1 //===--- ProTypeVarargCheck.cpp - clang-tidy-------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "ProTypeVarargCheck.h"
10 #include "../utils/Matchers.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/ASTMatchers/ASTMatchers.h"
14 #include "clang/Basic/TargetInfo.h"
15 #include "clang/Lex/PPCallbacks.h"
16 #include "clang/Lex/Preprocessor.h"
17 #include "clang/Lex/Token.h"
18
19 using namespace clang::ast_matchers;
20
21 namespace clang::tidy::cppcoreguidelines {
22
23 const internal::VariadicDynCastAllOfMatcher<Stmt, VAArgExpr> VAArgExpr;
24
25 static constexpr StringRef AllowedVariadics[] = {
26 // clang-format off
27 "__builtin_isgreater",
28 "__builtin_isgreaterequal",
29 "__builtin_isless",
30 "__builtin_islessequal",
31 "__builtin_islessgreater",
32 "__builtin_isunordered",
33 "__builtin_fpclassify",
34 "__builtin_isfinite",
35 "__builtin_isinf",
36 "__builtin_isinf_sign",
37 "__builtin_isnan",
38 "__builtin_isnormal",
39 "__builtin_signbit",
40 "__builtin_constant_p",
41 "__builtin_classify_type",
42 "__builtin_va_start",
43 "__builtin_assume_aligned", // Documented as variadic to support default
44 // parameters.
45 "__builtin_prefetch", // Documented as variadic to support default
46 // parameters.
47 "__builtin_shufflevector", // Documented as variadic but with a defined
48 // number of args based on vector size.
49 "__builtin_convertvector",
50 "__builtin_call_with_static_chain",
51 "__builtin_annotation",
52 "__builtin_add_overflow",
53 "__builtin_sub_overflow",
54 "__builtin_mul_overflow",
55 "__builtin_preserve_access_index",
56 "__builtin_nontemporal_store",
57 "__builtin_nontemporal_load",
58 "__builtin_ms_va_start",
59 // clang-format on
60 };
61
62 static constexpr StringRef VaArgWarningMessage =
63 "do not use va_arg to define c-style vararg functions; "
64 "use variadic templates instead";
65
66 namespace {
AST_MATCHER(QualType,isVAList)67 AST_MATCHER(QualType, isVAList) {
68 ASTContext &Context = Finder->getASTContext();
69 QualType Desugar = Node.getDesugaredType(Context);
70 QualType NodeTy = Node.getUnqualifiedType();
71
72 auto CheckVaList = [](QualType NodeTy, QualType Expected,
73 const ASTContext &Context) {
74 if (NodeTy == Expected)
75 return true;
76 QualType Desugar = NodeTy;
77 QualType Ty;
78 do {
79 Ty = Desugar;
80 Desugar = Ty.getSingleStepDesugaredType(Context);
81 if (Desugar == Expected)
82 return true;
83 } while (Desugar != Ty);
84 return false;
85 };
86
87 // The internal implementation of __builtin_va_list depends on the target
88 // type. Some targets implements va_list as 'char *' or 'void *'.
89 // In these cases we need to remove all typedefs one by one to check this.
90 using BuiltinVaListKind = TargetInfo::BuiltinVaListKind;
91 BuiltinVaListKind VaListKind = Context.getTargetInfo().getBuiltinVaListKind();
92 if (VaListKind == BuiltinVaListKind::CharPtrBuiltinVaList ||
93 VaListKind == BuiltinVaListKind::VoidPtrBuiltinVaList) {
94 if (CheckVaList(NodeTy, Context.getBuiltinVaListType(), Context))
95 return true;
96 } else if (Desugar ==
97 Context.getBuiltinVaListType().getDesugaredType(Context)) {
98 return true;
99 }
100
101 // We also need to check the implementation of __builtin_ms_va_list in the
102 // same way, because it may differ from the va_list implementation.
