amorfo77/json
1
0
Fork 0
mirror of https://github.com/nlohmann/json.git synced 2026-10-04 05:30:31 +00:00
Code Issues Packages Projects Releases Wiki Activity

Add JSON_DISABLE_TUPLE_REFERENCE_CONVERSION to fix std::tuple conversions

Browse Source 
basic_json can be constructed from std::tuple<json&>, which it turns into
a one-element array. Because of this, std::tuple picks its converting
constructor that converts the whole source tuple instead of the
element-wise one. As a result, std::tuple<const json&> built from
std::forward_as_tuple(j) binds to a temporary (a compile error with libc++,
a dangling reference with other standard libraries), and std::tuple<json>
built the same way holds [j] instead of a copy of j.

The new opt-in macro JSON_DISABLE_TUPLE_REFERENCE_CONVERSION (CMake option
JSON_DisableTupleReferenceConversion) removes the conversion from a
one-element tuple holding a reference to the same basic_json type, so
std::tuple converts element-wise. It is off by default, so existing
behavior is unchanged. It does not change any function body and therefore
is not part of the ABI tag.

Fixes #2226

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-27 17:17:51 +02:00
parent f682cd2ef1
commit c5f1694b01
17 changed files with 296 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/macro_scope.hpp
+4
View File
@@ -916,6 +916,10 @@ void templated_json_throw(ExceptionType exception)
#define JSON_DISABLE_ENUM_SERIALIZATION 0
#endif
#ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
#endif
#ifndef JSON_USE_GLOBAL_UDLS
#define JSON_USE_GLOBAL_UDLS 1
#endif
include/nlohmann/detail/macro_unscope.hpp
+1
View File
@@ -25,6 +25,7 @@
#undef JSON_INLINE_VARIABLE
#undef JSON_NO_UNIQUE_ADDRESS
#undef JSON_DISABLE_ENUM_SERIALIZATION
#undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
#undef JSON_USE_GLOBAL_UDLS
#ifndef JSON_TEST_KEEP_MACROS
include/nlohmann/detail/meta/type_traits.hpp
+12
View File
@@ -636,6 +636,18 @@ template<typename BasicJsonType, typename CompatibleType>
struct is_compatible_type
: is_compatible_type_impl<BasicJsonType, CompatibleType> {};
// a one-element std::tuple holding a reference to BasicJsonType, as created by
// std::forward_as_tuple(j); see JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
template<typename BasicJsonType, typename T>
struct is_basic_json_reference_tuple : std::false_type {};
template<typename BasicJsonType, typename T>
struct is_basic_json_reference_tuple<BasicJsonType, std::tuple<T>>
{
static constexpr bool value =
std::is_reference<T>::value && std::is_same<uncvref_t<T>, BasicJsonType>::value;
};
template<typename BasicJsonType, typename CompatibleArrayType>
struct is_compatible_binary_type
{
include/nlohmann/json.hpp
+6 -1
View File
@@ -1595,7 +1595,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
template < typename CompatibleType,
typename U = detail::uncvref_t<CompatibleType>,
detail::enable_if_t <
!detail::is_basic_json<U>::value && detail::is_compatible_type<basic_json_t, U>::value, int > = 0 >
!detail::is_basic_json<U>::value && detail::is_compatible_type<basic_json_t, U>::value
#if JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
// see https://github.com/nlohmann/json/issues/2226
&& !detail::is_basic_json_reference_tuple<basic_json_t, U>::value
#endif
, int > = 0 >
basic_json(CompatibleType && val) noexcept(noexcept( // NOLINT(bugprone-forwarding-reference-overload,bugprone-exception-escape)
JSONSerializer<U>::to_json(std::declval<basic_json_t&>(),
std::forward<CompatibleType>(val))))