Add some checks, and clarify what happens when blob->priv is NULL.

README.rst

@@ -65,6 +65,10 @@ same
 Returns true if and only if the two BLOB arguments are the same
 object, i.e. they specify exactly the same region of memory.
 
+If the BLOBs are both empty (length is 0 and/or the internal pointer
+is NULL), then ``same()`` returns ``true``. If any non-empty BLOB
+is compared to an empty BLOB, then ``same()`` returns ``false``.
+
 .. _func_equal:
 
 equal
@@ -77,6 +81,10 @@ equal
 Returns true if and only if the two BLOB arguments have equal contents
 (possibly in different memory regions).
 
+As with ``same()``: If the BLOBs are both empty, then ``equal()``
+returns ``true``. If any non-empty BLOB is compared to an empty BLOB,
+then ``equal()`` returns ``false``.
+
 .. _func_length:
 
 length
@@ -110,10 +118,10 @@ The value of the returned integer results from the bytes from the BLOB
 in ascending order of addresses interpreted according to the
 endianness of the system on which Varnish is running.
 
-If the length of the BLOB is 0, then ``integer()`` returns 0 and emits
-an error message to the Varnish log using the ``VCL_Error`` tag. If
-this happens when ``integer()`` is called in ``vcl_init``, then the
-VCL load fails with the error message. If it happens in any other VCL
+If the BLOB is empty, then ``integer()`` returns 0 and emits an error
+message to the Varnish log using the ``VCL_Error`` tag. If this
+happens when ``integer()`` is called in ``vcl_init``, then the VCL
+load fails with the error message. If it happens in any other VCL
 subroutine, then VCL processing continues. Since 0 can be a legitimate
 return value, you should monitor the Varnish log for the error.
 

src/tests/01blob.vtc

@@ -271,12 +271,12 @@ client c1 {
 
 logexpect l1 -v v1 -d 1 -g vxid -q "VCL_Error" {
 	expect 0 * Begin req
-	expect * = VCL_Error "^vmod blob error: blob length is 0 in blob.integer..$"
+	expect * = VCL_Error "^vmod blob error: blob is empty in blob.integer..$"
 	expect * = End
 } -run
 
 # VCL load fails if integer() is called for an empty blob in vcl_init
-varnish v1 -errvcl {vmod blob error: blob length is 0 in blob.integer()} {
+varnish v1 -errvcl {vmod blob error: blob is empty in blob.integer()} {
 	import blob from "${vmod_topbuild}/src/.libs/libvmod_blob.so";
 	import blobcode;
 	backend b { .host = "${bad_ip}"; }

src/vmod_blob.c

@@ -68,22 +68,30 @@ errmsg(VRT_CTX, const char *fmt, ...)
 VCL_BOOL
 vmod_same(VRT_CTX __attribute__((unused)), VCL_BLOB b1, VCL_BLOB b2)
 {
+	AN(b1);
+	AN(b2);
 	return b1->len == b2->len && b1->priv == b2->priv;
 }
 
 VCL_BOOL
 vmod_equal(VRT_CTX __attribute__((unused)), VCL_BLOB b1, VCL_BLOB b2)
 {
+	AN(b1);
+	AN(b2);
+
 	if (b1->len != b2->len)
 		return 0;
 	if (b1->priv == b2->priv)
 		return 1;
+	if (b1->priv == NULL || b2->priv == NULL)
+		return 0;
 	return (memcmp(b1->priv, b2->priv, b1->len) == 0);
 }
 
 VCL_INT
 vmod_length(VRT_CTX __attribute__((unused)), VCL_BLOB b)
 {
+	AN(b);
 	return b->len;
 }
 
@@ -92,13 +100,17 @@ vmod_integer(VRT_CTX, VCL_BLOB b, VCL_ENUM padding)
 {
 	VCL_INT i = 0;
 
+	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
+	AN(b);
 	assert(b->len >= 0);
-	if ((unsigned)b->len >= sizeof(VCL_INT))
-		return *((VCL_INT *) b->priv);
-	if (b->len == 0) {
-		ERR(ctx, "blob length is 0 in blob.integer()");
+
+	if (b->len == 0 || b->priv == NULL) {
+		ERR(ctx, "blob is empty in blob.integer()");
 		return 0;
 	}
+
+	if ((unsigned)b->len >= sizeof(VCL_INT))
+		return *((VCL_INT *) b->priv);
 	for (int j = 0; j < b->len; j++)
 		i |= ((unsigned char *)b->priv)[j] << ((b->len - j - 1) * 8);
 	if (padding[0] == 'R')

src/vmod_blob.vcc

@@ -34,11 +34,19 @@ $Function BOOL same(BLOB, BLOB)
 Returns true if and only if the two BLOB arguments are the same
 object, i.e. they specify exactly the same region of memory.
 
+If the BLOBs are both empty (length is 0 and/or the internal pointer
+is NULL), then ``same()`` returns ``true``. If any non-empty BLOB
+is compared to an empty BLOB, then ``same()`` returns ``false``.
+
 $Function BOOL equal(BLOB, BLOB)
 
 Returns true if and only if the two BLOB arguments have equal contents
 (possibly in different memory regions).
 
+As with ``same()``: If the BLOBs are both empty, then ``equal()``
+returns ``true``. If any non-empty BLOB is compared to an empty BLOB,
+then ``equal()`` returns ``false``.
+
 $Function INT length(BLOB)
 
 Returns the length of the BLOB.
@@ -58,10 +66,10 @@ The value of the returned integer results from the bytes from the BLOB
 in ascending order of addresses interpreted according to the
 endianness of the system on which Varnish is running.
 
-If the length of the BLOB is 0, then ``integer()`` returns 0 and emits
-an error message to the Varnish log using the ``VCL_Error`` tag. If
-this happens when ``integer()`` is called in ``vcl_init``, then the
-VCL load fails with the error message. If it happens in any other VCL
+If the BLOB is empty, then ``integer()`` returns 0 and emits an error
+message to the Varnish log using the ``VCL_Error`` tag. If this
+happens when ``integer()`` is called in ``vcl_init``, then the VCL
+load fails with the error message. If it happens in any other VCL
 subroutine, then VCL processing continues. Since 0 can be a legitimate
 return value, you should monitor the Varnish log for the error.