1//== CheckerContext.cpp - Context info for path-sensitive checkers-----------=//
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// This file defines CheckerContext that provides contextual info for
10// path-sensitive checkers.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
15#include "clang/Basic/Builtins.h"
16#include "clang/Lex/Lexer.h"
17#include "llvm/ADT/StringExtras.h"
18
19using namespace clang;
20using namespace ento;
21
22const FunctionDecl *CheckerContext::getCalleeDecl(const CallExpr *CE) const {
23 const FunctionDecl *D = CE->getDirectCallee();
24 if (D)
25 return D;
26
27 const Expr *Callee = CE->getCallee();
28 SVal L = Pred->getSVal(S: Callee);
29 return L.getAsFunctionDecl();
30}
31
32StringRef CheckerContext::getCalleeName(const FunctionDecl *FunDecl) const {
33 if (!FunDecl)
34 return StringRef();
35 IdentifierInfo *funI = FunDecl->getIdentifier();
36 if (!funI)
37 return StringRef();
38 return funI->getName();
39}
40
41StringRef CheckerContext::getDeclDescription(const Decl *D) {
42 if (isa<ObjCMethodDecl, CXXMethodDecl>(Val: D))
43 return "method";
44 if (isa<BlockDecl>(Val: D))
45 return "anonymous block";
46 return "function";
47}
48
49bool CheckerContext::isCLibraryFunction(const FunctionDecl *FD,
50 StringRef Name) {
51 // To avoid false positives (Ex: finding user defined functions with
52 // similar names), only perform fuzzy name matching when it's a builtin.
53 // Using a string compare is slow, we might want to switch on BuiltinID here.
54 unsigned BId = FD->getBuiltinID();
55 if (BId != 0) {
56 if (Name.empty())
57 return true;
58 std::string BName = FD->getASTContext().BuiltinInfo.getName(ID: BId);
59 size_t start = BName.find(svt: Name);
60 if (start != StringRef::npos) {
61 // Accept exact match.
62 if (BName.size() == Name.size())
63 return true;
64
65 // v-- match starts here
66 // ...xxxxx...
67 // _xxxxx_
68 // ^ ^ lookbehind and lookahead characters
69
70 const auto MatchPredecessor = [&]() -> bool {
71 return start <= 0 || !llvm::isAlpha(C: BName[start - 1]);
72 };
73 const auto MatchSuccessor = [&]() -> bool {
74 std::size_t LookbehindPlace = start + Name.size();
75 return LookbehindPlace >= BName.size() ||
76 !llvm::isAlpha(C: BName[LookbehindPlace]);
77 };
78
79 if (MatchPredecessor() && MatchSuccessor())
80 return true;
81 }
82 }
83
84 const IdentifierInfo *II = FD->getIdentifier();
85 // If this is a special C++ name without IdentifierInfo, it can't be a
86 // C library function.
87 if (!II)
88 return false;
89
90 // C library functions are either declared directly within a TU (the common
91 // case) or they are accessed through the namespace `std` (when they are used
92 // in C++ via headers like <cstdlib>).
93 const DeclContext *DC = FD->getDeclContext()->getRedeclContext();
94 if (!(DC->isTranslationUnit() || DC->isStdNamespace()))
95 return false;
96
97 // If this function is not externally visible, it is not a C library function.
98 // Note that we make an exception for inline functions, which may be
99 // declared in header files without external linkage.
100 if (!FD->isInlined() && !FD->isExternallyVisible())
101 return false;
102
103 if (Name.empty())
104 return true;
105
106 StringRef FName = II->getName();
107 if (FName == Name)
108 return true;
109
110 if (FName.starts_with(Prefix: "__inline") && FName.contains(Other: Name))
111 return true;
112
113 return false;
114}
115
116bool CheckerContext::isHardenedVariantOf(const FunctionDecl *FD,
117 StringRef Name) {
118 const IdentifierInfo *II = FD->getIdentifier();
119 if (!II)
120 return false;
121
122 auto CompletelyMatchesParts = [II](auto... Parts) -> bool {
123 StringRef FName = II->getName();
124 return (FName.consume_front(Prefix: Parts) && ...) && FName.empty();
125 };
126
127 return CompletelyMatchesParts("__", Name, "_chk") ||
128 CompletelyMatchesParts("__builtin_", "__", Name, "_chk");
129}
130
131StringRef CheckerContext::getMacroNameOrSpelling(SourceLocation &Loc) {
132 if (Loc.isMacroID())
133 return Lexer::getImmediateMacroName(Loc, SM: getSourceManager(),
134 LangOpts: getLangOpts());
135 SmallString<16> buf;
136 return Lexer::getSpelling(loc: Loc, buffer&: buf, SM: getSourceManager(), options: getLangOpts());
137}
138
139/// Evaluate comparison and return true if it's known that condition is true
140static bool evalComparison(SVal LHSVal, BinaryOperatorKind ComparisonOp,
141 SVal RHSVal, ProgramStateRef State) {
142 if (LHSVal.isUnknownOrUndef())
143 return false;
144 ProgramStateManager &Mgr = State->getStateManager();
145 if (!isa<NonLoc>(Val: LHSVal)) {
146 LHSVal = Mgr.getStoreManager().getBinding(store: State->getStore(),
147 loc: LHSVal.castAs<Loc>());
148 if (LHSVal.isUnknownOrUndef() || !isa<NonLoc>(Val: LHSVal))
149 return false;
150 }
151
152 SValBuilder &Bldr = Mgr.getSValBuilder();
153 SVal Eval = Bldr.evalBinOp(state: State, op: ComparisonOp, lhs: LHSVal, rhs: RHSVal,
154 type: Bldr.getConditionType());
155 if (Eval.isUnknownOrUndef())
156 return false;
157 ProgramStateRef StTrue, StFalse;
158 std::tie(args&: StTrue, args&: StFalse) = State->assume(Cond: Eval.castAs<DefinedSVal>());
159 return StTrue && !StFalse;
160}
161
162bool CheckerContext::isGreaterOrEqual(const Expr *E, unsigned long long Val) {
163 DefinedSVal V = getSValBuilder().makeIntVal(integer: Val, type: getASTContext().LongLongTy);
164 return evalComparison(LHSVal: getSVal(S: E), ComparisonOp: BO_GE, RHSVal: V, State: getState());
165}
166
167bool CheckerContext::isNegative(const Expr *E) {
168 DefinedSVal V = getSValBuilder().makeIntVal(integer: 0, isUnsigned: false);
169 return evalComparison(LHSVal: getSVal(S: E), ComparisonOp: BO_LT, RHSVal: V, State: getState());
170}
171