extensibility fix, at least

tests/126-per-extensions-OK.asn1

+
+-- OK: Everything is fine
+
+-- iso.org.dod.internet.private.enterprise (1.3.6.1.4.1)
+-- .spelio.software.asn1c.test (9363.1.5.1)
+-- .126
+
+ModulePERExtensions
+	{ iso org(3) dod(6) internet (1) private(4) enterprise(1)
+		spelio(9363) software(1) asn1c(5) test(1) 126 }
+	DEFINITIONS AUTOMATIC TAGS ::=
+BEGIN
+
+	PDU ::= SEQUENCE {
+		...,
+		str-o	IA5String	OPTIONAL,
+		str-m	IA5String
+	}
+
+END

tests/126-per-extensions-OK.asn1.-Pgen-PER

+
+/*** <<< INCLUDES [PDU] >>> ***/
+
+#include <IA5String.h>
+#include <constr_SEQUENCE.h>
+
+/*** <<< TYPE-DECLS [PDU] >>> ***/
+
+typedef struct PDU {
+	/*
+	 * This type is extensible,
+	 * possible extensions are below.
+	 */
+	IA5String_t	*str_o	/* OPTIONAL */;
+	IA5String_t	*str_m;
+	
+	/* Context for parsing across buffer boundaries */
+	asn_struct_ctx_t _asn_ctx;
+} PDU_t;
+
+/*** <<< FUNC-DECLS [PDU] >>> ***/
+
+extern asn_TYPE_descriptor_t asn_DEF_PDU;
+
+/*** <<< STAT-DEFS [PDU] >>> ***/
+
+static asn_TYPE_member_t asn_MBR_PDU_1[] = {
+	{ ATF_POINTER, 2, offsetof(struct PDU, str_o),
+		.tag = (ASN_TAG_CLASS_CONTEXT | (0 << 2)),
+		.tag_mode = -1,	/* IMPLICIT tag at current level */
+		.type = &asn_DEF_IA5String,
+		.memb_constraints = 0,	/* Defer constraints checking to the member type */
+		.per_constraints = 0,	/* No PER visible constraints */
+		.default_value = 0,
+		.name = "str-o"
+		},
+	{ ATF_POINTER, 1, offsetof(struct PDU, str_m),
+		.tag = (ASN_TAG_CLASS_CONTEXT | (1 << 2)),
+		.tag_mode = -1,	/* IMPLICIT tag at current level */
+		.type = &asn_DEF_IA5String,
+		.memb_constraints = 0,	/* Defer constraints checking to the member type */
+		.per_constraints = 0,	/* No PER visible constraints */
+		.default_value = 0,
+		.name = "str-m"
+		},
+};
+static int asn_MAP_PDU_oms_1[] = { 0, 1 };
+static ber_tlv_tag_t asn_DEF_PDU_tags_1[] = {
+	(ASN_TAG_CLASS_UNIVERSAL | (16 << 2))
+};
+static asn_TYPE_tag2member_t asn_MAP_PDU_tag2el_1[] = {
+    { (ASN_TAG_CLASS_CONTEXT | (0 << 2)), 0, 0, 0 }, /* str-o at 16 */
+    { (ASN_TAG_CLASS_CONTEXT | (1 << 2)), 1, 0, 0 } /* str-m at 17 */
+};
+static asn_SEQUENCE_specifics_t asn_SPC_PDU_specs_1 = {
+	sizeof(struct PDU),
+	offsetof(struct PDU, _asn_ctx),
+	asn_MAP_PDU_tag2el_1,
+	2,	/* Count of tags in the map */
+	asn_MAP_PDU_oms_1,	/* Optional members */
+	0, 2,	/* Root/Additions */
+	-1,	/* Start extensions */
+	3	/* Stop extensions */
+};
+asn_TYPE_descriptor_t asn_DEF_PDU = {
+	"PDU",
+	"PDU",
+	SEQUENCE_free,
+	SEQUENCE_print,
+	SEQUENCE_constraint,
+	SEQUENCE_decode_ber,
+	SEQUENCE_encode_der,
+	SEQUENCE_decode_xer,
+	SEQUENCE_encode_xer,
+	SEQUENCE_decode_uper,
+	SEQUENCE_encode_uper,
+	0,	/* Use generic outmost tag fetcher */
+	asn_DEF_PDU_tags_1,
+	sizeof(asn_DEF_PDU_tags_1)
+		/sizeof(asn_DEF_PDU_tags_1[0]), /* 1 */
+	asn_DEF_PDU_tags_1,	/* Same as above */
+	sizeof(asn_DEF_PDU_tags_1)
+		/sizeof(asn_DEF_PDU_tags_1[0]), /* 1 */
+	0,	/* No PER visible constraints */
+	asn_MBR_PDU_1,
+	2,	/* Elements count */
+	&asn_SPC_PDU_specs_1	/* Additional specs */
+};
+