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Author SHA1 Message Date
Niels Lohmann cc749ac699 Keep full byte2 x byte3 combinatorics in the wrong-fourth-byte sections
The maintainer wants exhaustive coverage of every byte combination here
rather than the representative-prefix reduction, matching the style of
the sibling "wrong second/third byte" sections in the same files.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-05 23:18:51 +02:00
Niels Lohmann 1c6ca81b8a Fix dead ill-formed-fourth-byte UTF-8 test sections (byte3/byte4 typo)
The "ill-formed: wrong fourth byte" SECTIONs in unit-unicode3.cpp,
unit-unicode4.cpp, and unit-unicode5.cpp guarded their loop with a check
on byte3 instead of byte4. Since the enclosing loop already restricts
byte3 to its valid range, the guard was always true and the section's
"continue" fired unconditionally, so check_utf8string()/check_utf8dump()
were never actually invoked for a malformed fourth byte.

Fixing the guard naively (byte3 -> byte4) would also have swept the full
byte2 x byte3 combinatorics for every byte4 value, adding millions of
redundant iterations: the lexer validates continuation bytes strictly in
sequence with early exit (see next_byte_in_range() in lexer.hpp), so once
byte2/byte3 are within their valid range, the byte4 outcome does not
depend on which valid byte2/byte3 values were chosen. Instead, byte2 and
byte3 are now held to a small hedge of representative valid prefixes
(range corners plus a midpoint) while byte4 is still swept exhaustively
over its full 0x00-0xFF range, since that is the actual property under
test. Also fixed the garbled "skip fourth second byte" comment in
unit-unicode3.cpp.

Verified offline: before the fix, the "wrong fourth byte" subcase
executes 0 assertions in all three files (proving it was dead code);
after the fix, it executes 11520 (unicode3), 34560 (unicode4), and 11520
(unicode5) assertions, and a deliberately reintroduced bug in the
lexer's byte4 range check causes it to fail (proving it is now
meaningful). Total per-file assertion counts grow by the same small
amounts, not by millions, and all other sections in these files still
pass unchanged.

Fixes #5416

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-05 23:05:42 +02:00
7 changed files with 32 additions and 358 deletions
+14 -121
View File
@@ -3573,7 +3573,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
{
using std::swap;
swap(*(m_data.m_value.array), other);
set_parents();
}
else
{
@@ -3590,7 +3589,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
{
using std::swap;
swap(*(m_data.m_value.object), other);
set_parents();
}
else
{
@@ -5159,139 +5157,34 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
case value_t::object:
{
// first pass: record, for every source key, whether it is
// common to both objects (in source's iteration order) or
// was deleted (i.e., in source but not in target) -- this is
// a by-product of the target.find() call already needed to
// tell the two cases apart, so it adds no extra lookups. The
// "remove" ops themselves are emitted later, interleaved
// with the recursive per-key diffs in the fast path below,
// to match source's original iteration order (as the
// original, pre-reordering-aware implementation did) instead
// of grouping all removes before all recursive diffs.
std::vector<typename object_t::key_type> common_keys_source_order;
// first pass: traverse this object's elements
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
// escape the key name to be used in a JSON patch
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
if (target.find(it.key()) != target.end())
{
common_keys_source_order.push_back(it.key());
}
}
// second pass: find keys that were added (i.e., in target but
// not in source), and record the keys common to both, in
// target's iteration order -- again a by-product of the
// source.find() call already needed to detect added keys. At
// the same time, determine whether every added key comes
// after every common key in target's order (a precondition
// for the fast path below, which only ever appends new keys
// at the very end): for an object_t whose iteration order is
// a pure function of the key set (e.g. the default std::map,
// which always iterates in sorted key order), the order
// check further below is always true and this whole
// mechanism is effectively a no-op; it only matters for a
// reorderable object_t such as the one backing `ordered_json`.
