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Re-enable bugprone-use-after-move/hicpp-invalid-access-moved

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These two checks (and portability-template-virtual-member-function)
were disabled in #4489 (November 2024) "only removed to get the CI
going". portability-template-virtual-member-function is a separate,
still-open cleanup (#5725 item 3 on its own branch) and stays
disabled here; this commit only re-enables the move/forward checks
and cleans up what they flag on this branch.

The move constructor (json.hpp) already casts to the base type
instead of forwarding the whole object (#5724 item 9), so it no
longer trips either check. The at(KeyType&&) double-forward this
check used to flag was reduced to a single forward with the
now-unforwarded reuse annotated by a NOLINTNEXTLINE in #5724 item 3's
object_at() helper (clang-tidy 22 still flags that reuse even after a
single forward; see that commit's message). What is left here:

- from_json_inplace_array_impl(), from_json_tuple_impl_base() and the
  std::pair overload of from_json_tuple_impl() forwarded j into every
  j.at(...) call in a pack expansion or a pair of calls. at() has no
  ref-qualified overloads, so the forward was a no-op; call j.at(...)
  directly.
- container_input_adapter_factory::create() forwards container twice
  on purpose, into begin() and end(), so both see the same value
  category and produce matching iterator types. Annotate it with
  NOLINTNEXTLINE and a comment instead of changing it.
- unit-class_parser.cpp's "move constructor resets the moved-from
  value to npos" test still pointed at the pre-static_cast move
  constructor by line number and mentioned the cppcheck-suppress
  annotation that #5724 item 9 already removed; update the comment.

No behavior change anywhere in include/. Verified with clang-tidy 22.1.8
(Docker silkeh/clang:22, --platform linux/amd64) against a TU including
json.hpp with the repo's .clang-tidy: bugprone-use-after-move and
hicpp-invalid-access-moved report nothing unsuppressed.

