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
|
//===--- ForRangeCopyCheck.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 "ForRangeCopyCheck.h"
#include "../utils/DeclRefExprUtils.h"
#include "../utils/FixItHintUtils.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "../utils/TypeTraits.h"
#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
#include "clang/Basic/Diagnostic.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace performance {
ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnAllAutoCopies(Options.get("WarnOnAllAutoCopies", false)),
AllowedTypes(
utils::options::parseStringList(Options.get("AllowedTypes", ""))) {}
void ForRangeCopyCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnAllAutoCopies", WarnOnAllAutoCopies);
Options.store(Opts, "AllowedTypes",
utils::options::serializeStringList(AllowedTypes));
}
void ForRangeCopyCheck::registerMatchers(MatchFinder *Finder) {
// Match loop variables that are not references or pointers or are already
// initialized through MaterializeTemporaryExpr which indicates a type
// conversion.
auto HasReferenceOrPointerTypeOrIsAllowed = hasType(qualType(
unless(anyOf(hasCanonicalType(anyOf(referenceType(), pointerType())),
hasDeclaration(namedDecl(
matchers::matchesAnyListedName(AllowedTypes)))))));
auto IteratorReturnsValueType = cxxOperatorCallExpr(
hasOverloadedOperatorName("*"),
callee(
cxxMethodDecl(returns(unless(hasCanonicalType(referenceType()))))));
auto NotConstructedByCopy = cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(unless(isCopyConstructor()))));
auto ConstructedByConversion = cxxMemberCallExpr(callee(cxxConversionDecl()));
auto LoopVar =
varDecl(HasReferenceOrPointerTypeOrIsAllowed,
unless(hasInitializer(expr(hasDescendant(expr(
anyOf(materializeTemporaryExpr(), IteratorReturnsValueType,
NotConstructedByCopy, ConstructedByConversion)))))));
Finder->addMatcher(
traverse(TK_AsIs,
cxxForRangeStmt(hasLoopVariable(LoopVar.bind("loopVar")))
.bind("forRange")),
this);
}
void ForRangeCopyCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Var = Result.Nodes.getNodeAs<VarDecl>("loopVar");
// Ignore code in macros since we can't place the fixes correctly.
if (Var->getBeginLoc().isMacroID())
return;
if (handleConstValueCopy(*Var, *Result.Context))
return;
const auto *ForRange = Result.Nodes.getNodeAs<CXXForRangeStmt>("forRange");
handleCopyIsOnlyConstReferenced(*Var, *ForRange, *Result.Context);
}
bool ForRangeCopyCheck::handleConstValueCopy(const VarDecl &LoopVar,
ASTContext &Context) {
if (WarnOnAllAutoCopies) {
// For aggressive check just test that loop variable has auto type.
if (!isa<AutoType>(LoopVar.getType()))
return false;
} else if (!LoopVar.getType().isConstQualified()) {
return false;
}
llvm::Optional<bool> Expensive =
utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
if (!Expensive || !*Expensive)
return false;
auto Diagnostic =
diag(LoopVar.getLocation(),
"the loop variable's type is not a reference type; this creates a "
"copy in each iteration; consider making this a reference")
<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
if (!LoopVar.getType().isConstQualified()) {
if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
LoopVar, Context, DeclSpec::TQ::TQ_const))
Diagnostic << *Fix;
}
return true;
}
bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
const VarDecl &LoopVar, const CXXForRangeStmt &ForRange,
ASTContext &Context) {
llvm::Optional<bool> Expensive =
utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
if (LoopVar.getType().isConstQualified() || !Expensive || !*Expensive)
return false;
// We omit the case where the loop variable is not used in the loop body. E.g.
//
// for (auto _ : benchmark_state) {
// }
//
// Because the fix (changing to `const auto &`) will introduce an unused
// compiler warning which can't be suppressed.
// Since this case is very rare, it is safe to ignore it.
if (!ExprMutationAnalyzer(*ForRange.getBody(), Context).isMutated(&LoopVar) &&
!utils::decl_ref_expr::allDeclRefExprs(LoopVar, *ForRange.getBody(),
Context)
.empty()) {
auto Diag = diag(
LoopVar.getLocation(),
"loop variable is copied but only used as const reference; consider "
"making it a const reference");
if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
LoopVar, Context, DeclSpec::TQ::TQ_const))
Diag << *Fix << utils::fixit::changeVarDeclToReference(LoopVar, Context);
return true;
}
return false;
}
} // namespace performance
} // namespace tidy
} // namespace clang
|
