Unify bespoke error messages to "Symbol not found" before things

get too confusing.

bin/varnishtest/tests/r01837.vtc

 varnishtest "Test VCC errors out if probe is used before it is defined"
 
-varnish v1 -errvcl "Probe not found: 'p'" {
+varnish v1 -errvcl "Symbol not found: 'p'" {
 	backend b {
 		.host = "127.0.0.1";
 		.probe = p;

bin/varnishtest/tests/v00018.vtc

@@ -133,7 +133,7 @@ varnish v1 -errvcl {Symbol 'vcl_recv' has wrong type (sub):} {
 	}
 }
 
-varnish v1 -syntax 4.0 -errvcl {Not a VCL label:} {
+varnish v1 -syntax 4.0 -errvcl {Symbol not found:} {
 	sub vcl_recv {
 		return (vcl(vcl_recv));
 	}

bin/varnishtest/tests/v00019.vtc

@@ -64,7 +64,7 @@ varnish v1 -errvcl {Comparison of different types: STRING '==' INT} {
 	}
 }
 
-varnish v1 -errvcl {Unknown variable: 'req.http.req.http.foo'} {
+varnish v1 -errvcl {Symbol not found: 'req.http.req.http.foo'} {
 	backend b { .host = "127.0.0.1"; }
 	sub vcl_recv {
 		set req.http.req.http.foo = "bar";

bin/varnishtest/tests/v00021.vtc

@@ -91,7 +91,7 @@ varnish v1 -vcl {
 	}
 }
 
-varnish v1 -errvcl {Unknown variable: 'req.foobar'} {
+varnish v1 -errvcl {Symbol not found: 'req.foobar'} {
 	backend foo { .host = "127.0.0.1"; }
 	sub vcl_recv { set req.foobar = 3; }
 }

lib/libvcc/vcc_action.c

@@ -94,7 +94,7 @@ vcc_act_set(struct vcc *tl, struct token *t, struct symbol *sym)
 	(void)t;
 	ExpectErr(tl, ID);
 	t = tl->t;
-	sym = VCC_SymbolGet(tl, SYM_VAR, "Unknown variable", XREF_NONE);
+	sym = VCC_SymbolGet(tl, SYM_VAR, SYMTAB_EXISTING, XREF_NONE);
 	ERRCHK(tl);
 	AN(sym);
 	if (sym->w_methods == 0) {
@@ -146,7 +146,7 @@ vcc_act_unset(struct vcc *tl, struct token *t, struct symbol *sym)
 	/* XXX: Wrong, should use VCC_Expr(HEADER) */
 	ExpectErr(tl, ID);
 	t = tl->t;
-	sym = VCC_SymbolGet(tl, SYM_VAR, "Unknown variable", XREF_NONE);
+	sym = VCC_SymbolGet(tl, SYM_VAR, SYMTAB_EXISTING, XREF_NONE);
 	ERRCHK(tl);
 	AN(sym);
 	if (sym->u_methods == 0) {
@@ -269,7 +269,7 @@ vcc_act_return_vcl(struct vcc *tl)
 	ExpectErr(tl, '(');
 	vcc_NextToken(tl);
 	ExpectErr(tl, ID);
-	sym = VCC_SymbolGet(tl, SYM_VCL, "Not a VCL label", XREF_NONE);
+	sym = VCC_SymbolGet(tl, SYM_VCL, SYMTAB_EXISTING, XREF_NONE);
 	ERRCHK(tl);
 	AN(sym);
 	if (sym->eval_priv == NULL) {

lib/libvcc/vcc_backend.c

@@ -432,7 +432,7 @@ vcc_ParseHostDef(struct vcc *tl, const struct token *t_be, const char *vgcname)
 				(void)vcc_default_probe(tl);
 			} else {
 				pb = VCC_SymbolGet(tl, SYM_PROBE,
-				    "Probe not found", XREF_REF);
+				    SYMTAB_EXISTING, XREF_REF);
 				ERRCHK(tl);
 				AN(pb);
 				Fb(tl, 0, "\t.probe = %s,\n", pb->rname);
@@ -540,6 +540,7 @@ vcc_ParseBackend(struct vcc *tl)
 	} else {
 		sym = VCC_HandleSymbol(tl, BACKEND, "vgc_backend");
 		ERRCHK(tl);
+		AN(sym);
 		dn = sym->rname;
 		if (tl->default_director == NULL) {
 			tl->first_director = sym;

