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
|
//===--- MisplacedWideningCastCheck.cpp - clang-tidy-----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "MisplacedWideningCastCheck.h"
#include "../utils/Matchers.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace bugprone {
MisplacedWideningCastCheck::MisplacedWideningCastCheck(
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
CheckImplicitCasts(Options.get("CheckImplicitCasts", false)) {}
void MisplacedWideningCastCheck::storeOptions(
ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "CheckImplicitCasts", CheckImplicitCasts);
}
void MisplacedWideningCastCheck::registerMatchers(MatchFinder *Finder) {
const auto Calc =
expr(anyOf(binaryOperator(
anyOf(hasOperatorName("+"), hasOperatorName("-"),
hasOperatorName("*"), hasOperatorName("<<"))),
unaryOperator(hasOperatorName("~"))),
hasType(isInteger()))
.bind("Calc");
const auto ExplicitCast = explicitCastExpr(hasDestinationType(isInteger()),
has(ignoringParenImpCasts(Calc)));
const auto ImplicitCast =
implicitCastExpr(hasImplicitDestinationType(isInteger()),
has(ignoringParenImpCasts(Calc)));
const auto Cast = expr(anyOf(ExplicitCast, ImplicitCast)).bind("Cast");
Finder->addMatcher(varDecl(hasInitializer(Cast)), this);
Finder->addMatcher(returnStmt(hasReturnValue(Cast)), this);
Finder->addMatcher(callExpr(hasAnyArgument(Cast)), this);
Finder->addMatcher(binaryOperator(hasOperatorName("="), hasRHS(Cast)), this);
Finder->addMatcher(
binaryOperator(matchers::isComparisonOperator(), hasEitherOperand(Cast)),
this);
}
static unsigned getMaxCalculationWidth(const ASTContext &Context,
const Expr *E) {
E = E->IgnoreParenImpCasts();
if (const auto *Bop = dyn_cast<BinaryOperator>(E)) {
unsigned LHSWidth = getMaxCalculationWidth(Context, Bop->getLHS());
unsigned RHSWidth = getMaxCalculationWidth(Context, Bop->getRHS());
if (Bop->getOpcode() == BO_Mul)
return LHSWidth + RHSWidth;
if (Bop->getOpcode() == BO_Add)
return std::max(LHSWidth, RHSWidth) + 1;
if (Bop->getOpcode() == BO_Rem) {
Expr::EvalResult Result;
if (Bop->getRHS()->EvaluateAsInt(Result, Context))
return Result.Val.getInt().getActiveBits();
} else if (Bop->getOpcode() == BO_Shl) {
Expr::EvalResult Result;
if (Bop->getRHS()->EvaluateAsInt(Result, Context)) {
// We don't handle negative values and large values well. It is assumed
// that compiler warnings are written for such values so the user will
// fix that.
return LHSWidth + Result.Val.getInt().getExtValue();
}
// Unknown bitcount, assume there is truncation.
return 1024U;
}
} else if (const auto *Uop = dyn_cast<UnaryOperator>(E)) {
// There is truncation when ~ is used.
if (Uop->getOpcode() == UO_Not)
return 1024U;
QualType T = Uop->getType();
return T->isIntegerType() ? Context.getIntWidth(T) : 1024U;
} else if (const auto *I = dyn_cast<IntegerLiteral>(E)) {
return I->getValue().getActiveBits();
}
return Context.getIntWidth(E->getType());
}
static int relativeIntSizes(BuiltinType::Kind Kind) {
switch (Kind) {
case BuiltinType::UChar:
return 1;
case BuiltinType::SChar:
return 1;
case BuiltinType::Char_U:
return 1;
case BuiltinType::Char_S:
return 1;
case BuiltinType::UShort:
return 2;
case BuiltinType::Short:
return 2;
case BuiltinType::UInt:
return 3;
case BuiltinType::Int:
return 3;
case BuiltinType::ULong:
return 4;
case BuiltinType::Long:
return 4;
case BuiltinType::ULongLong:
return 5;
case BuiltinType::LongLong:
return 5;
case BuiltinType::UInt128:
return 6;
case BuiltinType::Int128:
return 6;
default:
return 0;
}
}
static int relativeCharSizes(BuiltinType::Kind Kind) {
switch (Kind) {
case BuiltinType::UChar:
return 1;
case BuiltinType::SChar:
return 1;
case BuiltinType::Char_U:
return 1;
case BuiltinType::Char_S:
return 1;
case BuiltinType::Char16:
return 2;
case BuiltinType::Char32:
return 3;
default:
return 0;
}
}
static int relativeCharSizesW(BuiltinType::Kind Kind) {
switch (Kind) {
case BuiltinType::UChar:
return 1;
case BuiltinType::SChar:
return 1;
case BuiltinType::Char_U:
return 1;
case BuiltinType::Char_S:
return 1;
case BuiltinType::WChar_U:
return 2;
case BuiltinType::WChar_S:
return 2;
default:
return 0;
}
}
static bool isFirstWider(BuiltinType::Kind First, BuiltinType::Kind Second) {
int FirstSize, SecondSize;
if ((FirstSize = relativeIntSizes(First)) != 0 &&
(SecondSize = relativeIntSizes(Second)) != 0)
return FirstSize > SecondSize;
if ((FirstSize = relativeCharSizes(First)) != 0 &&
(SecondSize = relativeCharSizes(Second)) != 0)
return FirstSize > SecondSize;
if ((FirstSize = relativeCharSizesW(First)) != 0 &&
(SecondSize = relativeCharSizesW(Second)) != 0)
return FirstSize > SecondSize;
return false;
}
void MisplacedWideningCastCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Cast = Result.Nodes.getNodeAs<CastExpr>("Cast");
if (!CheckImplicitCasts && isa<ImplicitCastExpr>(Cast))
return;
if (Cast->getBeginLoc().isMacroID())
return;
const auto *Calc = Result.Nodes.getNodeAs<Expr>("Calc");
if (Calc->getBeginLoc().isMacroID())
return;
if (Cast->isTypeDependent() || Cast->isValueDependent() ||
Calc->isTypeDependent() || Calc->isValueDependent())
return;
ASTContext &Context = *Result.Context;
QualType CastType = Cast->getType();
QualType CalcType = Calc->getType();
// Explicit truncation using cast.
if (Context.getIntWidth(CastType) < Context.getIntWidth(CalcType))
return;
// If CalcType and CastType have same size then there is no real danger, but
// there can be a portability problem.
if (Context.getIntWidth(CastType) == Context.getIntWidth(CalcType)) {
const auto *CastBuiltinType =
dyn_cast<BuiltinType>(CastType->getUnqualifiedDesugaredType());
const auto *CalcBuiltinType =
dyn_cast<BuiltinType>(CalcType->getUnqualifiedDesugaredType());
if (!CastBuiltinType || !CalcBuiltinType)
return;
if (!isFirstWider(CastBuiltinType->getKind(), CalcBuiltinType->getKind()))
return;
}
// Don't write a warning if we can easily see that the result is not
// truncated.
if (Context.getIntWidth(CalcType) >= getMaxCalculationWidth(Context, Calc))
return;
diag(Cast->getBeginLoc(), "either cast from %0 to %1 is ineffective, or "
"there is loss of precision before the conversion")
<< CalcType << CastType;
}
} // namespace bugprone
} // namespace tidy
} // namespace clang
|
