[master] 177d97c1a vsb: Harden destroy and fini operations

[Nils Goroll]

commit 177d97c1a193494a30dbaeb5dfdf09e309655cd0
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Mon Sep 14 11:39:15 2020 +0200

    vsb: Harden destroy and fini operations
    
    They either take both a dynamic struct and buffer, or both are static.

diff --git a/lib/libvarnish/vsb.c b/lib/libvarnish/vsb.c
index 0cbc66305..0a185c9d6 100644
--- a/lib/libvarnish/vsb.c
+++ b/lib/libvarnish/vsb.c
@@ -529,6 +529,7 @@ VSB_fini(struct vsb *s)
 
 	assert_VSB_integrity(s);
 	assert(!VSB_ISDYNAMIC(s));
+	assert(!VSB_ISDYNSTRUCT(s));
 	memset(s, 0, sizeof(*s));
 }
 
@@ -539,6 +540,7 @@ VSB_destroy(struct vsb **s)
 	AN(s);
 	assert_VSB_integrity(*s);
 	assert(VSB_ISDYNAMIC(*s));
+	assert(VSB_ISDYNSTRUCT(*s));
 	SBFREE((*s)->s_buf);
 	memset(*s, 0, sizeof(**s));
 	SBFREE(*s);