lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp

   1 //===-- ASTResultSynthesizer.cpp ------------------------------------------===//
   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 "ASTResultSynthesizer.h"
  10
  11 #include "ClangASTImporter.h"
  12 #include "ClangPersistentVariables.h"
  13
  14 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
  15 #include "lldb/Target/Target.h"
  16 #include "lldb/Utility/LLDBAssert.h"
  17 #include "lldb/Utility/LLDBLog.h"
  18 #include "lldb/Utility/Log.h"
  19 #include "clang/AST/ASTContext.h"
  20 #include "clang/AST/Decl.h"
  21 #include "clang/AST/DeclCXX.h"
  22 #include "clang/AST/DeclGroup.h"
  23 #include "clang/AST/DeclObjC.h"
  24 #include "clang/AST/Expr.h"
  25 #include "clang/AST/Stmt.h"
  26 #include "clang/Parse/Parser.h"
  27 #include "clang/Sema/SemaDiagnostic.h"
  28 #include "llvm/Support/Casting.h"
  29 #include "llvm/Support/raw_ostream.h"
  30 #include <cstdlib>
  31
  32 using namespace llvm;
  33 using namespace clang;
  34 using namespace lldb_private;
  35
  36 ASTResultSynthesizer::ASTResultSynthesizer(ASTConsumer *passthrough,
  37                                            bool top_level, Target &target)
  38     : m_ast_context(nullptr), m_passthrough(passthrough),
  39       m_passthrough_sema(nullptr), m_target(target), m_sema(nullptr),
  40       m_top_level(top_level) {
  41   if (!m_passthrough)
  42     return;
  43
  44   m_passthrough_sema = dyn_cast<SemaConsumer>(passthrough);
  45 }
  46
  47 ASTResultSynthesizer::~ASTResultSynthesizer() = default;
  48
  49 void ASTResultSynthesizer::Initialize(ASTContext &Context) {
  50   m_ast_context = &Context;
  51
  52   if (m_passthrough)
  53     m_passthrough->Initialize(Context);
  54 }
  55
  56 void ASTResultSynthesizer::TransformTopLevelDecl(Decl *D) {
  57   Log *log = GetLog(LLDBLog::Expressions);
  58
  59   if (NamedDecl *named_decl = dyn_cast<NamedDecl>(D)) {
  60     if (log && log->GetVerbose()) {
  61       if (named_decl->getIdentifier())
  62         LLDB_LOGF(log, "TransformTopLevelDecl(%s)",
  63                   named_decl->getIdentifier()->getNameStart());
  64       else if (ObjCMethodDecl *method_decl = dyn_cast<ObjCMethodDecl>(D))
  65         LLDB_LOGF(log, "TransformTopLevelDecl(%s)",
  66                   method_decl->getSelector().getAsString().c_str());
  67       else
  68         LLDB_LOGF(log, "TransformTopLevelDecl(<complex>)");
  69     }
  70
  71     if (m_top_level) {
  72       RecordPersistentDecl(named_decl);
  73     }
  74   }
  75
  76   if (LinkageSpecDecl *linkage_spec_decl = dyn_cast<LinkageSpecDecl>(D)) {
  77     RecordDecl::decl_iterator decl_iterator;
  78
  79     for (decl_iterator = linkage_spec_decl->decls_begin();
  80          decl_iterator != linkage_spec_decl->decls_end(); ++decl_iterator) {
  81       TransformTopLevelDecl(*decl_iterator);
  82     }
  83   } else if (!m_top_level) {
  84     if (ObjCMethodDecl *method_decl = dyn_cast<ObjCMethodDecl>(D)) {
  85       if (m_ast_context &&
  86           !method_decl->getSelector().getAsString().compare("$__lldb_expr:")) {
  87         RecordPersistentTypes(method_decl);
  88         SynthesizeObjCMethodResult(method_decl);
  89       }
  90     } else if (FunctionDecl *function_decl = dyn_cast<FunctionDecl>(D)) {
  91       // When completing user input the body of the function may be a nullptr.
