traits, _Allocator>
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, _Traits, _Allocator>
to_string(_CharT __zero = _CharT('0'), _CharT __one = _CharT('1')) const;
template <class _CharT, class _Traits>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, _Traits, allocator<_CharT> >
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
+ _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, _Traits, allocator<_CharT> >
to_string(_CharT __zero = _CharT('0'), _CharT __one = _CharT('1')) const;
template <class _CharT>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> >
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
+ _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> >
to_string(_CharT __zero = _CharT('0'), _CharT __one = _CharT('1')) const;
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<char, char_traits<char>, allocator<char> >
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
+ _LIBCPP_CONSTEXPR_SINCE_CXX23 basic_string<char, char_traits<char>, allocator<char> >
to_string(char __zero = '0', char __one = '1') const;
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 size_t count() const _NOEXCEPT;
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR size_t size() const _NOEXCEPT { return _Size; }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 size_t count() const _NOEXCEPT;
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR size_t size() const _NOEXCEPT { return _Size; }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool operator==(const bitset& __rhs) const _NOEXCEPT;
# if _LIBCPP_STD_VER <= 17
_LIBCPP_HIDE_FROM_ABI bool operator!=(const bitset& __rhs) const _NOEXCEPT;
# endif
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool test(size_t __pos) const;
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT { return __base::all(); }
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT { return __base::any(); }
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool none() const _NOEXCEPT { return !any(); }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool test(size_t __pos) const;
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT {
+ return __base::all();
+ }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT {
+ return __base::any();
+ }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool none() const _NOEXCEPT { return !any(); }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset operator<<(size_t __pos) const _NOEXCEPT;
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset operator>>(size_t __pos) const _NOEXCEPT;
diff --git a/libcxx/test/libcxx/utilities/template.bitset/nodiscard.verify.cpp b/libcxx/test/libcxx/utilities/template.bitset/nodiscard.verify.cpp
new file mode 100644
index 0000000000000..8fc9b5d402d3b
--- /dev/null
+++ b/libcxx/test/libcxx/utilities/template.bitset/nodiscard.verify.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// <bitset>
+
+// Check that functions are marked [[nodiscard]]
+
+#include <bitset>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+
+void test() {
+ std::bitset<10> bs;
+ const std::bitset<10> cbs;
+
+ bs[0]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cbs[0]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_ulong(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_ullong(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+ struct CharTraits : public std::char_traits<char> {};
+
+ // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_string<char, CharTraits, test_allocator<char>>();
+ // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_string<char, CharTraits>();
+#if !defined(TEST_HAS_NO_WIDE_CHARACTERS)
+ // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_string<wchar_t>();
+#endif
+ // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.to_string();
+
+ bs.count(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.test(0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.all(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.any(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ bs.none(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+}
|
Contributor
Thibault-Monnier
left a comment
Thibault-Monnier
left a comment
There was a problem hiding this comment.
You left out operator<< and operator>>. Is that intentional?
Contributor
Author
Yes. Can you think of an example where it would matter? |
Contributor
|
If we make |
Contributor
I thoght you meant the stream's <<, the bitwise operators should be annoteted. Thanks. |
H-G-Hristov
force-pushed
the
hgh/libcxx/nodiscard-to-bitset
branch
from
22b307f to
100d36f
Compare
`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html - https://wg21.link/bitset
H-G-Hristov
force-pushed
the
hgh/libcxx/nodiscard-to-bitset
branch
from
100d36f to
c47f4d5
Compare
libcxx/test/libcxx/utilities/template.bitset/nodiscard.verify.cpp
Outdated
Show resolved
Hide resolved
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
Thibault-Monnier
approved these changes
Dec 6, 2025
frederick-vs-ja
approved these changes
Dec 6, 2025
Contributor
|
Thanks! |
honeygoyal
pushed a commit
to honeygoyal/llvm-project
that referenced
this pull request
Dec 9, 2025
`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html - https://wg21.link/bitset
84 tasks
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
6 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
[[nodiscard]]should be applied to functions where discarding the return value is most likely a correctness issue.