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Make diff_frame a member struct that declares its special members

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GCC's -Weffc++ (an error in CI) asks a class with pointer members, a
user constructor and a non-trivial destructor to declare its copy
constructor and copy assignment; diff_frame's vector and basic_json
members make its destructor non-trivial. Declare all five as defaulted,
which also satisfies clang-tidy's special-member-functions check. Leave
their exception specifications implicit: GCC 4.8 rejects an explicit
one that differs from the implicit one, as it does for flatten_task in
#5517.

The converting constructor cannot throw, and is now declared noexcept
for GCC's -Wnoexcept, which flags the emplace_back() under C++26
otherwise. The struct also moves from diff_iteratively() into the class,
like dump_frame in the serializer.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-24 09:38:23 +02:00
parent a3f42f3f95
commit 03d3bc352e
2 changed files with 68 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/json.hpp
+34 -22
View File
@@ -5445,6 +5445,40 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
}
}
/// @brief two arrays or two objects @ref diff_iteratively is diffing
struct diff_frame
{
diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
: source(source_), target(target_), path_length(path_length_)
{}
// declared for GCC's -Weffc++, which asks for them in a class with
// pointer members and a non-trivial destructor; the exception
// specifications are left implicit, as GCC 4.8 rejects explicit ones
// that differ from them
diff_frame(const diff_frame&) = default;
diff_frame(diff_frame&&) = default;
diff_frame& operator=(const diff_frame&) = default;
diff_frame& operator=(diff_frame&&) = default;
~diff_frame() = default;
/// the values being diffed, both arrays or both objects
const basic_json* source;
const basic_json* target;
/// the length of their path in `current_path`
std::size_t path_length;
/// arrays: the next index to diff
std::size_t index = 0;
/// objects: the next member of source to look at
const_iterator member{};
/// objects: the keys common to both, in source's order
std::vector<typename object_t::key_type> common_keys{};
/// objects: the next entry of common_keys
std::size_t next_common = 0;
/// objects: the "add" operations for keys only target has
basic_json added_ops{};
};
/// @ref diff for a @a source nested no more than @ref diff_depth_limit levels deep
static basic_json diff_recursively(const basic_json& source, const basic_json& target,
const string_t& path)
@@ -5700,28 +5734,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
// diff_recursively. The path of the values being diffed is kept in
// one buffer that grows and shrinks with the stack, rather than in a
// new string per level.
struct diff_frame
{
diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_)
: source(source_), target(target_), path_length(path_length_)
{}
/// the values being diffed, both arrays or both objects
const basic_json* source;
const basic_json* target;
/// the length of their path in `current_path`
std::size_t path_length;
/// arrays: the next index to diff
std::size_t index = 0;
/// objects: the next member of source to look at
const_iterator member{};
/// objects: the keys common to both, in source's order
std::vector<typename object_t::key_type> common_keys{};
/// objects: the next entry of common_keys
std::size_t next_common = 0;
/// objects: the "add" operations for keys only target has
basic_json added_ops{};
};
std::vector<diff_frame> stack;
string_t current_path = path;
single_include/nlohmann/json.hpp
+34 -22
View File
@@ -29804,6 +29804,40 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
}
}
/// @brief two arrays or two objects @ref diff_iteratively is diffing
struct diff_frame
{
diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
: source(source_), target(target_), path_length(path_length_)
{}
// declared for GCC's -Weffc++, which asks for them in a class with
// pointer members and a non-trivial destructor; the exception
// specifications are left implicit, as GCC 4.8 rejects explicit ones
// that differ from them
diff_frame(const diff_frame&) = default;
diff_frame(diff_frame&&) = default;
diff_frame& operator=(const diff_frame&) = default;
diff_frame& operator=(diff_frame&&) = default;
~diff_frame() = default;
/// the values being diffed, both arrays or both objects
const basic_json* source;
const basic_json* target;
/// the length of their path in `current_path`
std::size_t path_length;
/// arrays: the next index to diff
std::size_t index = 0;
/// objects: the next member of source to look at
const_iterator member{};
/// objects: the keys common to both, in source's order
std::vector<typename object_t::key_type> common_keys{};
/// objects: the next entry of common_keys
std::size_t next_common = 0;
/// objects: the "add" operations for keys only target has
basic_json added_ops{};
};
/// @ref diff for a @a source nested no more than @ref diff_depth_limit levels deep
static basic_json diff_recursively(const basic_json& source, const basic_json& target,
const string_t& path)
@@ -30059,28 +30093,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
// diff_recursively. The path of the values being diffed is kept in
// one buffer that grows and shrinks with the stack, rather than in a
// new string per level.
struct diff_frame
{
diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_)
: source(source_), target(target_), path_length(path_length_)
{}
/// the values being diffed, both arrays or both objects
const basic_json* source;
const basic_json* target;
/// the length of their path in `current_path`
std::size_t path_length;
/// arrays: the next index to diff
std::size_t index = 0;
/// objects: the next member of source to look at
const_iterator member{};
/// objects: the keys common to both, in source's order
std::vector<typename object_t::key_type> common_keys{};
/// objects: the next entry of common_keys
std::size_t next_common = 0;
/// objects: the "add" operations for keys only target has
basic_json added_ops{};
};
std::vector<diff_frame> stack;
string_t current_path = path;