[src/trunk]: src tests/lint: test bitwise mismatch in switch statement

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/5be84e55fe46
branches:  trunk
changeset: 983298:5be84e55fe46
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri May 14 21:14:55 2021 +0000

description:
tests/lint: test bitwise mismatch in switch statement

diffstat:

 distrib/sets/lists/tests/mi                |   3 +-
 tests/usr.bin/xlint/lint1/Makefile         |   3 +-
 tests/usr.bin/xlint/lint1/expr_range.c     |  37 ++++++++++++++++++++++++++++++
 tests/usr.bin/xlint/lint1/t_integration.sh |   3 +-
 4 files changed, 43 insertions(+), 3 deletions(-)

diffs (92 lines):

diff -r c034726b233c -r 5be84e55fe46 distrib/sets/lists/tests/mi
--- a/distrib/sets/lists/tests/mi       Fri May 14 19:37:16 2021 +0000
+++ b/distrib/sets/lists/tests/mi       Fri May 14 21:14:55 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.1049 2021/05/02 21:22:09 rillig Exp $
+# $NetBSD: mi,v 1.1050 2021/05/14 21:14:55 rillig Exp $
 #
 # Note: don't delete entries from here - mark them as "obsolete" instead.
 #
@@ -6189,6 +6189,7 @@
 ./usr/tests/usr.bin/xlint/lint1/emit.c                         tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/xlint/lint1/emit.exp                       tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/xlint/lint1/emit.ln                                tests-usr.bin-tests     compattestfile,atf
+./usr/tests/usr.bin/xlint/lint1/expr_range.c                   tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/xlint/lint1/feat_stacktrace.c              tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/xlint/lint1/feat_stacktrace.exp            tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/xlint/lint1/gcc_attribute.c                        tests-usr.bin-tests     compattestfile,atf
diff -r c034726b233c -r 5be84e55fe46 tests/usr.bin/xlint/lint1/Makefile
--- a/tests/usr.bin/xlint/lint1/Makefile        Fri May 14 19:37:16 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/Makefile        Fri May 14 21:14:55 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.55 2021/05/02 21:22:09 rillig Exp $
+# $NetBSD: Makefile,v 1.56 2021/05/14 21:14:55 rillig Exp $
 
 NOMAN=         # defined
 MAX_MESSAGE=   343             # see lint1/err.c
@@ -103,6 +103,7 @@
 FILES+=                emit.c
 FILES+=                emit.exp
 FILES+=                emit.ln
+FILES+=                expr_range.c
 FILES+=                feat_stacktrace.c
 FILES+=                feat_stacktrace.exp
 FILES+=                gcc_attribute.c
diff -r c034726b233c -r 5be84e55fe46 tests/usr.bin/xlint/lint1/expr_range.c
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/usr.bin/xlint/lint1/expr_range.c    Fri May 14 21:14:55 2021 +0000
@@ -0,0 +1,37 @@
+/*     $NetBSD: expr_range.c,v 1.1 2021/05/14 21:14:55 rillig Exp $    */
+# 3 "expr_range.c"
+
+/*
+ * Test whether lint can detect switch branches that are impossible to reach.
+ * As of 2021-05-14, it cannot.  To do this, it would need to keep track of
+ * the possible values of each variable or expression.  To do this reliably,
+ * it would also need accurate control flow analysis, which as of 2021-05-14
+ * works only for functions without 'goto'.
+ *
+ * GCC 10 does not complain the unreachable branch.  It knows that the branch
+ * is unreachable though since it doesn't generate any code for it.  GCC once
+ * had the option -Wunreachable-code, but that option was made a no-op in
+ * 2011.
+ *
+ * Clang 10 does not complain about this either, and just like GCC it doesn't
+ * generate any code for this branch.  The code for tracking an expression's
+ * possible values may be related to RangeConstraintManager, just guessing.
+ *
+ * There should be at least one static analysis tool that warns about this.
+ */
+
+/* lint1-extra-flags: -chap */
+
+void
+example(unsigned x)
+{
+       switch (x & 6) {
+       case 1:
+               /* This branch is unreachable. */
+               printf("one\n");
+               break;
+       case 2:
+               printf("two\n");
+               break;
+       }
+}
diff -r c034726b233c -r 5be84e55fe46 tests/usr.bin/xlint/lint1/t_integration.sh
--- a/tests/usr.bin/xlint/lint1/t_integration.sh        Fri May 14 19:37:16 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/t_integration.sh        Fri May 14 21:14:55 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: t_integration.sh,v 1.48 2021/05/03 03:50:43 rillig Exp $
+# $NetBSD: t_integration.sh,v 1.49 2021/05/14 21:14:55 rillig Exp $
 #
 # Copyright (c) 2008, 2010 The NetBSD Foundation, Inc.
 # All rights reserved.
@@ -175,6 +175,7 @@
 test_case d_long_double_int
 
 test_case emit
+test_case expr_range
 
 test_case gcc_attribute
 test_case gcc_attribute_aligned