BodyFarm.cpp revision 280031 
1//== BodyFarm.cpp  - Factory for conjuring up fake bodies ----------*- C++ -*-//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// BodyFarm is a factory for creating faux implementations for functions/methods
11// for analysis purposes.
12//
13//===----------------------------------------------------------------------===//
14
15#include "BodyFarm.h"
16#include "clang/AST/ASTContext.h"
17#include "clang/AST/Decl.h"
18#include "clang/AST/Expr.h"
19#include "clang/AST/ExprObjC.h"
20#include "clang/Analysis/CodeInjector.h"
21#include "llvm/ADT/StringSwitch.h"
22
23using namespace clang;
24
25//===----------------------------------------------------------------------===//
26// Helper creation functions for constructing faux ASTs.
27//===----------------------------------------------------------------------===//
28
29static bool isDispatchBlock(QualType Ty) {
30  // Is it a block pointer?
31  const BlockPointerType *BPT = Ty->getAs<BlockPointerType>();
32  if (!BPT)
33    return false;
34
35  // Check if the block pointer type takes no arguments and
36  // returns void.
37  const FunctionProtoType *FT =
38  BPT->getPointeeType()->getAs<FunctionProtoType>();
39  if (!FT || !FT->getReturnType()->isVoidType() || FT->getNumParams() != 0)
40    return false;
41
42  return true;
43}
44
45namespace {
46class ASTMaker {
47public:
48  ASTMaker(ASTContext &C) : C(C) {}
49
50  /// Create a new BinaryOperator representing a simple assignment.
51  BinaryOperator *makeAssignment(const Expr *LHS, const Expr *RHS, QualType Ty);
52
53  /// Create a new BinaryOperator representing a comparison.
54  BinaryOperator *makeComparison(const Expr *LHS, const Expr *RHS,
55                                 BinaryOperator::Opcode Op);
56
57  /// Create a new compound stmt using the provided statements.
58  CompoundStmt *makeCompound(ArrayRef<Stmt*>);
59
60  /// Create a new DeclRefExpr for the referenced variable.
61  DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
62
63  /// Create a new UnaryOperator representing a dereference.
64  UnaryOperator *makeDereference(const Expr *Arg, QualType Ty);
65
66  /// Create an implicit cast for an integer conversion.
67  Expr *makeIntegralCast(const Expr *Arg, QualType Ty);
68
69  /// Create an implicit cast to a builtin boolean type.
70  ImplicitCastExpr *makeIntegralCastToBoolean(const Expr *Arg);
71
72  // Create an implicit cast for lvalue-to-rvaluate conversions.
73  ImplicitCastExpr *makeLvalueToRvalue(const Expr *Arg, QualType Ty);
74
75  /// Create an Objective-C bool literal.
76  ObjCBoolLiteralExpr *makeObjCBool(bool Val);
77
78  /// Create an Objective-C ivar reference.
79  ObjCIvarRefExpr *makeObjCIvarRef(const Expr *Base, const ObjCIvarDecl *IVar);
80
81  /// Create a Return statement.
