forked from danmar/cppcheck
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathcheckstring.cpp
More file actions
363 lines (319 loc) · 16.7 KB
/
checkstring.cpp
File metadata and controls
363 lines (319 loc) · 16.7 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2015 Daniel Marjamäki and Cppcheck team.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
#include "checkstring.h"
#include "symboldatabase.h"
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckString instance;
}
//---------------------------------------------------------------------------
// Writing string literal is UB
//---------------------------------------------------------------------------
void CheckString::stringLiteralWrite()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (!tok->variable() || !tok->variable()->isPointer())
continue;
const Token *str = tok->getValueTokenMinStrSize();
if (!str)
continue;
if (Token::Match(tok, "%var% [") && Token::simpleMatch(tok->linkAt(1), "] ="))
stringLiteralWriteError(tok, str);
else if (Token::Match(tok->previous(), "* %var% ="))
stringLiteralWriteError(tok, str);
}
}
}
void CheckString::stringLiteralWriteError(const Token *tok, const Token *strValue)
{
std::list<const Token *> callstack;
callstack.push_back(tok);
if (strValue)
callstack.push_back(strValue);
std::string errmsg("Modifying string literal");
if (strValue) {
std::string s = strValue->strValue();
if (s.size() > 15U)
s = s.substr(0,13) + "..";
errmsg += " \"" + s + "\"";
}
errmsg += " directly or indirectly is undefined behaviour.";
reportError(callstack, Severity::error, "stringLiteralWrite", errmsg);
}
//---------------------------------------------------------------------------
// Check for string comparison involving two static strings.
// if(strcmp("00FF00","00FF00")==0) // <- statement is always true
//---------------------------------------------------------------------------
void CheckString::checkAlwaysTrueOrFalseStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
for (const Token* tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (tok->isName() && Token::Match(tok, "memcmp|strncmp|strcmp|stricmp|strverscmp|bcmp|strcmpi|strcasecmp|strncasecmp|strncasecmp_l|strcasecmp_l|wcsncasecmp|wcscasecmp|wmemcmp|wcscmp|wcscasecmp_l|wcsncasecmp_l|wcsncmp|_mbscmp|_memicmp|_memicmp_l|_stricmp|_wcsicmp|_mbsicmp|_stricmp_l|_wcsicmp_l|_mbsicmp_l (")) {
if (Token::Match(tok->tokAt(2), "%str% , %str% ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(4);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(5);
} else if (Token::Match(tok->tokAt(2), "%name% , %name% ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(4);
if (str1 == str2)
alwaysTrueStringVariableCompareError(tok, str1, str2);
tok = tok->tokAt(5);
} else if (Token::Match(tok->tokAt(2), "%name% . c_str ( ) , %name% . c_str ( ) ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(8);
if (str1 == str2)
alwaysTrueStringVariableCompareError(tok, str1, str2);
tok = tok->tokAt(13);
}
} else if (tok->isName() && Token::Match(tok, "QString :: compare ( %str% , %str% )")) {
const std::string &str1 = tok->strAt(4);
const std::string &str2 = tok->strAt(6);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(7);
} else if (Token::Match(tok, "!!+ %str% ==|!= %str% !!+")) {
const std::string &str1 = tok->strAt(1);
const std::string &str2 = tok->strAt(3);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(5);
}
if (!tok)
break;
}
}
void CheckString::alwaysTrueFalseStringCompareError(const Token *tok, const std::string& str1, const std::string& str2)
{
const std::size_t stringLen = 10;
const std::string string1 = (str1.size() < stringLen) ? str1 : (str1.substr(0, stringLen-2) + "..");
const std::string string2 = (str2.size() < stringLen) ? str2 : (str2.substr(0, stringLen-2) + "..");
reportError(tok, Severity::warning, "staticStringCompare",
"Unnecessary comparison of static strings.\n"
"The compared strings, '" + string1 + "' and '" + string2 + "', are always " + (str1==str2?"identical":"unequal") + ". "
"Therefore the comparison is unnecessary and looks suspicious.");
}
void CheckString::alwaysTrueStringVariableCompareError(const Token *tok, const std::string& str1, const std::string& str2)
{
reportError(tok, Severity::warning, "stringCompare",
"Comparison of identical string variables.\n"
"The compared strings, '" + str1 + "' and '" + str2 + "', are identical. "
"This could be a logic bug.");
}
//-----------------------------------------------------------------------------
// Detect "str == '\0'" where "*str == '\0'" is correct.