// patch ops for keys that were added (i.e., in target but not
// in source); built here so the fast path below can reuse
// them without a second source.find() per target key. Only
// used by the fast path -- the slow (reordering) path
// rebuilds "add" ops for every key itself.
std::vector<typename object_t::key_type> common_keys_target_order;
basic_json added_ops(value_t::array);
bool new_keys_form_suffix = true;
bool seen_new_key = false;
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
seen_new_key = true;
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
added_ops.push_back(
{
{"op", "add"}, {"path", path_key},
{"value", it.value()}
});
// recursive call to compare object values at key it
auto temp_diff = diff(it.value(), target[it.key()], path_key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
}
else
{
common_keys_target_order.push_back(it.key());
if (seen_new_key)
{
new_keys_form_suffix = false;
}
}
}
if (common_keys_source_order == common_keys_target_order && new_keys_form_suffix)
{
// fast path: order of common keys already matches (or the
// object_t's iteration order does not depend on
// insertion history), so a plain per-key recursive diff
// is correct and minimal, as before. common_keys_source_order
// is, by construction, the subsequence of source's keys
// that are common to both objects, in source's iteration
// order -- so it can be walked in lockstep with `source`
// using a cheap key comparison instead of another lookup.
// Deleted keys (those source keys not in common_keys_source_order)
// are interleaved here too, in source's original order, to
// match the historical (pre-reordering-aware) output order.
auto common_it = common_keys_source_order.cbegin();
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
auto temp_diff = diff(it.value(), target[it.key()], path_key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
++common_it;
}
else
{
// found a key that is not in target -> remove it
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
}
// append the "add" ops for brand-new keys collected above
// during the pass over target -- no second source.find()
// per target key needed
result.insert(result.end(), added_ops.begin(), added_ops.end());
}
else
{
// slow path: the common keys are in a different relative
// order in source and target (only possible for a
// reorderable object_t like ordered_map). Building a
// minimal reordering patch is a nontrivial (LCS-like)
// problem; instead, remove every source key -- both
// deleted keys (which must be removed regardless) and
// common keys (removed so they can be re-added in
// target's order) -- and re-add every key that should
// remain, with its final target value, in target's
// order. basic_json::patch()'s "add" operation on an
// object uses operator[], which appends at the end for a
// vector-backed insertion-ordered map when the key does
// not already exist -- so removing a key and then adding
// it moves it to the end, fixing its position.
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
// found a key that is not in o -> remove it
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
}
// add every key that is either common (just removed
// above) or brand new, in target's iteration order, so
// that the final order after applying the patch matches
// target exactly
for (auto it = target.cbegin(); it != target.cend(); ++it)
// second pass: traverse other object's elements
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
// found a key that is not in this -> add it
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(
{
+14 -121
View File
@@ -25001,7 +25001,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
{
using std::swap;
swap(*(m_data.m_value.array), other);
set_parents();
}
else
{
@@ -25018,7 +25017,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
{
using std::swap;
swap(*(m_data.m_value.object), other);
set_parents();
}
else
{
@@ -26587,139 +26585,34 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
case value_t::object:
{
// first pass: record, for every source key, whether it is
// common to both objects (in source's iteration order) or
// was deleted (i.e., in source but not in target) -- this is
// a by-product of the target.find() call already needed to
// tell the two cases apart, so it adds no extra lookups. The
// "remove" ops themselves are emitted later, interleaved
// with the recursive per-key diffs in the fast path below,
// to match source's original iteration order (as the
// original, pre-reordering-aware implementation did) instead
// of grouping all removes before all recursive diffs.
std::vector<typename object_t::key_type> common_keys_source_order;
// first pass: traverse this object's elements
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
// escape the key name to be used in a JSON patch
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
if (target.find(it.key()) != target.end())
{
common_keys_source_order.push_back(it.key());
}
}
// second pass: find keys that were added (i.e., in target but
// not in source), and record the keys common to both, in
// target's iteration order -- again a by-product of the
// source.find() call already needed to detect added keys. At
// the same time, determine whether every added key comes
// after every common key in target's order (a precondition
// for the fast path below, which only ever appends new keys
// at the very end): for an object_t whose iteration order is
// a pure function of the key set (e.g. the default std::map,
// which always iterates in sorted key order), the order
// check further below is always true and this whole
// mechanism is effectively a no-op; it only matters for a
// reorderable object_t such as the one backing `ordered_json`.
