[src/trunk]: src/usr.bin/xlint/lint1 lint: do not warn about pointer cast bet...

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

details:   https://anonhg.NetBSD.org/src/rev/523cb49ccbbd
branches:  trunk
changeset: 368114:523cb49ccbbd
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Jun 24 20:16:21 2022 +0000

description:
lint: do not warn about pointer cast between sockaddr variants

diffstat:

 tests/usr.bin/xlint/lint1/msg_247.c |  35 ++++++++++++++++++++---------------
 usr.bin/xlint/lint1/tree.c          |  27 +++++++++++++++++++++++++--
 2 files changed, 45 insertions(+), 17 deletions(-)

diffs (128 lines):

diff -r b5adc8474be5 -r 523cb49ccbbd tests/usr.bin/xlint/lint1/msg_247.c
--- a/tests/usr.bin/xlint/lint1/msg_247.c       Fri Jun 24 20:02:58 2022 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_247.c       Fri Jun 24 20:16:21 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: msg_247.c,v 1.21 2022/06/24 20:02:58 rillig Exp $      */
+/*     $NetBSD: msg_247.c,v 1.22 2022/06/24 20:16:21 rillig Exp $      */
 # 3 "msg_247.c"
 
 // Test for message: pointer cast from '%s' to '%s' may be troublesome [247]
@@ -14,13 +14,14 @@
        int id;
 };
 
-void
+PDisplay
 example(struct Other *arg)
 {
-       PDisplay display;
-
        /*
-        * XXX: The target type is reported as 'struct <unnamed>'.  In cases
+        * Before tree.c 1.461 from 2022-06-24, lint warned about the cast
+        * between the structs.
+        *
+        * XXX: The target type was reported as 'struct <unnamed>'.  In cases
         *  like these, it would be helpful to print at least the type name
         *  of the pointer.  This type name though is discarded immediately
         *  in the grammar rule 'typespec: T_TYPENAME'.
@@ -28,8 +29,7 @@
         *  with no hint at all that there is a typedef for a pointer to the
         *  struct.
         */
-       /* expect+1: warning: pointer cast from 'pointer to struct Other' to 'pointer to struct <unnamed>' may be troublesome [247] */
-       display = (PDisplay)arg;
+       return (PDisplay)arg;
 }
 
 /*
@@ -249,21 +249,26 @@
        uint32_t sin6_scope_id;
 };
 
+/*
+ * Before tree.c 1.461 from 2022-06-24, lint warned about the cast between the
+ * sockaddr variants.  Since then, lint allows casts between pointers to
+ * structs if the initial members have compatible types and either of the
+ * struct types continues with a byte array.
+ */
 void *
 cast_between_sockaddr_variants(void *ptr)
 {
 
-       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr' to 'pointer to struct sockaddr_in' may be troublesome [247] */
        void *t1 = (struct sockaddr_in *)(struct sockaddr *)ptr;
-
-       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr_in' to 'pointer to struct sockaddr' may be troublesome [247] */
        void *t2 = (struct sockaddr *)(struct sockaddr_in *)t1;
-
-       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr' to 'pointer to struct sockaddr_in6' may be troublesome [247] */
        void *t3 = (struct sockaddr_in6 *)(struct sockaddr *)t2;
-
-       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr_in6' to 'pointer to struct sockaddr' may be troublesome [247] */
        void *t4 = (struct sockaddr *)(struct sockaddr_in6 *)t3;
 
-       return t4;
+       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr_in6' to 'pointer to struct sockaddr_in' may be troublesome [247] */
+       void *t5 = (struct sockaddr_in *)(struct sockaddr_in6 *)t4;
+
+       /* expect+1: warning: pointer cast from 'pointer to struct sockaddr_in' to 'pointer to struct sockaddr_in6' may be troublesome [247] */
+       void *t6 = (struct sockaddr_in6 *)(struct sockaddr_in *)t5;
+
+       return t6;
 }
diff -r b5adc8474be5 -r 523cb49ccbbd usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Fri Jun 24 20:02:58 2022 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Fri Jun 24 20:16:21 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.460 2022/06/24 19:27:43 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.461 2022/06/24 20:16:21 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: tree.c,v 1.460 2022/06/24 19:27:43 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.461 2022/06/24 20:16:21 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -2491,6 +2491,14 @@
 }
 
 static bool
+is_byte_array(const type_t *tp)
+{
+
+       return tp->t_tspec == ARRAY &&
+              (tp->t_subt->t_tspec == CHAR || tp->t_subt->t_tspec == UCHAR);
+}
+
+static bool
 should_warn_about_pointer_cast(const type_t *nstp, tspec_t nst,
                               const type_t *ostp, tspec_t ost)
 {
@@ -2512,6 +2520,21 @@
        if (ost == CHAR || ost == UCHAR)
                return false;   /* for the sake of traditional C code */
 
+       /* Allow cast between pointers to sockaddr variants. */
+       if (nst == STRUCT && ost == STRUCT) {
+               const sym_t *nmem = nstp->t_str->sou_first_member;
+               const sym_t *omem = ostp->t_str->sou_first_member;
+               while (nmem != NULL && omem != NULL &&
+                      eqtype(nmem->s_type, omem->s_type, true, false, NULL))
+                       nmem = nmem->s_next, omem = omem->s_next;
+               if (nmem != NULL && is_byte_array(nmem->s_type))
+                       return false;
+               if (omem != NULL && is_byte_array(omem->s_type))
+                       return false;
+               if (nmem == NULL && omem == NULL)
+                       return false;
+       }
+
        if (is_struct_or_union(nst) && nstp->t_str != ostp->t_str)
                return true;