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Add leave_container() to match enter_container()

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Every container is opened through enter_container(), whose docs
promise that a check placed there runs before every start event. The
close side had no equivalent: the same
"container_stack.pop_back(); dispatch to end_object() or end_array()"
sequence was written out separately in BSON, CBOR, MessagePack,
UBJSON/BJData and BON8, each copying the pattern of keeping an
is_object flag around the pop_back() that would otherwise invalidate
a reference to it. A check needed on close would have had to be added
in five places, and a sixth copy could go unnoticed.

Add leave_container() next to enter_container(), doing the same
pop-then-dispatch, and replace the five sites with it. Each site keeps
its own surrounding logic (BSON's check_bson_document_size() call
before popping, MessagePack's is_object copy used again below,
UBJSON/BJData's remaining-container handling after popping, BON8's
top used again below); only the repeated pop/dispatch line pair is
now shared.

Verified all six binary-format unit suites and unit-regression2's
deep-nesting tests (dependent count/reuse count and the bjdata ndarray
depth cases) still pass, compiled with -Wall -Wextra and ASan/UBSan.

Overlaps #5601, which is expected to add a sixth close site in its own
skip loop; that site can route through leave_container() too once it
lands.

#5711 item 4

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-30 18:45:25 +02:00
parent 391bc271b2
commit a8b078ea37
2 changed files with 46 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/input/binary_reader.hpp
+23 -12
View File
@@ -270,6 +270,22 @@ class binary_reader
return enter_container(/*is_object*/true, len, type_marker);
}
/*!
@brief close the innermost open array or object
Pops the container opened by the matching @ref enter_container call and
emits the SAX end event. Every format-specific driver otherwise repeated
the same pop-then-dispatch sequence at its own close site.
@return whether the SAX parser accepted the end event
*/
bool leave_container()
{
const bool is_object = container_stack.back().is_object;
container_stack.pop_back();
return is_object ? sax->end_object() : sax->end_array();
}
//////////
// BSON //
//////////
@@ -354,8 +370,8 @@ class binary_reader
if (element_type == 0) // end of the innermost document
{
// a copy, not a reference: it must stay valid across the
// pop_back() below, which destroys the container_stack
// element it would otherwise alias
// pop_back() inside leave_container() below, which destroys
// the container_stack element it would otherwise alias
const container_frame top = container_stack.back();
if (JSON_HEDLEY_UNLIKELY(!check_bson_document_size(top.start_position, top.declared_size)))
@@ -363,8 +379,7 @@ class binary_reader
return false;
}
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -1549,8 +1564,7 @@ class binary_reader
if (at_end)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -2297,8 +2311,7 @@ class binary_reader
if (container_stack.back().remaining == 0)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -2427,8 +2440,7 @@ class binary_reader
break;
}
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -3413,8 +3425,7 @@ class binary_reader
if (at_end)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
single_include/nlohmann/json.hpp
+23 -12
View File
@@ -13030,6 +13030,22 @@ class binary_reader
return enter_container(/*is_object*/true, len, type_marker);
}
/*!
@brief close the innermost open array or object
Pops the container opened by the matching @ref enter_container call and
emits the SAX end event. Every format-specific driver otherwise repeated
the same pop-then-dispatch sequence at its own close site.
@return whether the SAX parser accepted the end event
*/
bool leave_container()
{
const bool is_object = container_stack.back().is_object;
container_stack.pop_back();
return is_object ? sax->end_object() : sax->end_array();
}
//////////
// BSON //
//////////
@@ -13114,8 +13130,8 @@ class binary_reader
if (element_type == 0) // end of the innermost document
{
// a copy, not a reference: it must stay valid across the
// pop_back() below, which destroys the container_stack
// element it would otherwise alias
// pop_back() inside leave_container() below, which destroys
// the container_stack element it would otherwise alias
const container_frame top = container_stack.back();
if (JSON_HEDLEY_UNLIKELY(!check_bson_document_size(top.start_position, top.declared_size)))
@@ -13123,8 +13139,7 @@ class binary_reader
return false;
}
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -14309,8 +14324,7 @@ class binary_reader
if (at_end)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -15057,8 +15071,7 @@ class binary_reader
if (container_stack.back().remaining == 0)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -15187,8 +15200,7 @@ class binary_reader
break;
}
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}
@@ -16173,8 +16185,7 @@ class binary_reader
if (at_end)
{
container_stack.pop_back();
if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
if (JSON_HEDLEY_UNLIKELY(!leave_container()))
{
return false;
}