  92       if (m_ast_context && function_decl->hasBody() &&
  93           !function_decl->getNameInfo().getAsString().compare("$__lldb_expr")) {
  94         RecordPersistentTypes(function_decl);
  95         SynthesizeFunctionResult(function_decl);
  96       }
  97     }
  98   }
  99 }
 100
 101 bool ASTResultSynthesizer::HandleTopLevelDecl(DeclGroupRef D) {
 102   DeclGroupRef::iterator decl_iterator;
 103
 104   for (decl_iterator = D.begin(); decl_iterator != D.end(); ++decl_iterator) {
 105     Decl *decl = *decl_iterator;
 106
 107     TransformTopLevelDecl(decl);
 108   }
 109
 110   if (m_passthrough)
 111     return m_passthrough->HandleTopLevelDecl(D);
 112   return true;
 113 }
 114
 115 bool ASTResultSynthesizer::SynthesizeFunctionResult(FunctionDecl *FunDecl) {
 116   Log *log = GetLog(LLDBLog::Expressions);
 117
 118   if (!m_sema)
 119     return false;
 120
 121   FunctionDecl *function_decl = FunDecl;
 122
 123   if (!function_decl)
 124     return false;
 125
 126   if (log && log->GetVerbose()) {
 127     std::string s;
 128     raw_string_ostream os(s);
 129
 130     function_decl->print(os);
 131
 132     LLDB_LOGF(log, "Untransformed function AST:\n%s", s.c_str());
 133   }
 134
 135   Stmt *function_body = function_decl->getBody();
 136   CompoundStmt *compound_stmt = dyn_cast<CompoundStmt>(function_body);
 137
 138   bool ret = SynthesizeBodyResult(compound_stmt, function_decl);
 139
 140   if (log && log->GetVerbose()) {
 141     std::string s;
 142     raw_string_ostream os(s);
 143
 144     function_decl->print(os);
 145
 146     LLDB_LOGF(log, "Transformed function AST:\n%s", s.c_str());
 147   }
 148
 149   return ret;
 150 }
 151
 152 bool ASTResultSynthesizer::SynthesizeObjCMethodResult(
 153     ObjCMethodDecl *MethodDecl) {
 154   Log *log = GetLog(LLDBLog::Expressions);
 155
 156   if (!m_sema)
 157     return false;
 158
 159   if (!MethodDecl)
 160     return false;
 161
 162   if (log && log->GetVerbose()) {
 163     std::string s;
 164     raw_string_ostream os(s);
 165
 166     MethodDecl->print(os);
 167
 168     LLDB_LOGF(log, "Untransformed method AST:\n%s", s.c_str());
 169   }
 170
 171   Stmt *method_body = MethodDecl->getBody();
 172
 173   if (!method_body)
 174     return false;
 175
 176   CompoundStmt *compound_stmt = dyn_cast<CompoundStmt>(method_body);
 177
 178   bool ret = SynthesizeBodyResult(compound_stmt, MethodDecl);
 179
 180   if (log && log->GetVerbose()) {
 181     std::string s;
 182     raw_string_ostream os(s);
 183
 184     MethodDecl->print(os);
 185
 186     LLDB_LOGF(log, "Transformed method AST:\n%s", s.c_str());
 187   }
 188
 189   return ret;
 190 }
 191
 192 /// Returns true if LLDB can take the address of the given lvalue for the sake
 193 /// of capturing the expression result. Returns false if LLDB should instead
 194 /// store the expression result in a result variable.
 195 static bool CanTakeAddressOfLValue(const Expr *lvalue_expr) {
 196   assert(lvalue_expr->getValueKind() == VK_LValue &&
 197          "lvalue_expr not a lvalue");
 198
 199   QualType qt = lvalue_expr->getType();
 200   // If the lvalue has const-qualified non-volatile integral or enum type, then
 201   // the underlying value might come from a const static data member as
 202   // described in C++11 [class.static.data]p3. If that's the case, then the
 203   // value might not have an address if the user didn't also define the member
 204   // in a namespace scope. Taking the address would cause that LLDB later fails
 205   // to link the expression, so those lvalues should be stored in a result
 206   // variable.
