Module Name: src
Committed By: rillig
Date: Mon Jul 26 17:27:22 UTC 2021
Modified Files:
src/tests/usr.bin/xlint/lint1: expr_precedence.c expr_precedence.exp
src/usr.bin/xlint/lint1: cgram.y
Log Message:
lint: fix parsing of chained assignments (since 2021-07-15)
The grammar rule for assignment_expression is quite different from those
of the other expressions, for 2 reasons: first, its precedence is
right-to-left. Second, its left-hand side must be an lvalue, which
rules out all binary operators. K&R C even had a grammar rule named
'lvalue' for this purpose. Later C standards made the kinds of
expressions more fine-grained and used 'unary_expression' in this place.
To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 src/tests/usr.bin/xlint/lint1/expr_precedence.c \
src/tests/usr.bin/xlint/lint1/expr_precedence.exp
cvs rdiff -u -r1.347 -r1.348 src/usr.bin/xlint/lint1/cgram.y
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/tests/usr.bin/xlint/lint1/expr_precedence.c
diff -u src/tests/usr.bin/xlint/lint1/expr_precedence.c:1.4 src/tests/usr.bin/xlint/lint1/expr_precedence.c:1.5
--- src/tests/usr.bin/xlint/lint1/expr_precedence.c:1.4 Mon Jul 26 17:09:46 2021
+++ src/tests/usr.bin/xlint/lint1/expr_precedence.c Mon Jul 26 17:27:22 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: expr_precedence.c,v 1.4 2021/07/26 17:09:46 rillig Exp $ */
+/* $NetBSD: expr_precedence.c,v 1.5 2021/07/26 17:27:22 rillig Exp $ */
# 3 "expr_precedence.c"
/*
@@ -42,8 +42,11 @@ assignment_associativity(int arg)
{
int left, right;
- /* FIXME */
- /* expect+1: error: left operand of '=' must be lvalue [114] */
+ /*
+ * Assignments are right-associative. If they were left-associative,
+ * the result of (left = right) would be an rvalue, resulting in this
+ * error message: 'left operand of '=' must be lvalue [114]'.
+ */
left = right = arg;
left = arg;
Index: src/tests/usr.bin/xlint/lint1/expr_precedence.exp
diff -u src/tests/usr.bin/xlint/lint1/expr_precedence.exp:1.4 src/tests/usr.bin/xlint/lint1/expr_precedence.exp:1.5
--- src/tests/usr.bin/xlint/lint1/expr_precedence.exp:1.4 Mon Jul 26 17:09:46 2021
+++ src/tests/usr.bin/xlint/lint1/expr_precedence.exp Mon Jul 26 17:27:22 2021
@@ -2,4 +2,3 @@ expr_precedence.c(15): error: syntax err
expr_precedence.c(18): error: non-constant initializer [177]
expr_precedence.c(35): error: 'var' undefined [99]
expr_precedence.c(35): error: syntax error '=' [249]
-expr_precedence.c(47): error: left operand of '=' must be lvalue [114]
Index: src/usr.bin/xlint/lint1/cgram.y
diff -u src/usr.bin/xlint/lint1/cgram.y:1.347 src/usr.bin/xlint/lint1/cgram.y:1.348
--- src/usr.bin/xlint/lint1/cgram.y:1.347 Mon Jul 26 17:15:24 2021
+++ src/usr.bin/xlint/lint1/cgram.y Mon Jul 26 17:27:22 2021
@@ -1,5 +1,5 @@
%{
-/* $NetBSD: cgram.y,v 1.347 2021/07/26 17:15:24 rillig Exp $ */
+/* $NetBSD: cgram.y,v 1.348 2021/07/26 17:27:22 rillig Exp $ */
/*
* Copyright (c) 1996 Christopher G. Demetriou. All Rights Reserved.
@@ -35,7 +35,7 @@
#include <sys/cdefs.h>
#if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: cgram.y,v 1.347 2021/07/26 17:15:24 rillig Exp $");
+__RCSID("$NetBSD: cgram.y,v 1.348 2021/07/26 17:27:22 rillig Exp $");
#endif
#include <limits.h>
@@ -691,10 +691,10 @@ conditional_expression:
/* K&R ???, C90 ???, C99 6.5.16, C11 6.5.16 */
assignment_expression:
conditional_expression
- | assignment_expression T_ASSIGN conditional_expression {
+ | unary_expression T_ASSIGN assignment_expression {
$$ = build_binary($1, ASSIGN, $3);
}
- | assignment_expression T_OPASSIGN conditional_expression {
+ | unary_expression T_OPASSIGN assignment_expression {
$$ = build_binary($1, $2, $3);
}
;