lib/libvcc/vcc_compile.h

@@ -350,13 +350,19 @@ void vcc_stevedore(struct vcc *vcc, const char *stv_name);
 /* vcc_symb.c */
 void VCC_PrintCName(struct vsb *vsb, const char *b, const char *e);
 struct symbol *VCC_MkSym(struct vcc *tl, const char *b, vcc_kind_t, int, int);
-extern const char XREF_NONE[];
-extern const char XREF_DEF[];
-extern const char XREF_REF[];
-extern const char SYMTAB_NOERR[];
-extern const char SYMTAB_CREATE[];
-struct symbol *VCC_SymbolGet(struct vcc *, vcc_kind_t, const char *,
-    const char *);
+
+struct symxref { const char *name; };
+extern const struct symxref XREF_NONE[1];
+extern const struct symxref XREF_DEF[1];
+extern const struct symxref XREF_REF[1];
+
+struct symmode { const char *name; };
+extern const struct symmode SYMTAB_NOERR[1];
+extern const struct symmode SYMTAB_CREATE[1];
+extern const struct symmode SYMTAB_EXISTING[1];
+
+struct symbol *VCC_SymbolGet(struct vcc *, vcc_kind_t,
+    const struct symmode *, const struct symxref *);
 
 typedef void symwalk_f(struct vcc *tl, const struct symbol *s);
 void VCC_WalkSymbols(struct vcc *tl, symwalk_f *func, vcc_kind_t);

lib/libvcc/vcc_expr.c

@@ -688,8 +688,7 @@ vcc_expr4(struct vcc *tl, struct expr **e, vcc_type_t fmt)
 	switch (tl->t->tok) {
 	case ID:
 		t = tl->t;
-		sym = VCC_SymbolGet(tl, SYM_NONE, "Symbol not found",
-		    XREF_REF);
+		sym = VCC_SymbolGet(tl, SYM_NONE, SYMTAB_EXISTING, XREF_REF);
 		ERRCHK(tl);
 		AN(sym);
 		if (sym->kind == SYM_FUNC && sym->type == VOID) {

lib/libvcc/vcc_symb.c

@@ -226,19 +226,25 @@ vcc_sym_in_tab(struct vcc *tl, struct symtab *st,
 }
 
 
-const char XREF_NONE[] = "xref_none";
-const char XREF_DEF[] = "xref_def";
-const char XREF_REF[] = "xref_ref";
-const char SYMTAB_NOERR[] = "sym_noerror";
-const char SYMTAB_CREATE[] = "sym_create";
+const struct symxref XREF_NONE[1] = {{"xref_none"}};
+const struct symxref XREF_DEF[1] = {{"xref_def"}};
+const struct symxref XREF_REF[1] = {{"xref_ref"}};
+const struct symmode SYMTAB_NOERR[1] = {{"sym_noerror"}};
+const struct symmode SYMTAB_CREATE[1] = {{"sym_create"}};
+const struct symmode SYMTAB_EXISTING[1] = {{"Symbol not found"}};
 
 struct symbol *
-VCC_SymbolGet(struct vcc *tl, vcc_kind_t kind, const char *e, const char *x)
+VCC_SymbolGet(struct vcc *tl, vcc_kind_t kind,
+    const struct symmode *e, const struct symxref *x)
 {
 	struct symtab *st;
 	struct symbol *sym;
 	struct token *t0, *tn, *tn1;
 
+	AN(tl);
+	AN(e);
+	AN(x);
+	AN(x->name);
 	if (tl->syntax >= VCL_41 && e == SYMTAB_CREATE && kind != SYM_SUB &&
 	    (tl->t->b[0] == 'v'|| tl->t->b[0] == 'V') &&
 	    (tl->t->b[1] == 'c'|| tl->t->b[1] == 'C') &&
@@ -270,7 +276,7 @@ VCC_SymbolGet(struct vcc *tl, vcc_kind_t kind, const char *e, const char *x)
 		return (sym);
 	tl->t = VTAILQ_NEXT(tn, list);
 	if (sym == NULL) {
-		VSB_printf(tl->sb, "%s: '", e);
+		VSB_printf(tl->sb, "%s: '", e->name);
 		for (tn1 = t0; tn1 != tl->t; tn1 = VTAILQ_NEXT(tn1, list))
 			VSB_printf(tl->sb, "%.*s", PF(tn1));
 		VSB_printf(tl->sb, "'");

lib/libvcc/vcc_vmod.c

@@ -402,7 +402,7 @@ vcc_Act_New(struct vcc *tl, struct token *t, struct symbol *sym)
 
 	ExpectErr(tl, ID);
 	t = tl->t;
-	sy2 = VCC_SymbolGet(tl, SYM_OBJECT, "Symbol not found", XREF_NONE);
+	sy2 = VCC_SymbolGet(tl, SYM_OBJECT, SYMTAB_EXISTING, XREF_NONE);
 	ERRCHK(tl);
 	AN(sy2);
 	if (sy2->eval_priv == NULL) {