Module Name: src
Committed By: rillig
Date: Sat May 15 19:12:15 UTC 2021
Modified Files:
src/tests/usr.bin/xlint/lint1: Makefile expr_range.c
src/usr.bin/xlint/lint1: func.c lint1.h
Log Message:
lint: warn about unreachable case labels for '&&'
See octeon_gmxreg.h 1.2 from 2020-06-18 for an example, where
RXN_RX_INBND_SPEED was cleaned up without adjusting the corresponding
code in octeon_gmx.c.
To generate a diff of this commit:
cvs rdiff -u -r1.56 -r1.57 src/tests/usr.bin/xlint/lint1/Makefile
cvs rdiff -u -r1.1 -r1.2 src/tests/usr.bin/xlint/lint1/expr_range.c
cvs rdiff -u -r1.107 -r1.108 src/usr.bin/xlint/lint1/func.c
cvs rdiff -u -r1.100 -r1.101 src/usr.bin/xlint/lint1/lint1.h
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/Makefile
diff -u src/tests/usr.bin/xlint/lint1/Makefile:1.56 src/tests/usr.bin/xlint/lint1/Makefile:1.57
--- src/tests/usr.bin/xlint/lint1/Makefile:1.56 Fri May 14 21:14:55 2021
+++ src/tests/usr.bin/xlint/lint1/Makefile Sat May 15 19:12:14 2021
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.56 2021/05/14 21:14:55 rillig Exp $
+# $NetBSD: Makefile,v 1.57 2021/05/15 19:12:14 rillig Exp $
NOMAN= # defined
MAX_MESSAGE= 343 # see lint1/err.c
@@ -104,6 +104,7 @@ FILES+= emit.c
FILES+= emit.exp
FILES+= emit.ln
FILES+= expr_range.c
+FILES+= expr_range.exp
FILES+= feat_stacktrace.c
FILES+= feat_stacktrace.exp
FILES+= gcc_attribute.c
Index: src/tests/usr.bin/xlint/lint1/expr_range.c
diff -u src/tests/usr.bin/xlint/lint1/expr_range.c:1.1 src/tests/usr.bin/xlint/lint1/expr_range.c:1.2
--- src/tests/usr.bin/xlint/lint1/expr_range.c:1.1 Fri May 14 21:14:55 2021
+++ src/tests/usr.bin/xlint/lint1/expr_range.c Sat May 15 19:12:14 2021
@@ -1,37 +1,43 @@
-/* $NetBSD: expr_range.c,v 1.1 2021/05/14 21:14:55 rillig Exp $ */
+/* $NetBSD: expr_range.c,v 1.2 2021/05/15 19:12:14 rillig Exp $ */
# 3 "expr_range.c"
/*
- * Test whether lint can detect switch branches that are impossible to reach.
- * As of 2021-05-14, it cannot. To do this, it would need to keep track of
- * the possible values of each variable or expression. To do this reliably,
- * it would also need accurate control flow analysis, which as of 2021-05-14
- * works only for functions without 'goto'.
+ * In a switch statement that has (expr & constant) as the controlling
+ * expression, complain if one of the case branches is unreachable because
+ * the case label does can never match the controlling expression.
*
- * GCC 10 does not complain the unreachable branch. It knows that the branch
- * is unreachable though since it doesn't generate any code for it. GCC once
- * had the option -Wunreachable-code, but that option was made a no-op in
- * 2011.
+ * GCC 10 does not complain about the unreachable branch. It knows that the
+ * branch is unreachable though since it doesn't generate any code for it.
+ * GCC once had the option -Wunreachable-code, but that option was made a
+ * no-op in 2011.
*
* Clang 10 does not complain about this either, and just like GCC it doesn't
* generate any code for this branch. The code for tracking an expression's
* possible values may be related to RangeConstraintManager, just guessing.
- *
- * There should be at least one static analysis tool that warns about this.