82  ReturnStmt *makeReturn(const Expr *RetVal);
83
84private:
85  ASTContext &C;
86};
87}
88
89BinaryOperator *ASTMaker::makeAssignment(const Expr *LHS, const Expr *RHS,
90                                         QualType Ty) {
91 return new (C) BinaryOperator(const_cast<Expr*>(LHS), const_cast<Expr*>(RHS),
92                               BO_Assign, Ty, VK_RValue,
93                               OK_Ordinary, SourceLocation(), false);
94}
95
96BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
97                                         BinaryOperator::Opcode Op) {
98  assert(BinaryOperator::isLogicalOp(Op) ||
99         BinaryOperator::isComparisonOp(Op));
100  return new (C) BinaryOperator(const_cast<Expr*>(LHS),
101                                const_cast<Expr*>(RHS),
102                                Op,
103                                C.getLogicalOperationType(),
104                                VK_RValue,
105                                OK_Ordinary, SourceLocation(), false);
106}
107
108CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
109  return new (C) CompoundStmt(C, Stmts, SourceLocation(), SourceLocation());
110}
111
112DeclRefExpr *ASTMaker::makeDeclRefExpr(const VarDecl *D) {
113  DeclRefExpr *DR =
114    DeclRefExpr::Create(/* Ctx = */ C,
115                        /* QualifierLoc = */ NestedNameSpecifierLoc(),
116                        /* TemplateKWLoc = */ SourceLocation(),
117                        /* D = */ const_cast<VarDecl*>(D),
118                        /* RefersToEnclosingVariableOrCapture = */ false,
119                        /* NameLoc = */ SourceLocation(),
120                        /* T = */ D->getType(),
121                        /* VK = */ VK_LValue);
122  return DR;
123}
124
125UnaryOperator *ASTMaker::makeDereference(const Expr *Arg, QualType Ty) {
126  return new (C) UnaryOperator(const_cast<Expr*>(Arg), UO_Deref, Ty,
127                               VK_LValue, OK_Ordinary, SourceLocation());
128}
129
130ImplicitCastExpr *ASTMaker::makeLvalueToRvalue(const Expr *Arg, QualType Ty) {
131  return ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
132                                  const_cast<Expr*>(Arg), nullptr, VK_RValue);
133}
134
135Expr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
136  if (Arg->getType() == Ty)
137    return const_cast<Expr*>(Arg);
138
139  return ImplicitCastExpr::Create(C, Ty, CK_IntegralCast,
140                                  const_cast<Expr*>(Arg), nullptr, VK_RValue);
141}
142
143ImplicitCastExpr *ASTMaker::makeIntegralCastToBoolean(const Expr *Arg) {
144  return ImplicitCastExpr::Create(C, C.BoolTy, CK_IntegralToBoolean,
145                                  const_cast<Expr*>(Arg), nullptr, VK_RValue);
146}
147
148ObjCBoolLiteralExpr *ASTMaker::makeObjCBool(bool Val) {
149  QualType Ty = C.getBOOLDecl() ? C.getBOOLType() : C.ObjCBuiltinBoolTy;
150  return new (C) ObjCBoolLiteralExpr(Val, Ty, SourceLocation());
151}
152
153ObjCIvarRefExpr *ASTMaker::makeObjCIvarRef(const Expr *Base,
154                                           const ObjCIvarDecl *IVar) {
155  return new (C) ObjCIvarRefExpr(const_cast<ObjCIvarDecl*>(IVar),
156                                 IVar->getType(), SourceLocation(),
157                                 SourceLocation(), const_cast<Expr*>(Base),
158                                 /*arrow=*/true, /*free=*/false);
159}
160
161
162ReturnStmt *ASTMaker::makeReturn(const Expr *RetVal) {
163  return new (C) ReturnStmt(SourceLocation(), const_cast<Expr*>(RetVal),
164                            nullptr);
165}
166
167//===----------------------------------------------------------------------===//
168// Creation functions for faux ASTs.
169//===----------------------------------------------------------------------===//
170
171typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
172
173/// Create a fake body for dispatch_once.
174static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
175  // Check if we have at least two parameters.
176  if (D->param_size() != 2)
177    return nullptr;
178
179  // Check if the first parameter is a pointer to integer type.
180  const ParmVarDecl *Predicate = D->getParamDecl(0);
181  QualType PredicateQPtrTy = Predicate->getType();
182  const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
183  if (!PredicatePtrTy)
184    return nullptr;
185  QualType PredicateTy = PredicatePtrTy->getPointeeType();
186  if (!PredicateTy->isIntegerType())
187    return nullptr;
188
189  // Check if the second parameter is the proper block type.
190  const ParmVarDecl *Block = D->getParamDecl(1);
191  QualType Ty = Block->getType();
192  if (!isDispatchBlock(Ty))
193    return nullptr;
194
195  // Everything checks out.  Create a fakse body that checks the predicate,
196  // sets it, and calls the block.  Basically, an AST dump of:
197  //
198  // void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
199  //  if (!*predicate) {
200  //    *predicate = 1;
201  //    block();
202  //  }
203  // }
204
205  ASTMaker M(C);
206
207  // (1) Create the call.
208  DeclRefExpr *DR = M.makeDeclRefExpr(Block);
209  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
210  CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
211                                  SourceLocation());
212
213  // (2) Create the assignment to the predicate.
214  IntegerLiteral *IL =
215    IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
216                           C.IntTy, SourceLocation());
217  BinaryOperator *B =
218    M.makeAssignment(
219       M.makeDereference(
220          M.makeLvalueToRvalue(
221            M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
222            PredicateTy),
223       M.makeIntegralCast(IL, PredicateTy),
224       PredicateTy);
225
226  // (3) Create the compound statement.
