From 435454f6041216d2c38e507c860737c23e3e50fc Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Sun, 24 Feb 2019 16:11:16 -0800
Subject: Check for negative array lengths/indices

---
 decl.c | 8 ++++----
 expr.c | 4 +++-
 expr.h | 2 +-
 init.c | 2 +-
 stmt.c | 2 +-
 5 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/decl.c b/decl.c
index ac72f23..870d72a 100644
--- a/decl.c
+++ b/decl.c
@@ -212,7 +212,7 @@ tagspec(struct scope *s)
 			scopeputdecl(s, tok.lit, d);
 			next();
 			if (consume(TASSIGN))
-				i = intconstexpr(s);
+				i = intconstexpr(s, true);
 			d->value = mkintconst(t->repr, i);
 			if (!consume(TCOMMA))
 				break;
@@ -336,7 +336,7 @@ declspecs(struct scope *s, enum storageclass *sc, enum funcspecifier *fs, int *a
 			if (t) {
 				*align = t->align;
 			} else {
-				i = intconstexpr(s);
+				i = intconstexpr(s, false);
 				if (!i || i & (i - 1) || i > 16)
 					error(&tok.loc, "invalid alignment: %d", i);
 				*align = (int)i;
@@ -511,7 +511,7 @@ declaratortypes(struct scope *s, struct list *result, char **name, bool allowabs
 				i = 0;
 				next();
 			} else {
-				i = intconstexpr(s);
+				i = intconstexpr(s, false);
 				expect(TRBRACK, "after array length");
 			}
 			if (tq) {
@@ -712,7 +712,7 @@ decl(struct scope *s, struct function *f)
 
 	if (consume(T_STATIC_ASSERT)) {
 		expect(TLPAREN, "after _Static_assert");
-		c = intconstexpr(s);
+		c = intconstexpr(s, true);
 		expect(TCOMMA, "after static assertion expression");
 		expect(TSTRINGLIT, "after static assertion expression");
 		if (!c)
diff --git a/expr.c b/expr.c
index 501e0e5..a09f2d6 100644
--- a/expr.c
+++ b/expr.c
@@ -847,13 +847,15 @@ condexpr(struct scope *s)
 }
 
 uint64_t
-intconstexpr(struct scope *s)
+intconstexpr(struct scope *s, bool allowneg)
 {
 	struct expression *e;
 
 	e = eval(condexpr(s));
 	if (e->kind != EXPRCONST || !(typeprop(e->type) & PROPINT))
 		error(&tok.loc, "not an integer constant expression");
+	if (!allowneg && e->type->basic.issigned && e->constant.i > INT64_MAX)
+		error(&tok.loc, "integer constant expression cannot be negative");
 	return e->constant.i;
 }
 
diff --git a/expr.h b/expr.h
index 7de6635..8e7aa4c 100644
--- a/expr.h
+++ b/expr.h
@@ -88,7 +88,7 @@ struct scope;
 
 struct expression *expr(struct scope *);
 struct expression *assignexpr(struct scope *);
-uint64_t intconstexpr(struct scope *);
+uint64_t intconstexpr(struct scope *, _Bool);
 void delexpr(struct expression *);
 
 void exprpromote(struct expression **);  // XXX: move to type
diff --git a/init.c b/init.c
index ec76ef3..20e2f51 100644
--- a/init.c
+++ b/init.c
@@ -129,7 +129,7 @@ designator(struct scope *s, struct initparser *p)
 			if (t->kind != TYPEARRAY)
 				error(&tok.loc, "index designator is only valid for array types");
 			next();
-			p->sub->idx = intconstexpr(s);
+			p->sub->idx = intconstexpr(s, false);
 			if (t->incomplete)
 				updatearray(t, p->sub->idx);
 			else if (p->sub->idx >= t->array.length)
diff --git a/stmt.c b/stmt.c
index a5192c5..e642353 100644
--- a/stmt.c
+++ b/stmt.c
@@ -52,7 +52,7 @@ stmt(struct function *f, struct scope *s)
 			error(&tok.loc, "'case' label must be in switch");
 		label[0] = mkblock("switch_case");
 		funclabel(f, label[0]);
-		i = intconstexpr(s);
+		i = intconstexpr(s, true);
 		switchcase(s->switchcases, i, label[0]);
 		expect(TCOLON, "after case expression");
 		stmt(f, s);
-- 
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