*/
/* lint1-extra-flags: -chap */
+void println(const char *);
+
void
example(unsigned x)
{
switch (x & 6) {
- case 1:
- /* This branch is unreachable. */
- printf("one\n");
+ case 0:
+ println("0 is reachable");
+ break;
+ case 1: /* expect: statement not reached */
+ println("1 is not reachable");
break;
case 2:
- printf("two\n");
+ println("2 is reachable");
+ break;
+ case 6:
+ println("6 is reachable");
+ break;
+ case 7: /* expect: statement not reached */
+ println("7 is not reachable");
break;
}
}
Index: src/usr.bin/xlint/lint1/func.c
diff -u src/usr.bin/xlint/lint1/func.c:1.107 src/usr.bin/xlint/lint1/func.c:1.108
--- src/usr.bin/xlint/lint1/func.c:1.107 Mon May 3 07:08:54 2021
+++ src/usr.bin/xlint/lint1/func.c Sat May 15 19:12:14 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: func.c,v 1.107 2021/05/03 07:08:54 rillig Exp $ */
+/* $NetBSD: func.c,v 1.108 2021/05/15 19:12:14 rillig Exp $ */
/*
* Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
#include <sys/cdefs.h>
#if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: func.c,v 1.107 2021/05/03 07:08:54 rillig Exp $");
+__RCSID("$NetBSD: func.c,v 1.108 2021/05/15 19:12:14 rillig Exp $");
#endif
#include <stdlib.h>
@@ -440,6 +440,25 @@ named_label(sym_t *sym)
}
static void
+check_case_label_bitand(const tnode_t *case_expr, const tnode_t *switch_expr)
+{
+ uint64_t case_value, mask;
+
+ if (switch_expr->tn_op != BITAND ||
+ switch_expr->tn_right->tn_op != CON)
+ return;
+
+ lint_assert(case_expr->tn_op == CON);
+ case_value = case_expr->tn_val->v_quad;
+ mask = switch_expr->tn_right->tn_val->v_quad;
+
+ if ((case_value & ~mask) != 0) {
+ /* statement not reached */
+ warning(193);
+ }
+}
+
+static void
check_case_label_enum(const tnode_t *tn, const cstk_t *ci)
{
/* similar to typeok_enum in tree.c */
@@ -483,6 +502,7 @@ check_case_label(tnode_t *tn, cstk_t *ci
return;
}
+ check_case_label_bitand(tn, ci->c_switch_expr);
check_case_label_enum(tn, ci);
lint_assert(ci->c_switch_type != NULL);
@@ -694,12 +714,16 @@ switch1(tnode_t *tn)
tp->t_tspec = INT;
}
+ /* leak the memory, for check_case_label_bitand */
+ expr_save_memory();
+
check_getopt_begin_switch();
- expr(tn, true, false, true, false);
+ expr(tn, true, false, false, false);
begin_control_statement(CS_SWITCH);
cstmt->c_switch = true;
cstmt->c_switch_type = tp;
+ cstmt->c_switch_expr = tn;
set_reached(false);
seen_fallthrough = true;
Index: src/usr.bin/xlint/lint1/lint1.h
diff -u src/usr.bin/xlint/lint1/lint1.h:1.100 src/usr.bin/xlint/lint1/lint1.h:1.101
--- src/usr.bin/xlint/lint1/lint1.h:1.100 Sun Apr 18 17:47:32 2021
+++ src/usr.bin/xlint/lint1/lint1.h Sat May 15 19:12:14 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: lint1.h,v 1.100 2021/04/18 17:47:32 rillig Exp $ */
+/* $NetBSD: lint1.h,v 1.101 2021/05/15 19:12:14 rillig Exp $ */
/*
* Copyright (c) 1996 Christopher G. Demetriou. All Rights Reserved.
@@ -416,6 +416,7 @@ typedef struct control_statement {
bool c_had_return_value : 1; /* had "return expr;" */
type_t *c_switch_type; /* type of switch expression */
+ tnode_t *c_switch_expr;
case_label_t *c_case_labels; /* list of case values */
struct memory_block *c_for_expr3_mem; /* saved memory for end of loop