 207   if (qt->isIntegralOrEnumerationType() && qt.isConstQualified() &&
 208       !qt.isVolatileQualified())
 209     return false;
 210   return true;
 211 }
 212
 213 bool ASTResultSynthesizer::SynthesizeBodyResult(CompoundStmt *Body,
 214                                                 DeclContext *DC) {
 215   Log *log = GetLog(LLDBLog::Expressions);
 216
 217   ASTContext &Ctx(*m_ast_context);
 218
 219   if (!Body)
 220     return false;
 221
 222   if (Body->body_empty())
 223     return false;
 224
 225   Stmt **last_stmt_ptr = Body->body_end() - 1;
 226   Stmt *last_stmt = *last_stmt_ptr;
 227
 228   while (isa<NullStmt>(last_stmt)) {
 229     if (last_stmt_ptr != Body->body_begin()) {
 230       last_stmt_ptr--;
 231       last_stmt = *last_stmt_ptr;
 232     } else {
 233       return false;
 234     }
 235   }
 236
 237   Expr *last_expr = dyn_cast<Expr>(last_stmt);
 238
 239   if (!last_expr)
 240     // No auxiliary variable necessary; expression returns void
 241     return true;
 242
 243   // In C++11, last_expr can be a LValueToRvalue implicit cast.  Strip that off
 244   // if that's the case.
 245
 246   do {
 247     ImplicitCastExpr *implicit_cast = dyn_cast<ImplicitCastExpr>(last_expr);
 248
 249     if (!implicit_cast)
 250       break;
 251
 252     if (implicit_cast->getCastKind() != CK_LValueToRValue)
 253       break;
 254
 255     last_expr = implicit_cast->getSubExpr();
 256   } while (false);
 257
 258   // is_lvalue is used to record whether the expression returns an assignable
 259   // Lvalue or an Rvalue.  This is relevant because they are handled
 260   // differently.
 261   //
 262   // For Lvalues
 263   //
 264   //   - In AST result synthesis (here!) the expression E is transformed into an
 265   //     initialization T *$__lldb_expr_result_ptr = &E.
 266   //
 267   //   - In structure allocation, a pointer-sized slot is allocated in the
 268   //     struct that is to be passed into the expression.
 269   //
 270   //   - In IR transformations, reads and writes to $__lldb_expr_result_ptr are
 271   //     redirected at an entry in the struct ($__lldb_arg) passed into the
 272   //     expression. (Other persistent variables are treated similarly, having
 273   //     been materialized as references, but in those cases the value of the
 274   //     reference itself is never modified.)
 275   //
 276   //   - During materialization, $0 (the result persistent variable) is ignored.
 277   //
 278   //   - During dematerialization, $0 is marked up as a load address with value
 279   //     equal to the contents of the structure entry.
 280   //
 281   //   - Note: if we cannot take an address of the resulting Lvalue (e.g. it's
 282   //     a static const member without an out-of-class definition), then we
 283   //     follow the Rvalue route.
 284   //
 285   // For Rvalues
 286   //
 287   //   - In AST result synthesis the expression E is transformed into an
 288   //     initialization static T $__lldb_expr_result = E.
 289   //
 290   //   - In structure allocation, a pointer-sized slot is allocated in the
 291   //     struct that is to be passed into the expression.
 292   //
 293   //   - In IR transformations, an instruction is inserted at the beginning of
 294   //     the function to dereference the pointer resident in the slot. Reads and
 295   //     writes to $__lldb_expr_result are redirected at that dereferenced
 296   //     version. Guard variables for the static variable are excised.
 297   //
 298   //   - During materialization, $0 (the result persistent variable) is
 299   //     populated with the location of a newly-allocated area of memory.
 300   //
 301   //   - During dematerialization, $0 is ignored.
