[src/trunk]: src/usr.bin/xlint/lint1 lint: allow pointer cast between compati...

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

details:   https://anonhg.NetBSD.org/src/rev/b8aaa45ff743
branches:  trunk
changeset: 368116:b8aaa45ff743
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Jun 24 20:44:53 2022 +0000

description:
lint: allow pointer cast between compatible structs

Lint already allowed pointer casts from 'struct counter' to 'struct
counter_impl'.  Now it also allows the other direction.

diffstat:

 tests/usr.bin/xlint/lint1/msg_247.c |   8 ++++----
 usr.bin/xlint/lint1/tree.c          |  23 ++++++++++++++---------
 2 files changed, 18 insertions(+), 13 deletions(-)

diffs (82 lines):

diff -r c1d812f786f5 -r b8aaa45ff743 tests/usr.bin/xlint/lint1/msg_247.c
--- a/tests/usr.bin/xlint/lint1/msg_247.c       Fri Jun 24 20:32:12 2022 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_247.c       Fri Jun 24 20:44:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: msg_247.c,v 1.23 2022/06/24 20:32:12 rillig Exp $      */
+/*     $NetBSD: msg_247.c,v 1.24 2022/06/24 20:44:53 rillig Exp $      */
 # 3 "msg_247.c"
 
 // Test for message: pointer cast from '%s' to '%s' may be troublesome [247]
@@ -117,7 +117,7 @@
        struct counter_impl *impl = allocate();
        impl->public_part.count = 12345;
        impl->saved_count = 12346;
-       /* expect+1: warning: pointer cast from 'pointer to struct counter_impl' to 'pointer to struct counter' may be troublesome [247] */
+       /* Before tree.c 1.462 from 2022-06-24, lint warned about this cast. */
        return (struct counter *)impl;
 }
 
@@ -296,9 +296,9 @@
 } ctl_named_node_t;
 
 void *
-cast_between_initial_struct(void *ptr)
+cast_between_first_member_struct(void *ptr)
 {
-       /* expect+1: warning: pointer cast from 'pointer to struct ctl_named_node_s' to 'pointer to struct ctl_node_s' may be troublesome [247] */
+       /* Before tree.c 1.462 from 2022-06-24, lint warned about this cast. */
        void *t1 = (ctl_node_t *)(ctl_named_node_t *)ptr;
 
        void *t2 = (ctl_named_node_t *)(ctl_node_t *)ptr;
diff -r c1d812f786f5 -r b8aaa45ff743 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Fri Jun 24 20:32:12 2022 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Fri Jun 24 20:44:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.461 2022/06/24 20:16:21 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.462 2022/06/24 20:44:53 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: tree.c,v 1.461 2022/06/24 20:16:21 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.462 2022/06/24 20:44:53 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -2491,6 +2491,15 @@
 }
 
 static bool
+struct_starts_with(const type_t *struct_tp, const type_t *member_tp)
+{
+
+       return struct_tp->t_str->sou_first_member != NULL &&
+              eqtype(struct_tp->t_str->sou_first_member->s_type, member_tp,
+                  true, false, NULL);
+}
+
+static bool
 is_byte_array(const type_t *tp)
 {
 
@@ -2502,14 +2511,10 @@
 should_warn_about_pointer_cast(const type_t *nstp, tspec_t nst,
                               const type_t *ostp, tspec_t ost)
 {
-       /*
-        * Casting a pointer to 'struct S' to a pointer to another struct that
-        * has 'struct S' as its first member is ok, see msg_247.c, 'struct
-        * counter'.
-        */
+
        if (nst == STRUCT && ost == STRUCT &&
-           nstp->t_str->sou_first_member != NULL &&
-           nstp->t_str->sou_first_member->s_type == ostp)
+           (struct_starts_with(nstp, ostp) ||
+            struct_starts_with(ostp, nstp)))
                return false;
 
        if (is_incomplete(nstp) || is_incomplete(ostp))