[src/trunk]: src/usr.bin/xlint/lint1 lint: fix wrong 'statement not reached' ...

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

details:   https://anonhg.NetBSD.org/src/rev/05419b0039f5
branches:  trunk
changeset: 960563:05419b0039f5
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sun Mar 21 11:48:04 2021 +0000

description:
lint: fix wrong 'statement not reached' in do-while loop

diffstat:

 tests/usr.bin/xlint/lint1/msg_217.c   |  11 ++++++-----
 tests/usr.bin/xlint/lint1/msg_217.exp |   3 +--
 usr.bin/xlint/lint1/tree.c            |   7 ++++---
 3 files changed, 11 insertions(+), 10 deletions(-)

diffs (67 lines):

diff -r 41f828848309 -r 05419b0039f5 tests/usr.bin/xlint/lint1/msg_217.c
--- a/tests/usr.bin/xlint/lint1/msg_217.c       Sun Mar 21 11:38:24 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_217.c       Sun Mar 21 11:48:04 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: msg_217.c,v 1.4 2021/02/21 09:17:55 rillig Exp $       */
+/*     $NetBSD: msg_217.c,v 1.5 2021/03/21 11:48:04 rillig Exp $       */
 # 3 "msg_217.c"
 
 // Test for message: function %s falls off bottom without returning value [217]
@@ -19,16 +19,17 @@
  * Seen in external/bsd/libevent/dist/event_tagging.c, function
  * encode_int_internal.
  *
- * As of 2021-01-31, lint wrongly reports that the function would fall off
- * the bottom, but it cannot reach the bottom since every path contains the
- * 'return i'.
+ * Before tree.c 1.243 from 2021-03-21, lint wrongly reported that the
+ * 'while 0' was unreachable.  This has been fixed by allowing the 'while 0'
+ * in a do-while-false loop to be unreachable.  The same could be useful for a
+ * do-while-true.
  */
 int
 do_while_return(int i)
 {
        do {
                return i;
-       } while (/*CONSTCOND*/0);       /*FIXME*//* expect: 193 */
+       } while (0);
 }                                      /*FIXME*//* expect: 217 */
 
 /*
diff -r 41f828848309 -r 05419b0039f5 tests/usr.bin/xlint/lint1/msg_217.exp
--- a/tests/usr.bin/xlint/lint1/msg_217.exp     Sun Mar 21 11:38:24 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_217.exp     Sun Mar 21 11:48:04 2021 +0000
@@ -1,3 +1,2 @@
 msg_217.c(11): warning: function random falls off bottom without returning value [217]
-msg_217.c(31): warning: statement not reached [193]
-msg_217.c(32): warning: function do_while_return falls off bottom without returning value [217]
+msg_217.c(33): warning: function do_while_return falls off bottom without returning value [217]
diff -r 41f828848309 -r 05419b0039f5 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Sun Mar 21 11:38:24 2021 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Sun Mar 21 11:48:04 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.242 2021/03/20 21:08:09 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.243 2021/03/21 11:48:04 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 1.242 2021/03/20 21:08:09 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.243 2021/03/21 11:48:04 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -3777,7 +3777,8 @@
        }
 
        /* expr() is also called in global initializations */
-       if (dcs->d_ctx != EXTERN)
+       /* TODO: rename constcond_false_ok */
+       if (dcs->d_ctx != EXTERN && !constcond_false_ok)
                check_statement_reachable();
 
        check_expr_misc(tn, vctx, tctx, !tctx, false, false, false);