// Comparing char* with each other instead of using strcmp()
//-----------------------------------------------------------------------------
void CheckString::checkSuspiciousStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (tok->tokType() != Token::eComparisonOp)
continue;
const Token* varTok = tok->astOperand1();
const Token* litTok = tok->astOperand2();
if (!varTok || !litTok) // <- failed to create AST for comparison
continue;
if (varTok->tokType() == Token::eString || varTok->tokType() == Token::eNumber)
std::swap(varTok, litTok);
else if (litTok->tokType() != Token::eString && litTok->tokType() != Token::eNumber)
continue;
// Pointer addition?
if (varTok->str() == "+" && _tokenizer->isC()) {
const Token *tokens[2] = { varTok->astOperand1(), varTok->astOperand2() };
for (int nr = 0; nr < 2; nr++) {
const Token *t = tokens[nr];
while (t && (t->str() == "." || t->str() == "::"))
t = t->astOperand2();
if (t && t->variable() && t->variable()->isPointer())
varTok = t;
}
}
if (varTok->str() == "*") {
if (!_tokenizer->isC() || varTok->astOperand2() != nullptr || litTok->tokType() != Token::eString)
continue;
varTok = varTok->astOperand1();
}
while (varTok && (varTok->str() == "." || varTok->str() == "::"))
varTok = varTok->astOperand2();
if (!varTok || !varTok->isName())
continue;
const Variable *var = varTok->variable();
while (Token::Match(varTok->astParent(), "[.*]"))
varTok = varTok->astParent();
const std::string varname = varTok->expressionString();
if (litTok->tokType() == Token::eString) {
if (_tokenizer->isC() || (var && var->isArrayOrPointer()))
suspiciousStringCompareError(tok, varname);
} else if (litTok->originalName() == "'\\0'" && var && var->isPointer()) {
suspiciousStringCompareError_char(tok, varname);
}
}
}
}
void CheckString::suspiciousStringCompareError(const Token* tok, const std::string& var)
{
reportError(tok, Severity::warning, "literalWithCharPtrCompare",
"String literal compared with variable '" + var + "'. Did you intend to use strcmp() instead?");
}
void CheckString::suspiciousStringCompareError_char(const Token* tok, const std::string& var)
{
reportError(tok, Severity::warning, "charLiteralWithCharPtrCompare",
"Char literal compared with pointer '" + var + "'. Did you intend to dereference it?");
}
//---------------------------------------------------------------------------
// Adding C-string and char with operator+
//---------------------------------------------------------------------------
static bool isChar(const Variable* var)
{
return (var && !var->isPointer() && !var->isArray() && var->typeStartToken()->str() == "char");
}
void CheckString::strPlusChar()
{
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (tok->str() == "+") {
if (tok->astOperand1() && (tok->astOperand1()->tokType() == Token::eString)) { // string literal...