 302
 303   bool is_lvalue = last_expr->getValueKind() == VK_LValue &&
 304                    last_expr->getObjectKind() == OK_Ordinary;
 305
 306   QualType expr_qual_type = last_expr->getType();
 307   const clang::Type *expr_type = expr_qual_type.getTypePtr();
 308
 309   if (!expr_type)
 310     return false;
 311
 312   if (expr_type->isVoidType())
 313     return true;
 314
 315   if (log) {
 316     std::string s = expr_qual_type.getAsString();
 317
 318     LLDB_LOGF(log, "Last statement is an %s with type: %s",
 319               (is_lvalue ? "lvalue" : "rvalue"), s.c_str());
 320   }
 321
 322   clang::VarDecl *result_decl = nullptr;
 323
 324   if (is_lvalue && CanTakeAddressOfLValue(last_expr)) {
 325     IdentifierInfo *result_ptr_id;
 326
 327     if (expr_type->isFunctionType())
 328       result_ptr_id =
 329           &Ctx.Idents.get("$__lldb_expr_result"); // functions actually should
 330                                                   // be treated like function
 331                                                   // pointers
 332     else
 333       result_ptr_id = &Ctx.Idents.get("$__lldb_expr_result_ptr");
 334
 335     m_sema->RequireCompleteType(last_expr->getSourceRange().getBegin(),
 336                                 expr_qual_type,
 337                                 clang::diag::err_incomplete_type);
 338
 339     QualType ptr_qual_type;
 340
 341     if (expr_qual_type->getAs<ObjCObjectType>() != nullptr)
 342       ptr_qual_type = Ctx.getObjCObjectPointerType(expr_qual_type);
 343     else
 344       ptr_qual_type = Ctx.getPointerType(expr_qual_type);
 345
 346     result_decl =
 347         VarDecl::Create(Ctx, DC, SourceLocation(), SourceLocation(),
 348                         result_ptr_id, ptr_qual_type, nullptr, SC_Static);
 349
 350     if (!result_decl)
 351       return false;
 352
 353     ExprResult address_of_expr =
 354         m_sema->CreateBuiltinUnaryOp(SourceLocation(), UO_AddrOf, last_expr);
 355     if (address_of_expr.get())
 356       m_sema->AddInitializerToDecl(result_decl, address_of_expr.get(), true);
 357     else
 358       return false;
 359   } else {
 360     IdentifierInfo &result_id = Ctx.Idents.get("$__lldb_expr_result");
 361
 362     result_decl =
 363         VarDecl::Create(Ctx, DC, SourceLocation(), SourceLocation(), &result_id,
 364                         expr_qual_type, nullptr, SC_Static);
 365
 366     if (!result_decl)
 367       return false;
 368
 369     m_sema->AddInitializerToDecl(result_decl, last_expr, true);
 370   }
 371
 372   DC->addDecl(result_decl);
 373
 374   ///////////////////////////////
 375   // call AddInitializerToDecl
 376   //
 377
 378   // m_sema->AddInitializerToDecl(result_decl, last_expr);
 379
 380   /////////////////////////////////
 381   // call ConvertDeclToDeclGroup
 382   //
 383
 384   Sema::DeclGroupPtrTy result_decl_group_ptr;
 385
 386   result_decl_group_ptr = m_sema->ConvertDeclToDeclGroup(result_decl);
 387
 388   ////////////////////////
 389   // call ActOnDeclStmt
 390   //
 391
 392   StmtResult result_initialization_stmt_result(m_sema->ActOnDeclStmt(
 393       result_decl_group_ptr, SourceLocation(), SourceLocation()));
 394
 395   ////////////////////////////////////////////////
 396   // replace the old statement with the new one
 397   //
 398
 399   *last_stmt_ptr = static_cast<Stmt *>(result_initialization_stmt_result.get());
 400
 401   return true;
 402 }
 403
