[src/trunk]: src/usr.bin/xlint/lint1 lint: reduce negations in typeok_point, ...

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

details:   https://anonhg.NetBSD.org/src/rev/4c493d899076
branches:  trunk
changeset: 366208:4c493d899076
user:      rillig <rillig%NetBSD.org@localhost>
date:      Wed May 18 20:01:21 2022 +0000

description:
lint: reduce negations in typeok_point, document check_expr_misc

No functional change.

diffstat:

 usr.bin/xlint/lint1/tree.c |  49 +++++++++++++++++++++++++++++++++++----------
 1 files changed, 38 insertions(+), 11 deletions(-)

diffs (77 lines):

diff -r 42c288dcec06 -r 4c493d899076 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Wed May 18 19:29:00 2022 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Wed May 18 20:01:21 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.439 2022/04/30 22:31:23 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.440 2022/05/18 20:01:21 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 1.439 2022/04/30 22:31:23 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.440 2022/05/18 20:01:21 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -788,15 +788,28 @@
 static bool
 typeok_point(const tnode_t *ln, const type_t *ltp, tspec_t lt)
 {
-       if (lt == FUNC || lt == VOID || ltp->t_bitfield ||
-           ((lt != STRUCT && lt != UNION) && !ln->tn_lvalue)) {
-               /* With allow_c90 we already got an error */
-               if (!allow_c90)
-                       /* unacceptable operand of '%s' */
-                       error(111, op_name(POINT));
-               return false;
-       }
-       return true;
+       if (is_struct_or_union(lt))
+               return true;
+
+       if (lt == FUNC || lt == VOID || ltp->t_bitfield)
+               goto wrong;
+
+       /*
+        * Some C dialects from before C90 tolerated any lvalue on the
+        * left-hand side of the '.' operator, allowing things like
+        * char st[100]; st.st_mtime, assuming that the member 'st_mtime'
+        * only occurred in a single struct; see typeok_arrow.
+        */
+       if (ln->tn_lvalue)
+               return true;
+
+wrong:
+       /* With allow_c90 we already got an error */
+       if (!allow_c90)
+               /* unacceptable operand of '%s' */
+               error(111, op_name(POINT));
+
+       return false;
 }
 
 static bool
@@ -4196,6 +4209,20 @@
        return true;
 }
 
+/*
+ *     vctx                    ???
+ *     cond                    whether the expression is a condition that
+ *                             will be compared with 0
+ *     eqwarn                  whether the operator '==' might be a
+ *                             misspelled '='
+ *     fcall                   whether the expression is a function call
+ *     retval_discarded        whether the return value of a function call
+ *                             is discarded; such calls will be analyzed by
+ *                             lint2 in messages 4, 8 and 9
+ *     szof                    whether the expression is part of a sizeof
+ *                             expression, which means that its value is
+ *                             discarded since only the type is relevant
+ */
 void
 check_expr_misc(const tnode_t *tn, bool vctx, bool cond,
                bool eqwarn, bool fcall, bool retval_discarded, bool szof)