227  Stmt *Stmts[] = { B, CE };
228  CompoundStmt *CS = M.makeCompound(Stmts);
229
230  // (4) Create the 'if' condition.
231  ImplicitCastExpr *LValToRval =
232    M.makeLvalueToRvalue(
233      M.makeDereference(
234        M.makeLvalueToRvalue(
235          M.makeDeclRefExpr(Predicate),
236          PredicateQPtrTy),
237        PredicateTy),
238    PredicateTy);
239
240  UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
241                                           VK_RValue, OK_Ordinary,
242                                           SourceLocation());
243
244  // (5) Create the 'if' statement.
245  IfStmt *If = new (C) IfStmt(C, SourceLocation(), nullptr, UO, CS);
246  return If;
247}
248
249/// Create a fake body for dispatch_sync.
250static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
251  // Check if we have at least two parameters.
252  if (D->param_size() != 2)
253    return nullptr;
254
255  // Check if the second parameter is a block.
256  const ParmVarDecl *PV = D->getParamDecl(1);
257  QualType Ty = PV->getType();
258  if (!isDispatchBlock(Ty))
259    return nullptr;
260
261  // Everything checks out.  Create a fake body that just calls the block.
262  // This is basically just an AST dump of:
263  //
264  // void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
265  //   block();
266  // }
267  //
268  ASTMaker M(C);
269  DeclRefExpr *DR = M.makeDeclRefExpr(PV);
270  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
271  CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
272                                  SourceLocation());
273  return CE;
274}
275
276static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
277{
278  // There are exactly 3 arguments.
279  if (D->param_size() != 3)
280    return nullptr;
281
282  // Signature:
283  // _Bool OSAtomicCompareAndSwapPtr(void *__oldValue,
284  //                                 void *__newValue,
285  //                                 void * volatile *__theValue)
286  // Generate body:
287  //   if (oldValue == *theValue) {
288  //    *theValue = newValue;
289  //    return YES;
290  //   }
291  //   else return NO;
292
293  QualType ResultTy = D->getReturnType();
294  bool isBoolean = ResultTy->isBooleanType();
295  if (!isBoolean && !ResultTy->isIntegralType(C))
296    return nullptr;
297
298  const ParmVarDecl *OldValue = D->getParamDecl(0);
299  QualType OldValueTy = OldValue->getType();
300
301  const ParmVarDecl *NewValue = D->getParamDecl(1);
302  QualType NewValueTy = NewValue->getType();
303
304  assert(OldValueTy == NewValueTy);
305
306  const ParmVarDecl *TheValue = D->getParamDecl(2);
307  QualType TheValueTy = TheValue->getType();
308  const PointerType *PT = TheValueTy->getAs<PointerType>();
309  if (!PT)
310    return nullptr;
311  QualType PointeeTy = PT->getPointeeType();
312
313  ASTMaker M(C);
314  // Construct the comparison.
315  Expr *Comparison =
316    M.makeComparison(
317      M.makeLvalueToRvalue(M.makeDeclRefExpr(OldValue), OldValueTy),
318      M.makeLvalueToRvalue(
319        M.makeDereference(
320          M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
321          PointeeTy),
322        PointeeTy),
323      BO_EQ);
324
325  // Construct the body of the IfStmt.
326  Stmt *Stmts[2];
327  Stmts[0] =
328    M.makeAssignment(
329      M.makeDereference(
330        M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
331        PointeeTy),
332      M.makeLvalueToRvalue(M.makeDeclRefExpr(NewValue), NewValueTy),
333      NewValueTy);
334
335  Expr *BoolVal = M.makeObjCBool(true);
336  Expr *RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
337                           : M.makeIntegralCast(BoolVal, ResultTy);
338  Stmts[1] = M.makeReturn(RetVal);
339  CompoundStmt *Body = M.makeCompound(Stmts);
340
341  // Construct the else clause.
342  BoolVal = M.makeObjCBool(false);
343  RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
344                     : M.makeIntegralCast(BoolVal, ResultTy);
345  Stmt *Else = M.makeReturn(RetVal);
346
347  /// Construct the If.