 404 void ASTResultSynthesizer::HandleTranslationUnit(ASTContext &Ctx) {
 405   if (m_passthrough)
 406     m_passthrough->HandleTranslationUnit(Ctx);
 407 }
 408
 409 void ASTResultSynthesizer::RecordPersistentTypes(DeclContext *FunDeclCtx) {
 410   typedef DeclContext::specific_decl_iterator<TypeDecl> TypeDeclIterator;
 411
 412   for (TypeDeclIterator i = TypeDeclIterator(FunDeclCtx->decls_begin()),
 413                         e = TypeDeclIterator(FunDeclCtx->decls_end());
 414        i != e; ++i) {
 415     MaybeRecordPersistentType(*i);
 416   }
 417 }
 418
 419 void ASTResultSynthesizer::MaybeRecordPersistentType(TypeDecl *D) {
 420   if (!D->getIdentifier())
 421     return;
 422
 423   StringRef name = D->getName();
 424   if (name.empty() || name.front() != '$')
 425     return;
 426
 427   LLDB_LOG(GetLog(LLDBLog::Expressions), "Recording persistent type {0}", name);
 428
 429   m_decls.push_back(D);
 430 }
 431
 432 void ASTResultSynthesizer::RecordPersistentDecl(NamedDecl *D) {
 433   lldbassert(m_top_level);
 434
 435   if (!D->getIdentifier())
 436     return;
 437
 438   StringRef name = D->getName();
 439   if (name.empty())
 440     return;
 441
 442   LLDB_LOG(GetLog(LLDBLog::Expressions), "Recording persistent decl {0}", name);
 443
 444   m_decls.push_back(D);
 445 }
 446
 447 void ASTResultSynthesizer::CommitPersistentDecls() {
 448   auto *state =
 449       m_target.GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC);
 450   if (!state)
 451     return;
 452
 453   auto *persistent_vars = llvm::cast<ClangPersistentVariables>(state);
 454
 455   lldb::TypeSystemClangSP scratch_ts_sp = ScratchTypeSystemClang::GetForTarget(
 456       m_target, m_ast_context->getLangOpts());
 457
 458   for (clang::NamedDecl *decl : m_decls) {
 459     StringRef name = decl->getName();
 460
 461     Decl *D_scratch = persistent_vars->GetClangASTImporter()->DeportDecl(
 462         &scratch_ts_sp->getASTContext(), decl);
 463
 464     if (!D_scratch) {
 465       Log *log = GetLog(LLDBLog::Expressions);
 466
 467       if (log) {
 468         std::string s;
 469         llvm::raw_string_ostream ss(s);
 470         decl->dump(ss);
 471
 472         LLDB_LOGF(log, "Couldn't commit persistent  decl: %s\n", s.c_str());
 473       }
 474
 475       continue;
 476     }
 477
 478     if (NamedDecl *NamedDecl_scratch = dyn_cast<NamedDecl>(D_scratch))
 479       persistent_vars->RegisterPersistentDecl(ConstString(name),
 480                                               NamedDecl_scratch, scratch_ts_sp);
 481   }
 482 }
 483
 484 void ASTResultSynthesizer::HandleTagDeclDefinition(TagDecl *D) {
 485   if (m_passthrough)
 486     m_passthrough->HandleTagDeclDefinition(D);
 487 }
 488
 489 void ASTResultSynthesizer::CompleteTentativeDefinition(VarDecl *D) {
 490   if (m_passthrough)
 491     m_passthrough->CompleteTentativeDefinition(D);
 492 }
 493
 494 void ASTResultSynthesizer::HandleVTable(CXXRecordDecl *RD) {
 495   if (m_passthrough)
 496     m_passthrough->HandleVTable(RD);
 497 }
 498
 499 void ASTResultSynthesizer::PrintStats() {
 500   if (m_passthrough)
 501     m_passthrough->PrintStats();
 502 }
 503
 504 void ASTResultSynthesizer::InitializeSema(Sema &S) {
 505   m_sema = &S;
 506
 507   if (m_passthrough_sema)
 508     m_passthrough_sema->InitializeSema(S);
 509 }
 510
 511 void ASTResultSynthesizer::ForgetSema() {
 512   m_sema = nullptr;
 513
 514   if (m_passthrough_sema)
 515     m_passthrough_sema->ForgetSema();
 516 }