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
|
//===- AnnotateFunctions.cpp ----------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Attribute plugin to mark a virtual method as ``call_super``, subclasses must
// call it in the overridden method.
//
// This example shows that attribute plugins combined with ``PluginASTAction``
// in Clang can do some of the same things which Java Annotations do.
//
// Unlike the other attribute plugin examples, this one does not attach an
// attribute AST node to the declaration AST node. Instead, it keeps a separate
// list of attributed declarations, which may be faster than using
// ``Decl::getAttr<T>()`` in some cases. The disadvantage of this approach is
// that the attribute is not part of the AST, which means that dumping the AST
// will lose the attribute information, pretty printing the AST won't write the
// attribute back out to source, and AST matchers will not be able to match
// against the attribute on the declaration.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Frontend/FrontendPluginRegistry.h"
#include "clang/Sema/ParsedAttr.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/ADT/SmallPtrSet.h"
using namespace clang;
namespace {
// Cached methods which are marked as 'call_super'.
llvm::SmallPtrSet<const CXXMethodDecl *, 16> MarkedMethods;
bool isMarkedAsCallSuper(const CXXMethodDecl *D) {
// Uses this way to avoid add an annotation attr to the AST.
return MarkedMethods.contains(D);
}
class MethodUsageVisitor : public RecursiveASTVisitor<MethodUsageVisitor> {
public:
bool IsOverriddenUsed = false;
explicit MethodUsageVisitor(
llvm::SmallPtrSet<const CXXMethodDecl *, 16> &MustCalledMethods)
: MustCalledMethods(MustCalledMethods) {}
bool VisitCallExpr(CallExpr *CallExpr) {
const CXXMethodDecl *Callee = nullptr;
for (const auto &MustCalled : MustCalledMethods) {
if (CallExpr->getCalleeDecl() == MustCalled) {
// Super is called.
// Notice that we cannot do delete or insert in the iteration
// when using SmallPtrSet.
Callee = MustCalled;
}
}
if (Callee)
MustCalledMethods.erase(Callee);
return true;
}
private:
llvm::SmallPtrSet<const CXXMethodDecl *, 16> &MustCalledMethods;
};
class CallSuperVisitor : public RecursiveASTVisitor<CallSuperVisitor> {
public:
CallSuperVisitor(DiagnosticsEngine &Diags) : Diags(Diags) {
WarningSuperNotCalled = Diags.getCustomDiagID(
DiagnosticsEngine::Warning,
"virtual function %q0 is marked as 'call_super' but this overriding "
"method does not call the base version");
NotePreviousCallSuperDeclaration = Diags.getCustomDiagID(
DiagnosticsEngine::Note, "function marked 'call_super' here");
}
bool VisitCXXMethodDecl(CXXMethodDecl *MethodDecl) {
if (MethodDecl->isThisDeclarationADefinition() && MethodDecl->hasBody()) {
// First find out which overridden methods are marked as 'call_super'
llvm::SmallPtrSet<const CXXMethodDecl *, 16> OverriddenMarkedMethods;
for (const auto *Overridden : MethodDecl->overridden_methods()) {
if (isMarkedAsCallSuper(Overridden)) {
OverriddenMarkedMethods.insert(Overridden);
}
}
// Now find if the superclass method is called in `MethodDecl`.
MethodUsageVisitor Visitor(OverriddenMarkedMethods);
Visitor.TraverseDecl(MethodDecl);
// After traversing, all methods left in `OverriddenMarkedMethods`
// are not called, warn about these.
for (const auto &LeftOverriddens : OverriddenMarkedMethods) {
Diags.Report(MethodDecl->getLocation(), WarningSuperNotCalled)
<< LeftOverriddens << MethodDecl;
Diags.Report(LeftOverriddens->getLocation(),
NotePreviousCallSuperDeclaration);
}
}
return true;
}
private:
DiagnosticsEngine &Diags;
unsigned WarningSuperNotCalled;
unsigned NotePreviousCallSuperDeclaration;
};
class CallSuperConsumer : public ASTConsumer {
public:
void HandleTranslationUnit(ASTContext &Context) override {
auto &Diags = Context.getDiagnostics();
for (const auto *Method : MarkedMethods) {
lateDiagAppertainsToDecl(Diags, Method);
}
CallSuperVisitor Visitor(Context.getDiagnostics());
Visitor.TraverseDecl(Context.getTranslationUnitDecl());
}
private:
// This function does checks which cannot be done in `diagAppertainsToDecl()`,
// typical example is checking Attributes (such as `FinalAttr`), on the time
// when `diagAppertainsToDecl()` is called, `FinalAttr` is not added into
// the AST yet.
void lateDiagAppertainsToDecl(DiagnosticsEngine &Diags,
const CXXMethodDecl *MethodDecl) {
if (MethodDecl->hasAttr<FinalAttr>()) {
unsigned ID = Diags.getCustomDiagID(
DiagnosticsEngine::Warning,
"'call_super' attribute marked on a final method");
Diags.Report(MethodDecl->getLocation(), ID);
}
}
};
class CallSuperAction : public PluginASTAction {
public:
std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
llvm::StringRef) override {
return std::make_unique<CallSuperConsumer>();
}
bool ParseArgs(const CompilerInstance &CI,
const std::vector<std::string> &args) override {
if (!args.empty() && args[0] == "help")
llvm::errs() << "Help for the CallSuperAttr plugin goes here\n";
return true;
}
PluginASTAction::ActionType getActionType() override {
return AddBeforeMainAction;
}
};
struct CallSuperAttrInfo : public ParsedAttrInfo {
CallSuperAttrInfo() {
OptArgs = 0;
static constexpr Spelling S[] = {
{ParsedAttr::AS_GNU, "call_super"},
{ParsedAttr::AS_CXX11, "clang::call_super"}};
Spellings = S;
}
bool diagAppertainsToDecl(Sema &S, const ParsedAttr &Attr,
const Decl *D) const override {
const auto *TheMethod = dyn_cast_or_null<CXXMethodDecl>(D);
if (!TheMethod || !TheMethod->isVirtual()) {
S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
<< Attr << Attr.isRegularKeywordAttribute()
<< ExpectedVirtualFunction;
return false;
}
MarkedMethods.insert(TheMethod);
return true;
}
AttrHandling handleDeclAttribute(Sema &S, Decl *D,
const ParsedAttr &Attr) const override {
// No need to add an attr object (usually an `AnnotateAttr` is added).
// Save the address of the Decl in a set, it maybe faster than compare to
// strings.
return AttributeNotApplied;
}
};
} // namespace
static FrontendPluginRegistry::Add<CallSuperAction>
X("call_super_plugin", "clang plugin, checks every overridden virtual "
"function whether called this function or not.");
static ParsedAttrInfoRegistry::Add<CallSuperAttrInfo>
Y("call_super_attr", "Attr plugin to define 'call_super' attribute");
|