348  Stmt *If =
349    new (C) IfStmt(C, SourceLocation(), nullptr, Comparison, Body,
350                   SourceLocation(), Else);
351
352  return If;
353}
354
355Stmt *BodyFarm::getBody(const FunctionDecl *D) {
356  D = D->getCanonicalDecl();
357
358  Optional<Stmt *> &Val = Bodies[D];
359  if (Val.hasValue())
360    return Val.getValue();
361
362  Val = nullptr;
363
364  if (D->getIdentifier() == nullptr)
365    return nullptr;
366
367  StringRef Name = D->getName();
368  if (Name.empty())
369    return nullptr;
370
371  FunctionFarmer FF;
372
373  if (Name.startswith("OSAtomicCompareAndSwap") ||
374      Name.startswith("objc_atomicCompareAndSwap")) {
375    FF = create_OSAtomicCompareAndSwap;
376  }
377  else {
378    FF = llvm::StringSwitch<FunctionFarmer>(Name)
379          .Case("dispatch_sync", create_dispatch_sync)
380          .Case("dispatch_once", create_dispatch_once)
381          .Default(nullptr);
382  }
383
384  if (FF) { Val = FF(C, D); }
385  else if (Injector) { Val = Injector->getBody(D); }
386  return Val.getValue();
387}
388
389static Stmt *createObjCPropertyGetter(ASTContext &Ctx,
390                                      const ObjCPropertyDecl *Prop) {
391  // First, find the backing ivar.
392  const ObjCIvarDecl *IVar = Prop->getPropertyIvarDecl();
393  if (!IVar)
394    return nullptr;
395
396  // Ignore weak variables, which have special behavior.
397  if (Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak)
398    return nullptr;
399
400  // Look to see if Sema has synthesized a body for us. This happens in
401  // Objective-C++ because the return value may be a C++ class type with a
402  // non-trivial copy constructor. We can only do this if we can find the
403  // @synthesize for this property, though (or if we know it's been auto-
404  // synthesized).
405  const ObjCImplementationDecl *ImplDecl =
406    IVar->getContainingInterface()->getImplementation();
407  if (ImplDecl) {
408    for (const auto *I : ImplDecl->property_impls()) {
409      if (I->getPropertyDecl() != Prop)
410        continue;
411
412      if (I->getGetterCXXConstructor()) {
413        ASTMaker M(Ctx);
414        return M.makeReturn(I->getGetterCXXConstructor());
415      }
416    }
417  }
418
419  // Sanity check that the property is the same type as the ivar, or a
420  // reference to it, and that it is either an object pointer or trivially
421  // copyable.
422  if (!Ctx.hasSameUnqualifiedType(IVar->getType(),
423                                  Prop->getType().getNonReferenceType()))
424    return nullptr;
425  if (!IVar->getType()->isObjCLifetimeType() &&
426      !IVar->getType().isTriviallyCopyableType(Ctx))
427    return nullptr;
428
429  // Generate our body:
430  //   return self->_ivar;
431  ASTMaker M(Ctx);
432
433  const VarDecl *selfVar = Prop->getGetterMethodDecl()->getSelfDecl();
434
435  Expr *loadedIVar =
436    M.makeObjCIvarRef(
437      M.makeLvalueToRvalue(
438        M.makeDeclRefExpr(selfVar),
439        selfVar->getType()),
440      IVar);
441
442  if (!Prop->getType()->isReferenceType())
443    loadedIVar = M.makeLvalueToRvalue(loadedIVar, IVar->getType());
444
445  return M.makeReturn(loadedIVar);
446}
447
448Stmt *BodyFarm::getBody(const ObjCMethodDecl *D) {
449  // We currently only know how to synthesize property accessors.
450  if (!D->isPropertyAccessor())
451    return nullptr;
452
453  D = D->getCanonicalDecl();
454
455  Optional<Stmt *> &Val = Bodies[D];
456  if (Val.hasValue())
457    return Val.getValue();
458  Val = nullptr;
459
460  const ObjCPropertyDecl *Prop = D->findPropertyDecl();
461  if (!Prop)
462    return nullptr;
463
464  // For now, we only synthesize getters.
465  if (D->param_size() != 0)
466    return nullptr;
467
468  Val = createObjCPropertyGetter(C, Prop);
469
470  return Val.getValue();
471}
472
473