103 if (Desugar == Context.getBuiltinMSVaListType().getDesugaredType(Context) &&
104 CheckVaList(NodeTy, Context.getBuiltinMSVaListType(), Context)) {
105 return true;
106 }
107
108 return false;
109 }
110
AST_MATCHER_P(AdjustedType,hasOriginalType,ast_matchers::internal::Matcher<QualType>,InnerType)111 AST_MATCHER_P(AdjustedType, hasOriginalType,
112 ast_matchers::internal::Matcher<QualType>, InnerType) {
113 return InnerType.matches(Node.getOriginalType(), Finder, Builder);
114 }
115
116 class VaArgPPCallbacks : public PPCallbacks {
117 public:
VaArgPPCallbacks(ProTypeVarargCheck * Check)118 VaArgPPCallbacks(ProTypeVarargCheck *Check) : Check(Check) {}
119
MacroExpands(const Token & MacroNameTok,const MacroDefinition & MD,SourceRange Range,const MacroArgs * Args)120 void MacroExpands(const Token &MacroNameTok, const MacroDefinition &MD,
121 SourceRange Range, const MacroArgs *Args) override {
122 if (MacroNameTok.getIdentifierInfo()->getName() == "va_arg") {
123 Check->diag(MacroNameTok.getLocation(), VaArgWarningMessage);
124 }
125 }
126
127 private:
128 ProTypeVarargCheck *Check;
129 };
130 } // namespace
131
registerMatchers(MatchFinder * Finder)132 void ProTypeVarargCheck::registerMatchers(MatchFinder *Finder) {
133 Finder->addMatcher(VAArgExpr().bind("va_use"), this);
134
135 Finder->addMatcher(
136 callExpr(callee(functionDecl(isVariadic(),
137 unless(hasAnyName(AllowedVariadics)))),
138 unless(hasAncestor(expr(matchers::hasUnevaluatedContext()))),
139 unless(hasAncestor(typeLoc())))
140 .bind("callvararg"),
141 this);
142
143 Finder->addMatcher(
144 varDecl(unless(parmVarDecl()),
145 hasType(qualType(
146 anyOf(isVAList(), decayedType(hasOriginalType(isVAList()))))))
147 .bind("va_list"),
148 this);
149 }
150
registerPPCallbacks(const SourceManager & SM,Preprocessor * PP,Preprocessor * ModuleExpanderPP)151 void ProTypeVarargCheck::registerPPCallbacks(const SourceManager &SM,
152 Preprocessor *PP,
153 Preprocessor *ModuleExpanderPP) {
154 PP->addPPCallbacks(std::make_unique<VaArgPPCallbacks>(this));
155 }
156
hasSingleVariadicArgumentWithValue(const CallExpr * C,uint64_t I)157 static bool hasSingleVariadicArgumentWithValue(const CallExpr *C, uint64_t I) {
158 const auto *FDecl = dyn_cast<FunctionDecl>(C->getCalleeDecl());
159 if (!FDecl)
160 return false;
161
162 auto N = FDecl->getNumParams(); // Number of parameters without '...'
163 if (C->getNumArgs() != N + 1)
164 return false; // more/less than one argument passed to '...'
165
166 const auto *IntLit =
167 dyn_cast<IntegerLiteral>(C->getArg(N)->IgnoreParenImpCasts());
168 if (!IntLit)
169 return false;
170
171 if (IntLit->getValue() != I)
172 return false;
173
174 return true;
175 }
176
check(const MatchFinder::MatchResult & Result)177 void ProTypeVarargCheck::check(const MatchFinder::MatchResult &Result) {
178 if (const auto *Matched = Result.Nodes.getNodeAs<CallExpr>("callvararg")) {
179 if (hasSingleVariadicArgumentWithValue(Matched, 0))
180 return;
181 diag(Matched->getExprLoc(), "do not call c-style vararg functions");
182 }
183
184 if (const auto *Matched = Result.Nodes.getNodeAs<Expr>("va_use")) {
185 diag(Matched->getExprLoc(), VaArgWarningMessage);
186 }
187
188 if (const auto *Matched = Result.Nodes.getNodeAs<VarDecl>("va_list")) {
189 auto SR = Matched->getSourceRange();
190 if (SR.isInvalid())
191 return; // some implicitly generated builtins take va_list
192 diag(SR.getBegin(), "do not declare variables of type va_list; "
193 "use variadic templates instead");
194 }
195 }
196
197 } // namespace clang::tidy::cppcoreguidelines
198