TAKE_OBJ_NOTNULLification: cases with the first AN(objp) missing

in these cases, the initial AN(objp) was missing, so we would
potentially dereference a NULL pointer without an explicit assertion
failure.

in VCL_Rel(), AN(*vcc) was likely just a typo resulting in a semantic
noop (the check was a duplication of the NULL check in
CHECK_OBJ_NOTNULL).

... more examples why using the macro is a good idea

bin/varnishd/cache/cache_tcp_pool.c

@@ -316,9 +316,7 @@ VCP_Recycle(const struct worker *wrk, struct pfd **pfdp)
 	int i = 0;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
-	pfd = *pfdp;
-	*pfdp = NULL;
-	CHECK_OBJ_NOTNULL(pfd, PFD_MAGIC);
+	TAKE_OBJ_NOTNULL(pfd, pfdp, PFD_MAGIC);
 	cp = pfd->conn_pool;
 	CHECK_OBJ_NOTNULL(cp, CONN_POOL_MAGIC);
 
@@ -451,9 +449,7 @@ VCP_Close(struct pfd **pfdp)
 	struct pfd *pfd;
 	struct conn_pool *cp;
 
-	pfd = *pfdp;
-	*pfdp = NULL;
-	CHECK_OBJ_NOTNULL(pfd, PFD_MAGIC);
+	TAKE_OBJ_NOTNULL(pfd, pfdp, PFD_MAGIC);
 	cp = pfd->conn_pool;
 	CHECK_OBJ_NOTNULL(cp, CONN_POOL_MAGIC);
 

bin/varnishd/cache/cache_vrt_vcl.c

@@ -123,11 +123,7 @@ VCL_Rel(struct vcl **vcc)
 {
 	struct vcl *vcl;
 
-	AN(*vcc);
-	vcl = *vcc;
-	*vcc = NULL;
-
-	CHECK_OBJ_NOTNULL(vcl, VCL_MAGIC);
+	TAKE_OBJ_NOTNULL(vcl, vcc, VCL_MAGIC);
 	Lck_Lock(&vcl_mtx);
 	assert(vcl->busy > 0);
 	vcl->busy--;

tools/coccinelle/take_obj_notnull.cocci

@@ -24,6 +24,19 @@ expression obj, objp, magic;
 expression obj, objp, magic;
 @@
 
+- AN(*objp);
+...
+- obj = *objp;
+...
+- *objp = NULL;
+...
+- CHECK_OBJ_NOTNULL(obj, magic);
++ TAKE_OBJ_NOTNULL(obj, objp, magic);
+
+@@
+expression obj, objp, magic;
+@@
+
 - AN(objp);
 ...
 - obj = *objp;
@@ -45,3 +58,14 @@ expression obj, objp, magic;
 + TAKE_OBJ_NOTNULL(obj, objp, magic);
 ...
 - *objp = NULL;
+
+@@
+expression obj, objp, magic;
+@@
+
+- obj = *objp;
+...
+- *objp = NULL;
+...
+- CHECK_OBJ_NOTNULL(obj, magic);
++ TAKE_OBJ_NOTNULL(obj, objp, magic);