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[src/trunk]: src/usr.bin/xlint/lint1 lint: warn about 'char * = strchr(const ...
details: https://anonhg.NetBSD.org/src/rev/499096cb533f
branches: trunk
changeset: 1022852:499096cb533f
user: rillig <rillig%NetBSD.org@localhost>
date: Mon Aug 09 20:07:23 2021 +0000
description:
lint: warn about 'char * = strchr(const char *, int)'
Found in findcc.c, there are about 25 other instances of this
incongruency in the whole source tree.
For more examples of functions from the C Standard Library that
implicitly remove the 'const' qualifier from an argument, see the C++
include file 'cstring'.
diffstat:
distrib/sets/lists/tests/mi | 4 +-
tests/usr.bin/xlint/lint1/Makefile | 4 +-
tests/usr.bin/xlint/lint1/msg_346.c | 32 +++++++++++++++++
tests/usr.bin/xlint/lint1/msg_346.exp | 3 +
usr.bin/xlint/lint1/err.c | 5 +-
usr.bin/xlint/lint1/tree.c | 65 +++++++++++++++++++++++++++++++++-
6 files changed, 106 insertions(+), 7 deletions(-)
diffs (193 lines):
diff -r 3b7cf6b26a0e -r 499096cb533f distrib/sets/lists/tests/mi
--- a/distrib/sets/lists/tests/mi Mon Aug 09 19:57:57 2021 +0000
+++ b/distrib/sets/lists/tests/mi Mon Aug 09 20:07:23 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.1108 2021/08/08 00:02:02 rillig Exp $
+# $NetBSD: mi,v 1.1109 2021/08/09 20:07:23 rillig Exp $
#
# Note: don't delete entries from here - mark them as "obsolete" instead.
#
@@ -7004,6 +7004,8 @@
./usr/tests/usr.bin/xlint/lint1/msg_344.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_345.c tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_345.exp tests-usr.bin-tests compattestfile,atf
+./usr/tests/usr.bin/xlint/lint1/msg_346.c tests-usr.bin-tests compattestfile,atf
+./usr/tests/usr.bin/xlint/lint1/msg_346.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/op_colon.c tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/op_colon.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/op_shl_lp64.c tests-usr.bin-tests compattestfile,atf
diff -r 3b7cf6b26a0e -r 499096cb533f tests/usr.bin/xlint/lint1/Makefile
--- a/tests/usr.bin/xlint/lint1/Makefile Mon Aug 09 19:57:57 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/Makefile Mon Aug 09 20:07:23 2021 +0000
@@ -1,7 +1,7 @@
-# $NetBSD: Makefile,v 1.102 2021/08/05 06:34:43 rillig Exp $
+# $NetBSD: Makefile,v 1.103 2021/08/09 20:07:24 rillig Exp $
NOMAN= # defined
-MAX_MESSAGE= 345 # see lint1/err.c
+MAX_MESSAGE= 346 # see lint1/err.c
.include <bsd.own.mk>
diff -r 3b7cf6b26a0e -r 499096cb533f tests/usr.bin/xlint/lint1/msg_346.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_346.c Mon Aug 09 20:07:23 2021 +0000
@@ -0,0 +1,32 @@
+/* $NetBSD: msg_346.c,v 1.1 2021/08/09 20:07:24 rillig Exp $ */
+# 3 "msg_346.c"
+
+// Test for message: call to '%s' effectively discards 'const' from argument [346]
+
+char *strchr(const char *, int);
+
+void take_const_char_ptr(const char *);
+void take_char_ptr(char *);
+
+void
+example(void)
+{
+ const char *ccp = "const char *";
+ char *cp = "char *";
+
+ ccp = strchr(ccp, 'c');
+ ccp = strchr(cp, 'c');
+ /* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
+ cp = strchr(ccp, 'c');
+ cp = strchr(cp, 'c');
+
+ take_const_char_ptr(strchr(ccp, 'c'));
+ take_const_char_ptr(strchr(cp, 'c'));
+ /* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
+ take_char_ptr(strchr(ccp, 'c'));
+ take_char_ptr(strchr(cp, 'c'));
+
+ take_const_char_ptr(strchr("literal", 'c'));
+ /* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
+ take_char_ptr(strchr("literal", 'c'));
+}
diff -r 3b7cf6b26a0e -r 499096cb533f tests/usr.bin/xlint/lint1/msg_346.exp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_346.exp Mon Aug 09 20:07:23 2021 +0000
