From 598b5fa38753b399bc198402794e93ab7b772b7e Mon Sep 17 00:00:00 2001
From: rillig <rillig@NetBSD.org>
Date: Tue, 19 Apr 2022 23:16:14 +0000
Subject: [PATCH] lint: fix integer overflow on seeing -(uint64_t)INT64_MIN

Seen in external/cddl/osnet/dist/lib/libuutil/common/uu_strtoint.c,
which is protected by a NOLINT in ../Makefile.inc.
---
 tests/usr.bin/xlint/lint1/expr_fold.c   | 15 ++++++++++++++-
 tests/usr.bin/xlint/lint1/expr_fold.exp |  1 +
 usr.bin/xlint/lint1/tree.c              |  6 +++---
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/tests/usr.bin/xlint/lint1/expr_fold.c b/tests/usr.bin/xlint/lint1/expr_fold.c
index e4ef9e557ef4..07ac4bd9a1cc 100644
--- a/tests/usr.bin/xlint/lint1/expr_fold.c
+++ b/tests/usr.bin/xlint/lint1/expr_fold.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: expr_fold.c,v 1.6 2022/04/15 21:50:07 rillig Exp $	*/
+/*	$NetBSD: expr_fold.c,v 1.7 2022/04/19 23:16:14 rillig Exp $	*/
 # 3 "expr_fold.c"
 
 /*
@@ -287,3 +287,16 @@ struct ctassert5_struct {
 		? 1
 		: -1;
 };
+
+/*
+ * Since Makefile.inc 1.21 from 2022-04-08 (which added -ftrapv) and before
+ * tree.c 1.436 from 2022-04-20, lint crashed with an integer overflow when
+ * calculating '-(uint64_t)INT64_MIN' in val_t.v_quad.
+ */
+void
+unary_minus_overflow(unsigned long long val)
+{
+	/* expect+1: warning: integer overflow detected, op '-' [141] */
+	if (val > -(unsigned long long)(-0x7fffffffffffffffL - 1))
+		return;
+}
diff --git a/tests/usr.bin/xlint/lint1/expr_fold.exp b/tests/usr.bin/xlint/lint1/expr_fold.exp
index b65b808d4c02..64611f1b2258 100644
--- a/tests/usr.bin/xlint/lint1/expr_fold.exp
+++ b/tests/usr.bin/xlint/lint1/expr_fold.exp
@@ -32,3 +32,4 @@ expr_fold.c(183): warning: integer overflow detected, op '<<' [141]
 expr_fold.c(186): warning: integer overflow detected, op '<<' [141]
 expr_fold.c(190): warning: shift amount 104 is greater than bit-size 32 of 'unsigned int' [122]
 expr_fold.c(202): warning: shift amount 104 is greater than bit-size 32 of 'int' [122]
+expr_fold.c(300): warning: integer overflow detected, op '-' [141]
diff --git a/usr.bin/xlint/lint1/tree.c b/usr.bin/xlint/lint1/tree.c
index 19595a6da3dd..adf217b53ca0 100644
--- a/usr.bin/xlint/lint1/tree.c
+++ b/usr.bin/xlint/lint1/tree.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tree.c,v 1.435 2022/04/19 22:14:30 rillig Exp $	*/
+/*	$NetBSD: tree.c,v 1.436 2022/04/19 23:16:14 rillig Exp $	*/
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: tree.c,v 1.435 2022/04/19 22:14:30 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.436 2022/04/19 23:16:14 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -3210,7 +3210,7 @@ fold(tnode_t *tn)
 		q = sl;
 		break;
 	case UMINUS:
-		q = -sl;
+		q = sl == INT64_MIN ? sl : -sl;
 		if (sl != 0 && msb(q, t) == msb(sl, t))
 			ovfl = true;
 		break;