Fixed a crash

CHANGES_NEXT_RELEASE

@@ -1,2 +1,3 @@
 Fixed Issues:
-* Issue #1227  Case insensitive matching for http request header keys
+* Issue #280  Crash when an attributed is PATCHed to have an empty array as value
+

src/lib/orionld/serviceRoutines/orionldPatchEntity2.cpp

@@ -325,6 +325,13 @@ bool kjValuesDiffer(KjNode* leftAttr, KjNode* rightAttr)
   if (type == KjBoolean)  return (left->value.b == right->value.b)?            false : true;
 
   // Compound values ... let's just render the values and do a strcmp on the rendered buffers
+  // However, might be an empty array/object  (kjFastRenderSize crashes if the parameter is NULL)
+  //
+  if ((left->value.firstChildP == NULL) && (right->value.firstChildP == NULL))
+    return false;
+  else if ((left->value.firstChildP == NULL) || (right->value.firstChildP == NULL))
+    return true;
+
   int   leftBufSize     = kjFastRenderSize(left->value.firstChildP);
   int   rightBufSize    = kjFastRenderSize(right->value.firstChildP);
   char* leftBuf         = kaAlloc(&orionldState.kalloc, leftBufSize);

test/functionalTest/cases/0000_ngsild/ngsild_patch_entity2-attr-with-empty-array-as-value.test

@@ -0,0 +1,156 @@
+# Copyright 2022 FIWARE Foundation e.V.
+#
+# This file is part of Orion-LD Context Broker.
+#
+# Orion-LD Context Broker is free software: you can redistribute it and/or
+# modify it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# Orion-LD Context Broker is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero
+# General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with Orion-LD Context Broker. If not, see http://www.gnu.org/licenses/.
+#
+# For those usages not covered by this license please contact with
+# orionld at fiware dot org
+
+# VALGRIND_READY - to mark the test ready for valgrindTestSuite.sh
+
+--NAME--
+Update an entity attribute using PATCH
+
+--SHELL-INIT--
+export BROKER=orionld
+dbInit CB
+brokerStart CB 0 IPv4 -experimental
+
+--SHELL--
+#
+# 01. Create an entity E1 with an attribute P1=[]
+# 02. Patch E1, setting P1=[] - make sure there's no crash
+# 03. GET E1
+# 04. Patch E1, setting P1=[] - again
+# 05. GET E1
+#
+
+echo "01. Create an entity E1 with an attribute P1=1"
+echo "=============================================="
+payload='{
+  "id": "urn:E1",
+  "type": "T",
+  "@context": [ "https://fiware.github.io/NGSI-LD_TestSuite/ldContext/testContext.jsonld" ]
+}'
+orionCurl --url /ngsi-ld/v1/entities --payload "$payload" -H "Content-Type: application/ld+json"
+echo
+echo
+
+
+echo "02. Patch E1, setting P1=[] - make sure there's no crash"
+echo "========================================================"
+payload='{
+  "@context": [ "https://fiware.github.io/NGSI-LD_TestSuite/ldContext/testContext.jsonld" ],
+  "P1": {
+    "type": "Property",
+    "value": []
+  }
+}'
+orionCurl --url /ngsi-ld/v1/entities/urn:E1 -X PATCH --payload "$payload" -H "Content-Type: application/ld+json"
+echo
+echo
+
+
+echo "03. GET E1"
+echo "=========="
+orionCurl --url /ngsi-ld/v1/entities/urn:E1
+echo
+echo
+
+
+echo "04. Patch E1, setting P1=[] - again"
+echo "==================================="
+payload='{
+  "@context": [ "https://fiware.github.io/NGSI-LD_TestSuite/ldContext/testContext.jsonld" ],
+  "P1": {
+    "type": "Property",
+    "value": []
+  }
+}'
+orionCurl --url /ngsi-ld/v1/entities/urn:E1 -X PATCH --payload "$payload" -H "Content-Type: application/ld+json"
+echo
+echo
+
+
+echo "05. GET E1"
+echo "=========="
+orionCurl --url /ngsi-ld/v1/entities/urn:E1
+echo
+echo
+
+
+--REGEXPECT--
+01. Create an entity E1 with an attribute P1=1
+==============================================
+HTTP/1.1 201 Created
+Content-Length: 0
+Date: REGEX(.*)
+Location: /ngsi-ld/v1/entities/urn:E1
+
+
+
+02. Patch E1, setting P1=[] - make sure there's no crash
+========================================================
+HTTP/1.1 204 No Content
+Date: REGEX(.*)
+
+
+
+03. GET E1
+==========
+HTTP/1.1 200 OK
+Content-Length: 100
+Content-Type: application/json
+Date: REGEX(.*)
+Link: <https://uri.etsi.org/ngsi-ld/v1/ngsi-ld-core-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json"
+
+{
+    "http://example.org/P1": {
+        "type": "Property",
+        "value": []
+    },
+    "id": "urn:E1",
+    "type": "http://example.org/T"
+}
+
+
+04. Patch E1, setting P1=[] - again
+===================================
+HTTP/1.1 204 No Content
+Date: REGEX(.*)
+
+
+
+05. GET E1
+==========
+HTTP/1.1 200 OK
+Content-Length: 100
+Content-Type: application/json
+Date: REGEX(.*)
+Link: <https://uri.etsi.org/ngsi-ld/v1/ngsi-ld-core-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json"
+
+{
+    "http://example.org/P1": {
+        "type": "Property",
+        "value": []
+    },
+    "id": "urn:E1",
+    "type": "http://example.org/T"
+}
+
+
+--TEARDOWN--
+brokerStop CB
+dbDrop CB