@@ -0,0 +1,3 @@
+msg_346.c(20): warning: call to 'strchr' effectively discards 'const' from argument [346]
+msg_346.c(26): warning: call to 'strchr' effectively discards 'const' from argument [346]
+msg_346.c(31): warning: call to 'strchr' effectively discards 'const' from argument [346]
diff -r 3b7cf6b26a0e -r 499096cb533f usr.bin/xlint/lint1/err.c
--- a/usr.bin/xlint/lint1/err.c Mon Aug 09 19:57:57 2021 +0000
+++ b/usr.bin/xlint/lint1/err.c Mon Aug 09 20:07:23 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: err.c,v 1.134 2021/08/03 20:57:06 rillig Exp $ */
+/* $NetBSD: err.c,v 1.135 2021/08/09 20:07:23 rillig Exp $ */
/*
* Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
#include <sys/cdefs.h>
#if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: err.c,v 1.134 2021/08/03 20:57:06 rillig Exp $");
+__RCSID("$NetBSD: err.c,v 1.135 2021/08/09 20:07:23 rillig Exp $");
#endif
#include <sys/types.h>
@@ -400,6 +400,7 @@
"static array size is a C11 extension", /* 343 */
"bit-field of type plain 'int' has implementation-defined signedness", /* 344 */
"generic selection requires C11 or later", /* 345 */
+ "call to '%s' effectively discards 'const' from argument", /* 346 */
};
static struct include_level {
diff -r 3b7cf6b26a0e -r 499096cb533f usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c Mon Aug 09 19:57:57 2021 +0000
+++ b/usr.bin/xlint/lint1/tree.c Mon Aug 09 20:07:23 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: tree.c,v 1.330 2021/08/03 21:09:26 rillig Exp $ */
+/* $NetBSD: tree.c,v 1.331 2021/08/09 20:07:23 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 1.330 2021/08/03 21:09:26 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.331 2021/08/09 20:07:23 rillig Exp $");
#endif
#include <float.h>
@@ -1346,6 +1346,63 @@
}
}
+static bool
+is_direct_function_call(const tnode_t *tn, const char *name)
+{
+ return tn->tn_op == CALL &&
+ tn->tn_left->tn_op == ADDR &&
+ tn->tn_left->tn_left->tn_op == NAME &&
+ strcmp(tn->tn_left->tn_left->tn_sym->s_name, name) == 0;
+}
+
+static bool
+is_const_char_pointer(const tnode_t *tn)
+{
+ const type_t *tp;
+
+ /*
+ * For traditional reasons, C99 6.4.5p5 defines that string literals
+ * have type 'char[]'. They are often implicitly converted to
+ * 'char *', for example when they are passed as function arguments.
+ *
+ * C99 6.4.5p6 further defines that modifying a string that is
+ * constructed from a string literal invokes undefined behavior.
+ *
+ * Out of these reasons, string literals are treated as 'effectively
+ * const' here.
+ */
+ if (tn->tn_op == CVT &&
+ tn->tn_left->tn_op == ADDR &&
+ tn->tn_left->tn_left->tn_op == STRING)
+ return true;
+
+ tp = before_conversion(tn)->tn_type;
+ return tp->t_tspec == PTR &&
+ tp->t_subt->t_tspec == CHAR &&
+ tp->t_subt->t_const;
+}
+
+static bool
+is_strchr_arg_const(const tnode_t *tn)
+{
+ return tn->tn_right->tn_op == PUSH &&
+ tn->tn_right->tn_right->tn_op == PUSH &&
+ tn->tn_right->tn_right->tn_right == NULL &&
+ is_const_char_pointer(tn->tn_right->tn_right->tn_left);
+}
+
+static void
+check_unconst_strchr(const type_t *lstp,
+ const tnode_t *rn, const type_t *rstp)
+{
+ if (lstp->t_tspec == CHAR && !lstp->t_const &&
+ is_direct_function_call(rn, "strchr") &&
+ is_strchr_arg_const(rn)) {
+ /* call to '%s' effectively discards 'const' from argument */
+ warning(346, "strchr");
+ }
+}
+
/*
* Checks type compatibility for ASSIGN, INIT, FARG and RETURN
* and prints warnings/errors if necessary.
@@ -1429,6 +1486,10 @@
break;
}
}
+
+ if (!tflag)
+ check_unconst_strchr(lstp, rn, rstp);
+
return true;
}
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