Overlaps #5737 (open PR for the rest of #5725 item 3: the
from_json.hpp/input_adapters.hpp cleanup above, and
portability-template-virtual-member-function), which currently keeps
both checks disabled pending this move-constructor change; whichever
of this commit and that PR lands second will need a small rebase of
.clang-tidy.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-30 19:05:07 +02:00
parent 3e771c2ad7
commit 09d41a894b
5 changed files with 14 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
.clang-tidy
+1 -3
View File
@@ -1,11 +1,9 @@
# TODO: The first three checks are only removed to get the CI going. They have to be addressed at some point.
# TODO: portability-template-virtual-member-function is only removed to get the CI going. It has to be addressed at some point.
# TODO: portability-avoid-pragma-once: should be fixed eventually
Checks: '*,
-portability-template-virtual-member-function,
-bugprone-use-after-move,
-hicpp-invalid-access-moved,
-altera-id-dependent-backward-branch,
-altera-struct-pack-align,
include/nlohmann/detail/conversions/from_json.hpp
+4 -4
View File
@@ -353,7 +353,7 @@ template < typename BasicJsonType, typename T, std::size_t... Idx >
std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(BasicJsonType&& j,
identity_tag<std::array<T, sizeof...(Idx)>> /*unused*/, index_sequence<Idx...> /*unused*/)
{
return { { std::forward<BasicJsonType>(j).at(Idx).template get<T>()... } };
return { { j.at(Idx).template get<T>()... } };
}
template < typename BasicJsonType, typename T, std::size_t N >
@@ -502,7 +502,7 @@ using tuple_type = std::tuple < decltype(from_json_tuple_get_impl(std::declval<B
template<std::size_t PTagValue, typename... Args, typename BasicJsonType, std::size_t... Idx>
tuple_type<PTagValue, BasicJsonType, Args...> from_json_tuple_impl_base(BasicJsonType&& j, index_sequence<Idx...> /*unused*/)
{
return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(std::forward<BasicJsonType>(j).at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(j.at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
}
template<std::size_t PTagValue, typename BasicJsonType>
@@ -514,8 +514,8 @@ std::tuple<> from_json_tuple_impl_base(BasicJsonType& /*unused*/, index_sequence
template < typename BasicJsonType, class A1, class A2 >
std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
{
return {std::forward<BasicJsonType>(j).at(0).template get<A1>(),
std::forward<BasicJsonType>(j).at(1).template get<A2>()};
return {j.at(0).template get<A1>(),
j.at(1).template get<A2>()};
}
template<typename BasicJsonType, typename A1, typename A2>
include/nlohmann/detail/input/input_adapters.hpp
+1
View File
@@ -763,6 +763,7 @@ struct container_input_adapter_factory< ContainerType,
static adapter_type create(ContainerType&& container)
{
// NOLINTNEXTLINE(bugprone-use-after-move,hicpp-invalid-access-moved) forwarded twice on purpose, so begin() and end() see the same value category and yield matching iterator types
return input_adapter(begin(std::forward<ContainerType>(container)), end(std::forward<ContainerType>(container)));
}
};
single_include/nlohmann/json.hpp
+5 -4
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@@ -5849,7 +5849,7 @@ template < typename BasicJsonType, typename T, std::size_t... Idx >
std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(BasicJsonType&& j,
identity_tag<std::array<T, sizeof...(Idx)>> /*unused*/, index_sequence<Idx...> /*unused*/)
{
return { { std::forward<BasicJsonType>(j).at(Idx).template get<T>()... } };
return { { j.at(Idx).template get<T>()... } };
}
template < typename BasicJsonType, typename T, std::size_t N >
@@ -5998,7 +5998,7 @@ using tuple_type = std::tuple < decltype(from_json_tuple_get_impl(std::declval<B
template<std::size_t PTagValue, typename... Args, typename BasicJsonType, std::size_t... Idx>
tuple_type<PTagValue, BasicJsonType, Args...> from_json_tuple_impl_base(BasicJsonType&& j, index_sequence<Idx...> /*unused*/)
{
return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(std::forward<BasicJsonType>(j).at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(j.at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
}
template<std::size_t PTagValue, typename BasicJsonType>
@@ -6010,8 +6010,8 @@ std::tuple<> from_json_tuple_impl_base(BasicJsonType& /*unused*/, index_sequence
template < typename BasicJsonType, class A1, class A2 >
std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
{
return {std::forward<BasicJsonType>(j).at(0).template get<A1>(),
std::forward<BasicJsonType>(j).at(1).template get<A2>()};
return {j.at(0).template get<A1>(),
j.at(1).template get<A2>()};
}
template<typename BasicJsonType, typename A1, typename A2>
@@ -8306,6 +8306,7 @@ struct container_input_adapter_factory< ContainerType,
static adapter_type create(ContainerType&& container)
{
// NOLINTNEXTLINE(bugprone-use-after-move,hicpp-invalid-access-moved) forwarded twice on purpose, so begin() and end() see the same value category and yield matching iterator types
return input_adapter(begin(std::forward<ContainerType>(container)), end(std::forward<ContainerType>(container)));
}
};
tests/src/unit-class_parser.cpp
+3 -5
View File
@@ -2525,12 +2525,10 @@ TEST_CASE("diagnostic positions: value lifetime, input adapters, and SAX")
SECTION("move constructor resets the moved-from value to npos")
{
// basic_json(basic_json&&) (json.hpp, around line 1265) copies
// basic_json(basic_json&&) (json.hpp, around line 1944) copies
// other's start_position/end_position into *this and then resets
// other's to npos (see the cppcheck-suppress[accessForwarded]
// annotation there, which flags this reset as worth a second
// look). Only the top-level moved-from value is affected; its
// (moved-away) children are gone along with it.
// other's to npos. Only the top-level moved-from value is
// affected; its (moved-away) children are gone along with it.
const std::string s = R"({"a":1,"b":[1,2,3]})";
json a = json::parse(s);
const auto a_start = a.start_pos();