if (tok->astOperand2() && (tok->astOperand2()->tokType() == Token::eChar || isChar(tok->astOperand2()->variable()))) // added to char variable or char constant
strPlusCharError(tok);
}
}
}
}
}
void CheckString::strPlusCharError(const Token *tok)
{
reportError(tok, Severity::error, "strPlusChar", "Unusual pointer arithmetic. A value of type 'char' is added to a string literal.");
}
//---------------------------------------------------------------------------
// Implicit casts of string literals to bool
// Comparing string literal with strlen() with wrong length
//---------------------------------------------------------------------------
void CheckString::checkIncorrectStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
// skip "assert(str && ..)" and "assert(.. && str)"
if (tok->str().size() >= 6U && (tok->str().find("assert") == tok->str().size() - 6U || tok->str().find("ASSERT") == tok->str().size() - 6U) &&
Token::Match(tok, "%name% (") &&
(Token::Match(tok->tokAt(2), "%str% &&") || Token::Match(tok->next()->link()->tokAt(-2), "&& %str% )")))
tok = tok->next()->link();
if (Token::simpleMatch(tok, ". substr (") && Token::Match(tok->tokAt(3)->nextArgument(), "%num% )")) {
MathLib::bigint clen = MathLib::toLongNumber(tok->linkAt(2)->strAt(-1));
const Token* begin = tok->previous();
for (;;) { // Find start of statement
while (begin->link() && Token::Match(begin, "]|)|>"))
begin = begin->link()->previous();
if (Token::Match(begin->previous(), ".|::"))
begin = begin->tokAt(-2);
else
break;
}
begin = begin->previous();
const Token* end = tok->linkAt(2)->next();
if (Token::Match(begin->previous(), "%str% ==|!=") && begin->strAt(-2) != "+") {
std::size_t slen = Token::getStrLength(begin->previous());
if (clen != (int)slen) {
incorrectStringCompareError(tok->next(), "substr", begin->strAt(-1));
}
} else if (Token::Match(end, "==|!= %str% !!+")) {
std::size_t slen = Token::getStrLength(end->next());
if (clen != (int)slen) {
incorrectStringCompareError(tok->next(), "substr", end->strAt(1));
}
}
} else if (Token::Match(tok, "&&|%oror%|( %str% &&|%oror%|)") && !Token::Match(tok, "( %str% )")) {
incorrectStringBooleanError(tok->next(), tok->strAt(1));
} else if (Token::Match(tok, "if|while ( %str% )")) {
incorrectStringBooleanError(tok->tokAt(2), tok->strAt(2));
}
}
}
}
void CheckString::incorrectStringCompareError(const Token *tok, const std::string& func, const std::string &string)
{
reportError(tok, Severity::warning, "incorrectStringCompare", "String literal " + string + " doesn't match length argument for " + func + "().");
}
void CheckString::incorrectStringBooleanError(const Token *tok, const std::string& string)
{
reportError(tok, Severity::warning, "incorrectStringBooleanError", "Conversion of string literal " + string + " to bool always evaluates to true.");
}
//---------------------------------------------------------------------------
// Overlapping source and destination passed to sprintf().
//---------------------------------------------------------------------------
void CheckString::sprintfOverlappingData()
{
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
// Get variable id of target buffer..
unsigned int varid = 0;
if (Token::Match(tok, "sprintf|snprintf|swprintf ( %var% ,"))
varid = tok->tokAt(2)->varId();
else if (Token::Match(tok, "sprintf|snprintf|swprintf ( %name% . %var% ,"))
varid = tok->tokAt(4)->varId();
else
continue;
// goto next argument
const Token *tok2 = tok->tokAt(2)->nextArgument();
if (tok->str() == "snprintf" || tok->str() == "swprintf") { // Jump over second parameter for snprintf and swprintf
tok2 = tok2->nextArgument();
if (!tok2)
continue;
}
// is any source buffer overlapping the target buffer?
do {
if (Token::Match(tok2, "%varid% [,)]", varid)) {
sprintfOverlappingDataError(tok2, tok2->str());
break;
}
} while (nullptr != (tok2 = tok2->nextArgument()));
}
}
}
void CheckString::sprintfOverlappingDataError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::error, "sprintfOverlappingData",
"Undefined behavior: Variable '" + varname + "' is used as parameter and destination in s[n]printf().\n"
"The variable '" + varname + "' is used both as a parameter and as destination in "
"s[n]printf(). The origin and destination buffers overlap. Quote from glibc (C-library) "
"documentation (http://www.gnu.org/software/libc/manual/html_mono/libc.html#Formatted-Output-Functions): "
"\"If copying takes place between objects that overlap as a result of a call "
"to sprintf() or snprintf(), the results are undefined.\"");
}