From b4f89ba90b6ca3233cc80aef9d42055266fac8df Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Thu, 1 Jul 2021 01:51:42 -0700
Subject: decl: Check that the flexible array member (if present) is last

---
 cc.h   |  2 +-
 decl.c | 12 +++++++++---
 type.c |  3 ++-
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/cc.h b/cc.h
index 774c951..87d4460 100644
--- a/cc.h
+++ b/cc.h
@@ -209,7 +209,7 @@ struct type {
 	};
 	/* qualifiers of the base type */
 	enum typequal qual;
-	_Bool incomplete;
+	_Bool incomplete, flexible;
 	union {
 		struct {
 			_Bool issigned, iscomplex;
diff --git a/decl.c b/decl.c
index 8912c6a..7460d04 100644
--- a/decl.c
+++ b/decl.c
@@ -685,11 +685,17 @@ addmember(struct structbuilder *b, struct qualtype mt, char *name, int align, ui
 	struct member *m;
 	size_t end;
 
-	/* XXX: flexible array member must be last */
-	if (mt.type->incomplete && mt.type->kind != TYPEARRAY)
-		error(&tok.loc, "struct member '%s' has incomplete type", name);
+	if (t->flexible)
+		error(&tok.loc, "struct member '%s' is after flexible array member", name);
+	if (mt.type->incomplete) {
+		if (mt.type->kind != TYPEARRAY)
+			error(&tok.loc, "struct member '%s' has incomplete type", name);
+		t->flexible = true;
+	}
 	if (mt.type->kind == TYPEFUNC)
 		error(&tok.loc, "struct member '%s' has function type", name);
+	if (mt.type->flexible)
+		error(&tok.loc, "struct member '%s' contains flexible array member", name);
 	assert(mt.type->align > 0);
 	if (name || width == -1) {
 		m = xmalloc(sizeof(*m));
diff --git a/type.c b/type.c
index 1c6888f..39f656f 100644
--- a/type.c
+++ b/type.c
@@ -61,7 +61,8 @@ mktype(enum typekind kind, enum typeprop prop)
 	t->kind = kind;
 	t->prop = prop;
 	t->value = NULL;
-	t->incomplete = 0;
+	t->incomplete = false;
+	t->flexible = false;
 
 	return t;
 }
-- 
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