[src/trunk]: src/usr.bin/xlint/lint1 lint: warn that bsearch effectively disc...

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

details:   https://anonhg.NetBSD.org/src/rev/9c2eff5827e6
branches:  trunk
changeset: 1024088:9c2eff5827e6
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Oct 09 20:03:20 2021 +0000

description:
lint: warn that bsearch effectively discards 'const'

Just like strchr, bsearch takes a const pointer and returns a non-const
pointer into the same object.

diffstat:

 tests/usr.bin/xlint/lint1/msg_346.c   |   8 +++---
 tests/usr.bin/xlint/lint1/msg_346.exp |   1 +
 usr.bin/xlint/lint1/tree.c            |  39 +++++++++++++++++++++++++++++++---
 3 files changed, 40 insertions(+), 8 deletions(-)

diffs (113 lines):

diff -r 01c16f07e299 -r 9c2eff5827e6 tests/usr.bin/xlint/lint1/msg_346.c
--- a/tests/usr.bin/xlint/lint1/msg_346.c       Sat Oct 09 20:00:41 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_346.c       Sat Oct 09 20:03:20 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: msg_346.c,v 1.5 2021/10/09 19:18:52 rillig Exp $       */
+/*     $NetBSD: msg_346.c,v 1.6 2021/10/09 20:03:20 rillig Exp $       */
 # 3 "msg_346.c"
 
 // Test for message: call to '%s' effectively discards 'const' from argument [346]
@@ -71,18 +71,18 @@
 int cmp(const void *, const void *);
 
 void take_void_ptr(void *);
-void take_const_void_ptr(void *);
+void take_const_void_ptr(const void *);
 
 void
 bsearch_example(void)
 {
+       int arr[] = { 1 };
        const int const_arr[] = { 1 };
-       const int arr[] = { 1 };
 
        take_const_void_ptr(bsearch("", const_arr, 4, 1, cmp));
        take_const_void_ptr(bsearch("", arr, 4, 1, cmp));
        take_void_ptr(bsearch("", arr, 4, 1, cmp));
 
-       /* TODO: expect+1: warning: call to 'bsearch' effectively discards 'const' from argument [346] */
+       /* expect+1: warning: call to 'bsearch' effectively discards 'const' from argument [346] */
        take_void_ptr(bsearch("", const_arr, 4, 1, cmp));
 }
diff -r 01c16f07e299 -r 9c2eff5827e6 tests/usr.bin/xlint/lint1/msg_346.exp
--- a/tests/usr.bin/xlint/lint1/msg_346.exp     Sat Oct 09 20:00:41 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_346.exp     Sat Oct 09 20:03:20 2021 +0000
@@ -7,3 +7,4 @@
 msg_346.c(50): warning: call to 'strrchr' effectively discards 'const' from argument [346]
 msg_346.c(52): warning: call to 'strstr' effectively discards 'const' from argument [346]
 msg_346.c(60): error: argument mismatch: 0 arg passed, 2 expected [150]
+msg_346.c(87): warning: call to 'bsearch' effectively discards 'const' from argument [346]
diff -r 01c16f07e299 -r 9c2eff5827e6 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Sat Oct 09 20:00:41 2021 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Sat Oct 09 20:03:20 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.383 2021/09/26 14:52:37 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.384 2021/10/09 20:03:20 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 1.383 2021/09/26 14:52:37 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.384 2021/10/09 20:03:20 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -1412,7 +1412,16 @@
 }
 
 static bool
-is_first_arg_const(const tnode_t *tn)
+is_const_pointer(const tnode_t *tn)
+{
+       const type_t *tp;
+
+       tp = before_conversion(tn)->tn_type;
+       return tp->t_tspec == PTR && tp->t_subt->t_const;
+}
+
+static bool
+is_first_arg_const_char_pointer(const tnode_t *tn)
 {
        const tnode_t *an;
 
@@ -1425,6 +1434,20 @@
        return is_const_char_pointer(an->tn_left);
 }
 
+static bool
+is_second_arg_const_pointer(const tnode_t *tn)
+{
+       const tnode_t *an;
+
+       an = tn->tn_right;
+       if (an == NULL || an->tn_right == NULL)
+               return false;
+
+       while (an->tn_right->tn_right != NULL)
+               an = an->tn_right;
+       return is_const_pointer(an->tn_left);
+}
+
 static void
 check_unconst_function(const type_t *lstp, const tnode_t *rn)
 {
@@ -1433,7 +1456,15 @@
        if (lstp->t_tspec == CHAR && !lstp->t_const &&
            is_direct_function_call(rn, &function_name) &&
            is_unconst_function(function_name) &&
-           is_first_arg_const(rn)) {
+           is_first_arg_const_char_pointer(rn)) {
+               /* call to '%s' effectively discards 'const' from argument */
+               warning(346, function_name);
+       }
+
+       if (!lstp->t_const &&
+           is_direct_function_call(rn, &function_name) &&
+           strcmp(function_name, "bsearch") == 0 &&
+           is_second_arg_const_pointer(rn)) {
                /* call to '%s' effectively discards 'const' from argument */
                warning(346, function_name);
        }