Fix undefined behavior while calling memcpy

Calling memcpy(x, 0, 0) is technically undefined (although it should usually
be a no-op).

2 files changed, 18 insertions, 1 deletions

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 4b1d5ab..59e8f79 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -1352,7 +1352,11 @@ PUGI__NS_BEGIN
 			char_t* buffer = static_cast<char_t*>(xml_memory::allocate((length + 1) * sizeof(char_t)));
 			if (!buffer) return false;
 
-			memcpy(buffer, contents, length * sizeof(char_t));
+			if (contents)
+				memcpy(buffer, contents, length * sizeof(char_t));
+			else
+				assert(length == 0);
+
 			buffer[length] = 0;
 
 			out_buffer = buffer;
diff --git a/tests/test_dom_modify.cpp b/tests/test_dom_modify.cpp
index 07fe6dc..45cf3ea 100644
--- a/tests/test_dom_modify.cpp
+++ b/tests/test_dom_modify.cpp
@@ -1091,6 +1091,19 @@ TEST_XML(dom_node_append_buffer_fragment, "<node />")
 	CHECK_NODE(doc, STR("<node>1234</node>"));
 }
 
+TEST_XML(dom_node_append_buffer_empty, "<node />")
+{
+	xml_node node = doc.child(STR("node"));
+
+	CHECK(node.append_buffer("", 0).status == status_no_document_element);
+	CHECK(node.append_buffer("", 0, parse_fragment).status == status_ok);
+
+	CHECK(node.append_buffer(0, 0).status == status_no_document_element);
+	CHECK(node.append_buffer(0, 0, parse_fragment).status == status_ok);
+
+	CHECK_NODE(doc, STR("<node />"));
+}
+
 TEST_XML(dom_node_prepend_move, "<node>foo<child/></node>")
 {
 	xml_node child = doc.child(STR("node")).child(STR("child"));