support use of decode/encode/transcode for varnish >= 5.0

We _could_ selectively keep the tests for these functions failing in <5.0,
but looking forward this does seem like wasted effort.

src/tests/usage.vtc

@@ -4,53 +4,13 @@ varnishtest "test permitted use of functions in vcl_subs"
 
 varnish v1 -vcl { backend b { .host="${bad_ip}"; } } -start
 
-varnish v1 -errvcl {vmod blobcode error: decode() is illegal in vcl_init() and vcl_fini().vmod blobcode error: encode() is illegal in vcl_init() and vcl_fini().} {
-	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
-	backend b { .host="${bad_ip}"; }
-	sub vcl_init {
-	  new err = blobcode.blob(IDENTITY, blobcode.encode(IDENTITY,
-				  blobcode.decode(IDENTITY, "x")));
-	}
-}
-
-varnish v1 -errvcl {vmod blobcode error: transcode() is illegal in vcl_init() and vcl_fini().} {
-	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
-	backend b { .host="${bad_ip}"; }
-	sub vcl_init {
-	  new err = blobcode.blob(IDENTITY,
-				  blobcode.transcode(IDENTITY, IDENTITY, "x"));
-	}
-}
-
-varnish v1 -errvcl {vmod blobcode error: encode() is illegal in vcl_init() and vcl_fini().} {
-	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
-	backend b { .host="${bad_ip}"; }
-	sub vcl_init {
-	  new b1 = blobcode.blob(IDENTITY, "foo");
-	  new b2 = blobcode.blob(IDENTITY, blobcode.encode(IDENTITY, b1.get()));
-	}
-}
-
-varnish v1 -errvcl {vmod blobcode error: decode() is illegal in vcl_init() and vcl_fini().vmod blobcode error: encode() is illegal in vcl_init() and vcl_fini().} {
-	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
-	backend b { .host="${bad_ip}"; }
-	sub vcl_init {
-	  new err = blobcode.blob(IDENTITY, blobcode.encode(IDENTITY,
-				  blobcode.decode_n(1, IDENTITY, "x")));
-	}
-}
-
-varnish v1 -errvcl {vmod blobcode error: transcode() is illegal in vcl_init() and vcl_fini().} {
-	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
-	backend b { .host="${bad_ip}"; }
-	sub vcl_init {
-	  new err = blobcode.blob(IDENTITY,
-				  blobcode.transcode_n(1, IDENTITY, IDENTITY,
-						       "x"));
-	}
-}
+# for varnish < 5.0, we have no workspace in init/fini, so we cannot
+# use the *code() functions there
+# We could have separate tests for those versions, but looking forward,
+# this appears to be wasted effort.
+# The *code() functions are legal in every other VCL sub for all supported
+# varnish versions
 
-# The *code() functions are legal in every other VCL sub
 varnish v1 -vcl {
 	import blobcode from "${vmod_topbuild}/src/.libs/libvmod_blobcode.so";
 	backend b { .host="${bad_ip}"; }

src/vmod_blobcode.c

@@ -136,9 +136,6 @@ static const struct vmod_blobcode_fptr {
 
 #define INIT_FINI(ctx) (((ctx)->method & (VCL_MET_INIT | VCL_MET_FINI)) != 0)
 
-#define ILLEGAL(ctx, m) \
-	ERR((ctx), m " is illegal in vcl_init() and vcl_fini().")
-
 static const struct vmod_priv null_blob[1] =
 {
 	{
@@ -398,6 +395,17 @@ decode_id_inplace(struct vmod_priv *b, VCL_INT n, const char *restrict p,
 	return (b);
 }
 
+static int
+has_ws(VRT_CTX, const char * const msg)
+{
+	if (VRT_MAJOR_VERSION < 5 && INIT_FINI(ctx)) {
+		VERR(ctx, "%s", msg);
+		return 0;
+	}
+
+	return 1;
+}
+
 static VCL_BLOB
 decode(VRT_CTX, VCL_INT n, VCL_ENUM decs,
        const char *restrict const p, va_list ap) {
@@ -410,10 +418,9 @@ decode(VRT_CTX, VCL_INT n, VCL_ENUM decs,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	AENC(dec);
 
-	if (INIT_FINI(ctx)) {
-		ILLEGAL(ctx, "decode()");
+	if (! has_ws(ctx, __func__))
 		return NULL;
-	}
+
 	CHECK_OBJ_NOTNULL(ctx->ws, WS_MAGIC);
 
 	snap = WS_Snapshot(ctx->ws);
@@ -494,14 +501,14 @@ encode(VRT_CTX, enum encoding enc, VCL_BLOB b) {
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	AENC(enc);
 
-	if (INIT_FINI(ctx)) {
-		ILLEGAL(ctx, "encode()");
+	if (! has_ws(ctx, __func__))
 		return NULL;
-	}
+
+	CHECK_OBJ_NOTNULL(ctx->ws, WS_MAGIC);
+
 	if (b == NULL)
 		return NULL;
 
-	CHECK_OBJ_NOTNULL(ctx->ws, WS_MAGIC);
 	if (wb_create(ctx->ws, &wb) == NULL) {
 		ERRNOMEM(ctx, "cannot encode");
 		return NULL;
@@ -539,10 +546,10 @@ transcode(VRT_CTX, VCL_INT n, VCL_ENUM decs, VCL_ENUM encs,
 	VCL_STRING r;
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
-	if (INIT_FINI(ctx)) {
-		ILLEGAL(ctx, "transcode()");
+
+	if (! has_ws(ctx, __func__))
 		return NULL;
-	}
+
 	CHECK_OBJ_NOTNULL(ctx->ws, WS_MAGIC);
 
 	AENC(dec);

src/vmod_blobcode.vcc

@@ -338,10 +338,11 @@ string is an illegal format for the decoding scheme.
 If the ``blob`` object constructor fails, then the VCL program will
 fail to load, and the VCC compiler will emit an error message.
 
-The VMOD functions -- ``encode()``, ``decode()`` and ``transcode()``
--- may not be called in ``vcl_init()`` or ``vcl_fini()`` (since a
-workspace must be available). Use in ``vcl_init()`` will also cause
-the VCL program to fail with a VCC compiler error.
+For varnish versions before 5.0, the VMOD functions -- ``encode()``,
+``decode()`` and ``transcode()`` -- may not be called in
+``vcl_init()`` or ``vcl_fini()`` (since a workspace must be
+available). Use in ``vcl_init()`` will also cause the VCL program to
+fail with a VCC compiler error.
 
 If any of the VMOD's methods or functions fail at runtime, then an
 error message will be written to the Varnish log using the tag