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lint: make check_precedence_confusion simpler 

In C, only binary operators have possibly confusing precedence.  All
binary operators have lower precedence than an explicit cast.  When an
expression is parsed, the parentheses are associated with the innermost
possible node.  This means that as soon as a cast operator is
parenthesized, its contained expression can no longer have confusing
precedence.

This allows the code to be written more succinct since the local
variables are no longer necessary.
This commit is contained in:
rillig 2021-01-05 17:37:57 +00:00
parent 09a0c30431
commit 701a9913ea
1 changed files with 9 additions and 19 deletions
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28
usr.bin/xlint/lint1/tree.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tree.c,v 1.134 2021/01/05 00:17:21 rillig Exp $ */
/* $NetBSD: tree.c,v 1.135 2021/01/05 17:37:57 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 1.134 2021/01/05 00:17:21 rillig Exp $");
__RCSID("$NetBSD: tree.c,v 1.135 2021/01/05 17:37:57 rillig Exp $");
#endif
#include <float.h>
@ -4027,32 +4027,22 @@ is_confusing_precedence(op_t op, op_t lop, bool lparen, op_t rop, bool rparen)
static void
check_precedence_confusion(tnode_t *tn)
{
tnode_t *ln, *rn;
op_t lop, rop;
bool lparn, rparn;
mod_t *mp;
tnode_t *ln, *rn;
if (!hflag)
return;
mp = &modtab[tn->tn_op];
lint_assert(mp->m_binary);
dprint_node(tn);
lparn = false;
lint_assert(modtab[tn->tn_op].m_binary);
for (ln = tn->tn_left; ln->tn_op == CVT; ln = ln->tn_left)
lparn |= ln->tn_parenthesized;
lparn |= ln->tn_parenthesized;
lop = ln->tn_op;
rparn = false;
continue;
for (rn = tn->tn_right; rn->tn_op == CVT; rn = rn->tn_left)
rparn |= rn->tn_parenthesized;
rparn |= rn->tn_parenthesized;
rop = rn->tn_op;
continue;
if (is_confusing_precedence(tn->tn_op, lop, lparn, rop, rparn)) {
if (is_confusing_precedence(tn->tn_op,
ln->tn_op, ln->tn_parenthesized,
rn->tn_op, rn->tn_parenthesized)) {
/* precedence confusion possible: parenthesize! */
warning(169);
}