compiler warning: asn1tostruct.py: return 0 at end of *_free_*()

Part of the resulting diff in the generated code:

--- /tmp/hnbap_decoder.c	2017-12-24 17:06:50.983979866 +0100
+++ /tmp/hnbap_decoder.c	2017-12-24 17:07:10.760223354 +0100
@@ -1179,6 +1179,7 @@
     TNLUpdateResponseIEs_t *tnlUpdateResponseIEs) {

     ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_Context_ID, &tnlUpdateResponseIEs->context_ID);
+    return 0;
 }

 int hnbap_free_tnlupdaterequesties(
@@ -1187,6 +1188,7 @@
     ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_Context_ID, &tnlUpdateRequestIEs->context_ID);
     ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_RABList, &tnlUpdateRequestIEs->rabList);
     ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_Update_cause, &tnlUpdateRequestIEs->update_cause);
+    return 0;
 }

 int hnbap_free_errorindicationies(
@@ -1197,12 +1199,14 @@
     if ((errorIndicationIEs->presenceMask & ERRORINDICATIONIES_CRITICALITYDIAGNOSTICS_PRESENT)
         == ERRORINDICATIONIES_CRITICALITYDIAGNOSTICS_PRESENT)
         ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_CriticalityDiagnostics, &errorIndicationIEs->criticalityDiagnostics);
+    return 0;
 }

 int hnbap_free_hnbconfigtransferrequesties(
     HNBConfigTransferRequestIEs_t *hnbConfigTransferRequestIEs) {

     ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_NeighbourInfoRequestList, &hnbConfigTransferRequestIEs->neighbourInfoRequestList);
+    return 0;
 }

 int hnbap_free_tnlupdatefailureies(

[etc.]

Related: OS#2670
Change-Id: Ieba12c09c33a81da964bf88a858714d922ced8c0

asn1/utils/asn1tostruct.py

@@ -389,6 +389,8 @@ for key in iesDefs:
         iename = re.sub('id-', '', ie[0])
         ienameunderscore = lowerFirstCamelWord(re.sub('-', '_', iename))
         f.write("    ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_%s, &%s->%s);\n" % (ietypeunderscore, lowerFirstCamelWord(re.sub('-', '_', key)), ienameunderscore))
+
+    f.write("    return 0;\n")
     f.write("}\n\n")
 
 for key in iesDefs: