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lint: warn about for wrong type cast in argument to ctype.h functions

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The argument to most of the functions from <ctype.h> "shall either be
representable as an 'unsigned char' or shall equal the value of the
macro EOF".

When confronted with the infamous warning 'array subscript has type
char', there are enough programmers who don't know the background of
that warning and thus fix it in a wrong way.  Neither GCC nor Clang
explain its warning to target these programmers.

Both GCC and Clang warn about 'array subscript has type char', but they
ignore the other requirements of the <ctype.h> functions, even though
these are in the C standard library.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94182
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95177
https://stackoverflow.com/a/60696378
This commit is contained in:
rillig 2021-04-05 02:05:47 +00:00
parent 5bbf966f2d
commit b5bd70af56
12 changed files with 349 additions and 13 deletions
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6
distrib/sets/lists/tests/mi
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@ -1,4 +1,4 @@
# $NetBSD: mi,v 1.1036 2021/04/04 13:20:52 rillig Exp $
# $NetBSD: mi,v 1.1037 2021/04/05 02:05:47 rillig Exp $
#
# Note: don't delete entries from here - mark them as "obsolete" instead.
#
@ -6863,6 +6863,10 @@
./usr/tests/usr.bin/xlint/lint1/msg_339.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_340.c tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_340.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_341.c tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_341.exp tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_342.c tests-usr.bin-tests compattestfile,atf
./usr/tests/usr.bin/xlint/lint1/msg_342.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/t_integration tests-usr.bin-tests compattestfile,atf

5
tests/usr.bin/xlint/lint1/Makefile
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@ -1,6 +1,7 @@
# $NetBSD: Makefile,v 1.38 2021/04/02 17:25:04 rillig Exp $
# $NetBSD: Makefile,v 1.39 2021/04/05 02:05:47 rillig Exp $
NOMAN= # defined
MAX_MESSAGE= 342 # see lint1/err.c
.include <bsd.own.mk>
@ -98,7 +99,7 @@ FILES+= d_type_question_colon.c
FILES+= d_typefun.c
FILES+= d_typename_as_var.c
FILES+= d_zero_sized_arrays.c
FILES+= ${:U0 ${:U:range=340}:C,^.$,0&,:C,^..$,0&,:@msg@msg_${msg}.c msg_${msg}.exp@:Nmsg_176.exp}
FILES+= ${:U0 ${:U:${:Urange=${MAX_MESSAGE}}}:C,^.$,0&,:C,^..$,0&,:@i@msg_${i}.c msg_${i}.exp@:Nmsg_176.exp}
FILES+= op_colon.c
FILES+= op_colon.exp

77
tests/usr.bin/xlint/lint1/msg_341.c Normal file
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@ -0,0 +1,77 @@
/* $NetBSD: msg_341.c,v 1.1 2021/04/05 02:05:47 rillig Exp $ */
# 3 "msg_341.c"
// Test for message: argument to '%s' must be 'unsigned char' or EOF, not '%s' [341]
/*
* Ensure that the functions from <ctype.h> are called with the correct
* argument.
*/
/* NetBSD 9.99.81, <ctype.h> */
extern const unsigned short *_ctype_tab_;
extern const short *_tolower_tab_;
extern const short *_toupper_tab_;
int isspace(int);
void sink(int);
void
function_call_char(char c)
{
/* expect+1: argument to 'isspace' must be 'unsigned char' or EOF, not 'char' */
(isspace)(c);
/* This is the only allowed form. */
isspace((unsigned char)c);
/* The cast to 'int' is redundant, it doesn't hurt though. */
isspace((int)(unsigned char)c);
/* expect+1: argument to 'isspace' must be cast to 'unsigned char', not to 'int' */
isspace((int)c);
/* expect+1: argument to 'isspace' must be cast to 'unsigned char', not to 'unsigned int' */
isspace((unsigned int)c);
}
/*
* If the expression starts with type 'unsigned char', it can be cast to any
* other type. Chances are low enough that the cast is to 'char', which would
* be the only bad type.
*/
void
function_call_unsigned_char(unsigned char c)
{
(isspace)(c);
isspace((unsigned char)c);
isspace((int)c);
isspace((unsigned int)c);
}
/* When used in a loop of fgetc, the type is already 'int'. That's fine. */
void
function_call_int(int c)
{
isspace(c);
}
void
macro_invocation_NetBSD(char c)
{
/* expect+1: argument to 'function from <ctype.h>' must be 'unsigned char' or EOF, not 'char' */
sink(((int)((_ctype_tab_ + 1)[(c)] & 0x0040)));
/* This is the only allowed form. */
sink(((int)((_ctype_tab_ + 1)[((unsigned char)c)] & 0x0040)));
/* expect+1: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'int' */
sink(((int)((_ctype_tab_ + 1)[((int)c)] & 0x0040)));
/* expect+1: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'unsigned int' */
sink(((int)((_ctype_tab_ + 1)[((unsigned int)c)] & 0x0040)));
}

6
tests/usr.bin/xlint/lint1/msg_341.exp Normal file
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@ -0,0 +1,6 @@
msg_341.c(24): warning: argument to 'isspace' must be 'unsigned char' or EOF, not 'char' [341]
msg_341.c(33): warning: argument to 'isspace' must be cast to 'unsigned char', not to 'int' [342]
msg_341.c(36): warning: argument to 'isspace' must be cast to 'unsigned char', not to 'unsigned int' [342]
msg_341.c(67): warning: argument to 'function from <ctype.h>' must be 'unsigned char' or EOF, not 'char' [341]
msg_341.c(73): warning: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'int' [342]
msg_341.c(76): warning: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'unsigned int' [342]

77
tests/usr.bin/xlint/lint1/msg_342.c Normal file
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@ -0,0 +1,77 @@
/* $NetBSD: msg_342.c,v 1.1 2021/04/05 02:05:47 rillig Exp $ */
# 3 "msg_341.c"
// Test for message: argument to '%s' must be cast to 'unsigned char', not to '%s' [342]
/*
* Ensure that the functions from <ctype.h> are called with the correct
* argument.
*/
/* NetBSD 9.99.81, <ctype.h> */
extern const unsigned short *_ctype_tab_;
extern const short *_tolower_tab_;
extern const short *_toupper_tab_;
int isspace(int);
void sink(int);
void
function_call_char(char c)
{
/* expect+1: argument to 'isspace' must be 'unsigned char' or EOF, not 'char' */
(isspace)(c);
/* This is the only allowed form. */
isspace((unsigned char)c);
/* The cast to 'int' is redundant, it doesn't hurt though. */
isspace((int)(unsigned char)c);
/* expect+1: argument to 'isspace' must be cast to 'unsigned char', not to 'int' */
isspace((int)c);
/* expect+1: argument to 'isspace' must be cast to 'unsigned char', not to 'unsigned int' */
isspace((unsigned int)c);
}
/*
* If the expression starts with type 'unsigned char', it can be cast to any
* other type. Chances are low enough that the cast is to 'char', which would
* be the only bad type.
*/
void
function_call_unsigned_char(unsigned char c)
{
(isspace)(c);
isspace((unsigned char)c);
isspace((int)c);
isspace((unsigned int)c);
}
/* When used in a loop of fgetc, the type is already 'int'. That's fine. */
void
function_call_int(int c)
{
isspace(c);
}
void
macro_invocation_NetBSD(char c)
{
/* expect+1: argument to 'function from <ctype.h>' must be 'unsigned char' or EOF, not 'char' */
sink(((int)((_ctype_tab_ + 1)[(c)] & 0x0040)));
/* This is the only allowed form. */
sink(((int)((_ctype_tab_ + 1)[((unsigned char)c)] & 0x0040)));
/* expect+1: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'int' */
sink(((int)((_ctype_tab_ + 1)[((int)c)] & 0x0040)));
/* expect+1: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'unsigned int' */
sink(((int)((_ctype_tab_ + 1)[((unsigned int)c)] & 0x0040)));
}

6
tests/usr.bin/xlint/lint1/msg_342.exp Normal file
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@ -0,0 +1,6 @@
msg_341.c(24): warning: argument to 'isspace' must be 'unsigned char' or EOF, not 'char' [341]
msg_341.c(33): warning: argument to 'isspace' must be cast to 'unsigned char', not to 'int' [342]
msg_341.c(36): warning: argument to 'isspace' must be cast to 'unsigned char', not to 'unsigned int' [342]
msg_341.c(67): warning: argument to 'function from <ctype.h>' must be 'unsigned char' or EOF, not 'char' [341]
msg_341.c(73): warning: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'int' [342]
msg_341.c(76): warning: argument to 'function from <ctype.h>' must be cast to 'unsigned char', not to 'unsigned int' [342]

4
tests/usr.bin/xlint/lint1/t_integration.sh
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@ -1,4 +1,4 @@
# $NetBSD: t_integration.sh,v 1.38 2021/04/02 17:25:04 rillig Exp $
# $NetBSD: t_integration.sh,v 1.39 2021/04/05 02:05:47 rillig Exp $
#
# Copyright (c) 2008, 2010 The NetBSD Foundation, Inc.
# All rights reserved.
@ -175,7 +175,7 @@ all_messages_body()
failed=""
for msg in $(seq 0 340); do
for msg in $(seq 0 342); do
name="$(printf 'msg_%03d.c' "${msg}")"
check_lint1 "${name}" \
|| failed="$failed${failed:+ }$name"

4
usr.bin/xlint/lint1/Makefile
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@ -1,9 +1,9 @@
# $NetBSD: Makefile,v 1.64 2021/03/21 13:10:58 rillig Exp $
# $NetBSD: Makefile,v 1.65 2021/04/05 02:05:47 rillig Exp $
.include <bsd.own.mk>
PROG= lint1
SRCS= cgram.y ckgetopt.c decl.c emit.c emit1.c err.c \
SRCS= cgram.y ckctype.c ckgetopt.c decl.c emit.c emit1.c err.c \
func.c init.c inittyp.c lex.c \
main1.c mem.c mem1.c oper.c print.c scan.l tree.c tyname.c

151
usr.bin/xlint/lint1/ckctype.c Normal file
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@ -0,0 +1,151 @@
/* $NetBSD: ckctype.c,v 1.1 2021/04/05 02:07:14 rillig Exp $ */
/*-
* Copyright (c) 2021 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Roland Illig <rillig@NetBSD.org>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif
#include <sys/cdefs.h>
#if defined(__RCSID) && !defined(lint)
__RCSID("$NetBSD: ckctype.c,v 1.1 2021/04/05 02:07:14 rillig Exp $");
#endif
#include <string.h>
#include "lint1.h"
/*
* Check that the functions from <ctype.h> are used properly. They are
* difficult to use when their argument comes from an expression of type
* 'char'. In such a case, the argument must be converted to 'unsigned char',
* not directly to 'int'.
*
* https://stackoverflow.com/a/60696378
*/
#define NEED(cond) \
do { \
if (!(cond)) \
return; \
} while (false)
static bool
is_ctype_function(const char *name)
{
if (name[0] != 'i' || name[1] != 's')
if (name[0] != 't' || name[1] != 'o')
return false;
return strcmp(name, "isalnum") == 0 ||
strcmp(name, "isalpha") == 0 ||
strcmp(name, "isblank") == 0 ||
strcmp(name, "iscntrl") == 0 ||
strcmp(name, "isdigit") == 0 ||
strcmp(name, "isgraph") == 0 ||
strcmp(name, "islower") == 0 ||
strcmp(name, "isprint") == 0 ||
strcmp(name, "ispunct") == 0 ||
strcmp(name, "isspace") == 0 ||
strcmp(name, "isupper") == 0 ||
strcmp(name, "isxdigit") == 0 ||
strcmp(name, "tolower") == 0 ||
strcmp(name, "toupper") == 0;
}
static bool
is_ctype_table(const char *name)
{
/* NetBSD sys/ctype_bits.h 1.6 from 2016-01-22 */
if (strcmp(name, "_ctype_tab_") == 0 ||
strcmp(name, "_tolower_tab_") == 0 ||
strcmp(name, "_toupper_tab_") == 0)
return true;
/* NetBSD sys/ctype_bits.h 1.1 from 2010-06-01 */
return strcmp(name, "_ctype_") == 0;
}
static void
check_ctype_arg(const char *func, const tnode_t *arg)
{
const tnode_t *on, *cn;
for (on = arg; on->tn_op == CVT; on = on->tn_left)
if (on->tn_type->t_tspec == UCHAR)
return;
if (on->tn_type->t_tspec == UCHAR)
return;
if (arg->tn_op == CVT && arg->tn_cast) {
/* argument to '%s' must be cast to 'unsigned char', not to '%s' */
warning(342, func, type_name(arg->tn_type));
return;
}
cn = before_conversion(arg);
if (cn->tn_type->t_tspec == CHAR) {
/* argument to '%s' must be 'unsigned char' or EOF, not '%s' */
warning(341, func, type_name(cn->tn_type));
return;
}
}
void
check_ctype_function_call(const tnode_t *func, const tnode_t *args)
{
NEED(func->tn_op == NAME);
NEED(is_ctype_function(func->tn_sym->s_name));
NEED(args != NULL);
NEED(args->tn_left != NULL);
NEED(args->tn_right == NULL);
check_ctype_arg(func->tn_sym->s_name, args->tn_left);
}
void
check_ctype_macro_invocation(const tnode_t *ln, const tnode_t *rn)
{
NEED(ln->tn_op == PLUS);
NEED(ln->tn_left != NULL);
NEED(ln->tn_left->tn_op == LOAD);
NEED(ln->tn_left->tn_left != NULL);
NEED(ln->tn_left->tn_left->tn_op == NAME);
NEED(is_ctype_table(ln->tn_left->tn_left->tn_sym->s_name));
check_ctype_arg("function from <ctype.h>", rn);
}

6
usr.bin/xlint/lint1/err.c
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@ -1,4 +1,4 @@
/* $NetBSD: err.c,v 1.101 2021/04/02 22:41:53 rillig Exp $ */
/* $NetBSD: err.c,v 1.102 2021/04/05 02:05:47 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 1.101 2021/04/02 22:41:53 rillig Exp $");
__RCSID("$NetBSD: err.c,v 1.102 2021/04/05 02:05:47 rillig Exp $");
#endif
#include <sys/types.h>
@ -395,6 +395,8 @@ const char *msgs[] = {
"option '%c' should be handled in the switch", /* 338 */
"option '%c' should be listed in the options string", /* 339 */
"initialization with '[a...b]' is a GNU extension", /* 340 */
"argument to '%s' must be 'unsigned char' or EOF, not '%s'", /* 341 */
"argument to '%s' must be cast to 'unsigned char', not to '%s'", /* 342 */
};
/*

9
usr.bin/xlint/lint1/externs1.h
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@ -1,4 +1,4 @@
/* $NetBSD: externs1.h,v 1.99 2021/04/02 11:53:25 rillig Exp $ */
/* $NetBSD: externs1.h,v 1.100 2021/04/05 02:05:47 rillig Exp $ */
/*
* Copyright (c) 1994, 1995 Jochen Pohl
@ -196,6 +196,7 @@ extern int to_int_constant(tnode_t *, bool);
/*
* tree.c
*/
extern const tnode_t *before_conversion(const tnode_t *);
extern type_t *derive_type(type_t *, tspec_t);
extern type_t *expr_derive_type(type_t *, tspec_t);
extern tnode_t *expr_new_constant(type_t *, val_t *);
@ -334,6 +335,12 @@ extern int lex_input(void);
*/
extern char *print_tnode(char *, size_t, const tnode_t *);
/*
* ckctype.c
*/
extern void check_ctype_function_call(const tnode_t *, const tnode_t *);
extern void check_ctype_macro_invocation(const tnode_t *, const tnode_t *);
/*
* ckgetopt.c
*/

11
usr.bin/xlint/lint1/tree.c
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@ -1,4 +1,4 @@
/* $NetBSD: tree.c,v 1.265 2021/04/02 22:41:53 rillig Exp $ */
/* $NetBSD: tree.c,v 1.266 2021/04/05 02:05:47 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 1.265 2021/04/02 22:41:53 rillig Exp $");
__RCSID("$NetBSD: tree.c,v 1.266 2021/04/05 02:05:47 rillig Exp $");
#endif
#include <float.h>
@ -718,7 +718,7 @@ cconv(tnode_t *tn)
return tn;
}
static const tnode_t *
const tnode_t *
before_conversion(const tnode_t *tn)
{
while (tn->tn_op == CVT && !tn->tn_cast)
@ -2800,8 +2800,11 @@ build_plus_minus(op_t op, tnode_t *ln, tnode_t *rn)
if (ln->tn_type->t_tspec == PTR && rn->tn_type->t_tspec != PTR) {
/* XXX: this assertion should be easy to trigger */
lint_assert(is_integer(rn->tn_type->t_tspec));
check_ctype_macro_invocation(ln, rn);
ctn = plength(ln->tn_type);
if (rn->tn_type->t_tspec != ctn->tn_type->t_tspec)
rn = convert(NOOP, 0, ctn->tn_type, rn);
@ -3585,6 +3588,8 @@ new_function_call_node(tnode_t *func, tnode_t *args)
fcop = ICALL;
}
check_ctype_function_call(func, args);
/*
* after cconv() func will always be a pointer to a function
* if it is a valid function designator.