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authorArseny Kapoulkine <arseny.kapoulkine@gmail.com>2017-11-13 08:57:16 -0800
committerArseny Kapoulkine <arseny.kapoulkine@gmail.com>2017-11-13 08:57:16 -0800
commit4bd8771c2fffe6d81ae053e9570b0b53033b0c82 (patch)
tree6fd09edcfb164460aafc8b8809e4858f35b3f2af
parent91a3c28862a5a96b08a81c38539dba0bc41bb1ee (diff)
Implement correct move error handling for compact mode
In compact mode, we currently can not support zero-allocation moves since some pointer assignments required during the move need to allocate hash table slots. This is mostly applicable to xml_document_struct::first_child, since the pointer to this element is used as a hash table key, but there are some contrived cases where parents of root's children need a hash slot and didn't have it before. These cases can be fixed by changing the compact encoding to be a bit more move friendly, but for now it's easier to handle the error and throw/return during move. When this happens, the source document doesn't change.
-rw-r--r--src/pugixml.cpp32
1 files changed, 27 insertions, 5 deletions
diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 8f83619..f6a5654 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -6954,6 +6954,33 @@ namespace pugi
impl::xml_document_struct* doc = static_cast<impl::xml_document_struct*>(_root);
impl::xml_document_struct* other = static_cast<impl::xml_document_struct*>(rhs._root);
+ // save first child pointer for later; this needs hash access
+ xml_node_struct* other_first_child = other->first_child;
+
+ #ifdef PUGIXML_COMPACT
+ // reserve space for the hash table up front; this is the only operation that can fail
+ // if it does, we have no choice but to throw (if we have exceptions)
+ if (other_first_child)
+ {
+ size_t other_children = 0;
+ for (xml_node_struct* child = other_first_child; child; child = child->next_sibling)
+ other_children++;
+
+ // in compact mode, each pointer assignment could result in a hash table request
+ // during move, we have to relocate document first_child and parents of all children
+ // normally there's just one child and its parent has a pointerless encoding but
+ // we assume the worst here
+ if (!other->_hash->reserve(other_children + 1))
+ {
+ #ifdef PUGIXML_NO_EXCEPTIONS
+ return;
+ #else
+ throw std::bad_alloc();
+ #endif
+ }
+ }
+ #endif
+
// move allocation state
doc->_root = other->_root;
doc->_busy_size = other->_busy_size;
@@ -6963,9 +6990,6 @@ namespace pugi
doc->extra_buffers = other->extra_buffers;
_buffer = rhs._buffer;
- // save first child pointer for later; this needs hash access
- xml_node_struct* other_first_child = other->first_child;
-
#ifdef PUGIXML_COMPACT
// move compact hash; note that the hash table can have pointers to other but they will be "inactive", similarly to nodes removed with remove_child
doc->hash = other->hash;
@@ -7010,7 +7034,6 @@ namespace pugi
// move tree structure
assert(!doc->first_child);
- doc->reserve(); // TODO: it's not clear how to handle reserve running out of memory
doc->first_child = other_first_child;
for (xml_node_struct* node = other_first_child; node; node = node->next_sibling)
@@ -7019,7 +7042,6 @@ namespace pugi
// most children will have migrated when we reassigned compact_shared_parent
assert(node->parent == other || node->parent == doc);
- doc->reserve(); // TODO: it's not clear how to handle reserve running out of memory
node->parent = doc;
#else
assert(node->parent == other);