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'.
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rillig
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@ -1,4 +1,4 @@
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# $NetBSD: mi,v 1.1108 2021/08/08 00:02:02 rillig Exp $
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# $NetBSD: mi,v 1.1109 2021/08/09 20:07:23 rillig Exp $
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#
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# Note: don't delete entries from here - mark them as "obsolete" instead.
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#
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@ -7004,6 +7004,8 @@
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./usr/tests/usr.bin/xlint/lint1/msg_344.exp tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/msg_345.c tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/msg_345.exp tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/msg_346.c tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/msg_346.exp tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/op_colon.c tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/op_colon.exp tests-usr.bin-tests compattestfile,atf
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./usr/tests/usr.bin/xlint/lint1/op_shl_lp64.c tests-usr.bin-tests compattestfile,atf
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@ -1,7 +1,7 @@
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# $NetBSD: Makefile,v 1.102 2021/08/05 06:34:43 rillig Exp $
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# $NetBSD: Makefile,v 1.103 2021/08/09 20:07:24 rillig Exp $
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NOMAN= # defined
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MAX_MESSAGE= 345 # see lint1/err.c
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MAX_MESSAGE= 346 # see lint1/err.c
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.include <bsd.own.mk>
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@ -0,0 +1,32 @@
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/* $NetBSD: msg_346.c,v 1.1 2021/08/09 20:07:24 rillig Exp $ */
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# 3 "msg_346.c"
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// Test for message: call to '%s' effectively discards 'const' from argument [346]
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char *strchr(const char *, int);
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void take_const_char_ptr(const char *);
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void take_char_ptr(char *);
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void
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example(void)
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{
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const char *ccp = "const char *";
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char *cp = "char *";
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ccp = strchr(ccp, 'c');
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ccp = strchr(cp, 'c');
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/* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
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cp = strchr(ccp, 'c');
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cp = strchr(cp, 'c');
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take_const_char_ptr(strchr(ccp, 'c'));
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take_const_char_ptr(strchr(cp, 'c'));
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/* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
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take_char_ptr(strchr(ccp, 'c'));
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take_char_ptr(strchr(cp, 'c'));
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take_const_char_ptr(strchr("literal", 'c'));
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/* expect+1: warning: call to 'strchr' effectively discards 'const' from argument [346] */
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take_char_ptr(strchr("literal", 'c'));
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}
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@ -0,0 +1,3 @@
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msg_346.c(20): warning: call to 'strchr' effectively discards 'const' from argument [346]
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msg_346.c(26): warning: call to 'strchr' effectively discards 'const' from argument [346]
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msg_346.c(31): warning: call to 'strchr' effectively discards 'const' from argument [346]
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@ -1,4 +1,4 @@
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/* $NetBSD: err.c,v 1.134 2021/08/03 20:57:06 rillig Exp $ */
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/* $NetBSD: err.c,v 1.135 2021/08/09 20:07:23 rillig Exp $ */
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/*
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* Copyright (c) 1994, 1995 Jochen Pohl
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@ -37,7 +37,7 @@
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#include <sys/cdefs.h>
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#if defined(__RCSID) && !defined(lint)
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__RCSID("$NetBSD: err.c,v 1.134 2021/08/03 20:57:06 rillig Exp $");
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__RCSID("$NetBSD: err.c,v 1.135 2021/08/09 20:07:23 rillig Exp $");
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#endif
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#include <sys/types.h>
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@ -400,6 +400,7 @@ const char *const msgs[] = {
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"static array size is a C11 extension", /* 343 */
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"bit-field of type plain 'int' has implementation-defined signedness", /* 344 */
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"generic selection requires C11 or later", /* 345 */
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"call to '%s' effectively discards 'const' from argument", /* 346 */
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};
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static struct include_level {
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@ -1,4 +1,4 @@
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/* $NetBSD: tree.c,v 1.330 2021/08/03 21:09:26 rillig Exp $ */
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/* $NetBSD: tree.c,v 1.331 2021/08/09 20:07:23 rillig Exp $ */
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/*
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* Copyright (c) 1994, 1995 Jochen Pohl
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@ -37,7 +37,7 @@
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#include <sys/cdefs.h>
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#if defined(__RCSID) && !defined(lint)
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__RCSID("$NetBSD: tree.c,v 1.330 2021/08/03 21:09:26 rillig Exp $");
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__RCSID("$NetBSD: tree.c,v 1.331 2021/08/09 20:07:23 rillig Exp $");
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#endif
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#include <float.h>
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@ -1346,6 +1346,63 @@ check_pointer_comparison(op_t op, const tnode_t *ln, const tnode_t *rn)
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}
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}
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static bool
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is_direct_function_call(const tnode_t *tn, const char *name)
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{
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return tn->tn_op == CALL &&
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tn->tn_left->tn_op == ADDR &&
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tn->tn_left->tn_left->tn_op == NAME &&
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strcmp(tn->tn_left->tn_left->tn_sym->s_name, name) == 0;
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}
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static bool
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is_const_char_pointer(const tnode_t *tn)
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{
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const type_t *tp;
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/*
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* For traditional reasons, C99 6.4.5p5 defines that string literals
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* have type 'char[]'. They are often implicitly converted to
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* 'char *', for example when they are passed as function arguments.
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*
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* C99 6.4.5p6 further defines that modifying a string that is
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* constructed from a string literal invokes undefined behavior.
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*
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* Out of these reasons, string literals are treated as 'effectively
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* const' here.
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*/
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if (tn->tn_op == CVT &&
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tn->tn_left->tn_op == ADDR &&
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tn->tn_left->tn_left->tn_op == STRING)
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return true;
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tp = before_conversion(tn)->tn_type;
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return tp->t_tspec == PTR &&
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tp->t_subt->t_tspec == CHAR &&
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tp->t_subt->t_const;
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}
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static bool
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is_strchr_arg_const(const tnode_t *tn)
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{
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return tn->tn_right->tn_op == PUSH &&
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tn->tn_right->tn_right->tn_op == PUSH &&
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tn->tn_right->tn_right->tn_right == NULL &&
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is_const_char_pointer(tn->tn_right->tn_right->tn_left);
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}
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static void
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check_unconst_strchr(const type_t *lstp,
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const tnode_t *rn, const type_t *rstp)
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{
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if (lstp->t_tspec == CHAR && !lstp->t_const &&
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is_direct_function_call(rn, "strchr") &&
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is_strchr_arg_const(rn)) {
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/* call to '%s' effectively discards 'const' from argument */
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warning(346, "strchr");
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}
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}
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/*
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* Checks type compatibility for ASSIGN, INIT, FARG and RETURN
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* and prints warnings/errors if necessary.
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break;
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}
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}
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if (!tflag)
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check_unconst_strchr(lstp, rn, rstp);
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return true;
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}
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