assert that VCL_INT is sufficiently large

src/vmod_shard.c

@@ -58,9 +58,9 @@ struct vmod_shard_shard {
 };
 
 /*
- * our key is a uint32_t, but VCL_INT is a (signed) long and we don't have a
- * VCL_UINT - so we cast back and forth assuming that compilers agree that using
- * a longer machine type as a container is safe
+ * our key is a uint32_t, but VCL_INT is a (signed) long.  We cast back and
+ * forth, asserting in vmod_shard__init() that VCL_INT is a large enough
+ * container
  */
 VCL_INT __match_proto__(td_shard_key)
 vmod_key(VRT_CTX, VCL_STRING s, VCL_ENUM alg_s)
@@ -78,6 +78,15 @@ vmod_shard__init(VRT_CTX, struct vmod_shard_shard **vshardp,
     const char *vcl_name)
 {
 	struct vmod_shard_shard *vshard;
+	VCL_INT t1;
+	uint32_t t2a, t2b;
+
+	/* see vmod_key comment */
+	assert(sizeof(VCL_INT) >= sizeof(uint32_t));
+	t2a = UINT32_MAX;
+	t1 = (VCL_INT)t2a;
+	t2b = (uint32_t)t1;
+	assert(t2a == t2b);
 
 	(void) ctx;
 	AN(vshardp);