// patch ops for keys that were added (i.e., in target but not
// in source); built here so the fast path below can reuse
// them without a second source.find() per target key. Only
// used by the fast path -- the slow (reordering) path
// rebuilds "add" ops for every key itself.
std::vector<typename object_t::key_type> common_keys_target_order;
basic_json added_ops(value_t::array);
bool new_keys_form_suffix = true;
bool seen_new_key = false;
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
seen_new_key = true;
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
added_ops.push_back(
{
{"op", "add"}, {"path", path_key},
{"value", it.value()}
});
// recursive call to compare object values at key it
auto temp_diff = diff(it.value(), target[it.key()], path_key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
}
else
{
common_keys_target_order.push_back(it.key());
if (seen_new_key)
{
new_keys_form_suffix = false;
}
}
}
if (common_keys_source_order == common_keys_target_order && new_keys_form_suffix)
{
// fast path: order of common keys already matches (or the
// object_t's iteration order does not depend on
// insertion history), so a plain per-key recursive diff
// is correct and minimal, as before. common_keys_source_order
// is, by construction, the subsequence of source's keys
// that are common to both objects, in source's iteration
// order -- so it can be walked in lockstep with `source`
// using a cheap key comparison instead of another lookup.
// Deleted keys (those source keys not in common_keys_source_order)
// are interleaved here too, in source's original order, to
// match the historical (pre-reordering-aware) output order.
auto common_it = common_keys_source_order.cbegin();
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
auto temp_diff = diff(it.value(), target[it.key()], path_key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
++common_it;
}
else
{
// found a key that is not in target -> remove it
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
}
// append the "add" ops for brand-new keys collected above
// during the pass over target -- no second source.find()
// per target key needed
result.insert(result.end(), added_ops.begin(), added_ops.end());
}
else
{
// slow path: the common keys are in a different relative
// order in source and target (only possible for a
// reorderable object_t like ordered_map). Building a
// minimal reordering patch is a nontrivial (LCS-like)
// problem; instead, remove every source key -- both
// deleted keys (which must be removed regardless) and
// common keys (removed so they can be re-added in
// target's order) -- and re-add every key that should
// remain, with its final target value, in target's
// order. basic_json::patch()'s "add" operation on an
// object uses operator[], which appends at the end for a
// vector-backed insertion-ordered map when the key does
// not already exist -- so removing a key and then adding
// it moves it to the end, fixing its position.
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
// found a key that is not in o -> remove it
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
}
// add every key that is either common (just removed
// above) or brand new, in target's iteration order, so
// that the final order after applying the patch matches
// target exactly
for (auto it = target.cbegin(); it != target.cend(); ++it)
// second pass: traverse other object's elements
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
// found a key that is not in this -> add it
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(
{
-31
View File
@@ -273,36 +273,5 @@ TEST_CASE("Regression tests for extended diagnostics")
CHECK(j1["numbers"]["two"] == 2);
CHECK(j1["string"] == "t");
}
SECTION("Regression test - swap(array_t&)/swap(object_t&) must update JSON_DIAGNOSTICS parent pointers")
{
// swap(array_t&)
{
