Module Name: src
Committed By: rillig
Date: Sat Aug 21 07:52:07 UTC 2021
Modified Files:
src/tests/usr.bin/xlint/lint1: msg_129.c msg_129.exp
Log Message:
tests/lint: demonstrate wrong warnings for 'null effect' expressions
To generate a diff of this commit:
cvs rdiff -u -r1.3 -r1.4 src/tests/usr.bin/xlint/lint1/msg_129.c \
src/tests/usr.bin/xlint/lint1/msg_129.exp
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/msg_129.c
diff -u src/tests/usr.bin/xlint/lint1/msg_129.c:1.3 src/tests/usr.bin/xlint/lint1/msg_129.c:1.4
--- src/tests/usr.bin/xlint/lint1/msg_129.c:1.3 Sat Jan 30 23:05:08 2021
+++ src/tests/usr.bin/xlint/lint1/msg_129.c Sat Aug 21 07:52:07 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: msg_129.c,v 1.3 2021/01/30 23:05:08 rillig Exp $ */
+/* $NetBSD: msg_129.c,v 1.4 2021/08/21 07:52:07 rillig Exp $ */
# 3 "msg_129.c"
// Test for message: expression has null effect [129]
@@ -15,8 +15,8 @@ _Bool side_effect(void);
* wrongly reported as having no side effect.
*
* The bug was that has_side_effect did not properly examine the sub-nodes.
- * The ',' operator has m_has_side_effect == false since it depends on its
- * operands whether the ',' actually has side effects. For nested ','
+ * The ',' operator itself has m_has_side_effect == false since it depends
+ * on its operands whether the ',' actually has side effects. For nested ','
* operators, the function did not evaluate the operands deeply but only did
* a quick shallow test on the m_has_side_effect property. Since that is
* false, lint thought that the whole expression would have no side effect.
@@ -41,3 +41,49 @@ operator_comma(void)
if (0, side_effect()) /* expect: 129 */
return;
}
+
+void
+legitimate_use_cases(int arg)
+{
+ int local = 3;
+
+ /*
+ * This expression is commonly used to mark the argument as
+ * deliberately unused.
+ */
+ /* TODO: remove this bogus warning. */
+ /* expect+1: warning: expression has null effect [129] */
+ (void)arg;
+
+ /*
+ * This expression is commonly used to mark the local variable as
+ * deliberately unused. This situation occurs when the local
+ * variable is only used in some but not all compile-time selectable
+ * variants of the code, such as in debugging mode, and writing down
+ * the exact conditions would complicate the code unnecessarily.
+ */
+ /* TODO: remove this bogus warning. */
+ /* expect+1: warning: expression has null effect [129] */
+ (void)local;
+
+ /* This is a short-hand notation for a do-nothing command. */
+ /* TODO: remove this bogus warning. */
+ /* expect+1: warning: expression has null effect [129] */
+ (void)0;
+
+ /*
+ * This variant of the do-nothing command is commonly used in
+ * preprocessor macros since it works nicely with if-else and if-then
+ * statements. It is longer than the above variant though.
+ */
+ do {
+ } while (0);
+
+ /*
+ * Only the expression '(void)0' is common, other expressions are
+ * unusual enough that they warrant a warning.
+ */
+ /* TODO: remove this bogus warning. */
+ /* expect+1: warning: expression has null effect [129] */
+ (void)13;
+}
Index: src/tests/usr.bin/xlint/lint1/msg_129.exp
diff -u src/tests/usr.bin/xlint/lint1/msg_129.exp:1.3 src/tests/usr.bin/xlint/lint1/msg_129.exp:1.4
--- src/tests/usr.bin/xlint/lint1/msg_129.exp:1.3 Sat Jan 30 23:05:08 2021
+++ src/tests/usr.bin/xlint/lint1/msg_129.exp Sat Aug 21 07:52:07 2021
@@ -1,2 +1,6 @@
msg_129.c(37): warning: expression has null effect [129]
msg_129.c(41): warning: expression has null effect [129]
+msg_129.c(56): warning: expression has null effect [129]
+msg_129.c(67): warning: expression has null effect [129]
+msg_129.c(72): warning: expression has null effect [129]
+msg_129.c(88): warning: expression has null effect [129]