json j = json::array();
json::array_t arr = {json::array({1})};
j.swap(arr);
// parent pointers of the moved-in elements must point into j, not
// into the now-defunct free-standing array_t
CHECK_THROWS_WITH_AS(j[0][0].get<std::string>(), "[json.exception.type_error.302] (/0/0) type must be string, but is number", json::type_error);
// must not trigger assert_invariant() in a debug/assert-enabled build
json const k = j;
CHECK(k == j);
}
// swap(object_t&)
{
json o = json::object();
json::object_t obj = {{"a", json::array({1})}};
o.swap(obj);
CHECK_THROWS_WITH_AS(o["a"][0].get<std::string>(), "[json.exception.type_error.302] (/a/0) type must be string, but is number", json::type_error);
// must not trigger assert_invariant() in a debug/assert-enabled build
json const p = o;
CHECK(p == o);
}
}
}
-81
View File
@@ -81,84 +81,3 @@ TEST_CASE("regression test for issue #3732 - iteration_proxy_value<iter_impl<ord
};
static_cast<void>(fn);
}
TEST_CASE("regression test - diff() must account for ordered_json member order")
{
SECTION("pure reorder, no value changes")
{
ordered_json a = {{"a", 1}, {"b", 2}};
ordered_json b = {{"b", 2}, {"a", 1}};
CHECK(a != b); // order-sensitive equality
CHECK(a.patch(ordered_json::diff(a, b)) == b);
}
SECTION("new key must land at the front")
{
ordered_json c = {{"b", 2}};
ordered_json e = {{"a", 1}, {"b", 2}};
CHECK(c.patch(ordered_json::diff(c, e)) == e);
}
SECTION("reorder plus a value change on one of the reordered keys")
{
ordered_json a = {{"a", 1}, {"b", 2}};
ordered_json b = {{"b", 20}, {"a", 1}};
CHECK(a != b);
CHECK(a.patch(ordered_json::diff(a, b)) == b);
}
SECTION("reorder plus a deleted key")
{
ordered_json a = {{"a", 1}, {"b", 2}, {"c", 3}};
ordered_json b = {{"b", 2}, {"a", 1}};
CHECK(a != b);
CHECK(a.patch(ordered_json::diff(a, b)) == b);
}
SECTION("reorder plus a nested value that itself needs a recursive diff")
{
ordered_json a = {{"a", {{"x", 1}, {"y", 2}}}, {"b", 2}};
ordered_json b = {{"b", 2}, {"a", {{"x", 1}, {"y", 99}}}};
CHECK(a != b);
CHECK(a.patch(ordered_json::diff(a, b)) == b);
}
SECTION("three or more keys shuffled into a different order")
{
ordered_json a = {{"a", 1}, {"b", 2}, {"c", 3}, {"d", 4}};
ordered_json b = {{"d", 4}, {"b", 2}, {"a", 1}, {"c", 3}};
CHECK(a != b);
CHECK(a.patch(ordered_json::diff(a, b)) == b);
}
SECTION("matching order still produces a minimal patch (fast path unaffected)")
{
ordered_json a = {{"a", 1}, {"b", 2}, {"c", 3}};
ordered_json b = {{"a", 1}, {"b", 20}, {"c", 3}};
auto p = ordered_json::diff(a, b);
// only the changed value should be touched, not a wholesale remove+add
CHECK(p.size() == 1);
CHECK(p[0]["op"] == "replace");
CHECK(p[0]["path"] == "/b");
CHECK(a.patch(p) == b);
}
SECTION("plain json (std::map-backed) is unaffected by same-key-different-insertion-order")
{
json a;
a["b"] = 2;
a["a"] = 1;
json b;
b["a"] = 1;
b["b"] = 2;
// std::map iteration is always sorted by key, so a == b regardless of
// insertion order, and diff() must still produce the same minimal
// (empty) result as before this fix
CHECK(a == b);
auto p = json::diff(a, b);
CHECK(p.empty());
CHECK(a.patch(p) == b);
}
}
+2 -2
View File
@@ -304,8 +304,8 @@ TEST_CASE("Unicode (3/5)" * doctest::skip())
{
for (int byte4 = 0x00; byte4 <= 0xFF; ++byte4)
{
// skip fourth second byte
if (0x80 <= byte3 && byte3 <= 0xBF)
// skip correct fourth byte
if (0x80 <= byte4 && byte4 <= 0xBF)
{
continue;
}
+1 -1
View File
@@ -305,7 +305,7 @@ TEST_CASE("Unicode (4/5)" * doctest::skip())
for (int byte4 = 0x00; byte4 <= 0xFF; ++byte4)
{
// skip correct fourth byte
if (0x80 <= byte3 && byte3 <= 0xBF)
if (0x80 <= byte4 && byte4 <= 0xBF)
{
continue;
}
+1 -1
View File
@@ -305,7 +305,7 @@ TEST_CASE("Unicode (5/5)" * doctest::skip())
for (int byte4 = 0x00; byte4 <= 0xFF; ++byte4)
{
// skip correct fourth byte
if (0x80 <= byte3 && byte3 <= 0xBF)
if (0x80 <= byte4 && byte4 <= 0xBF)
{
continue;
}