lib/Sema/SemaInit.cpp

//===--- SemaInit.cpp - Semantic Analysis for Initializers ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements semantic analysis for initializers.
//
//===----------------------------------------------------------------------===//

#include "Sema.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/Diagnostic.h"
#include <algorithm> // for std::count_if
#include <functional> // for std::mem_fun

namespace clang {

InitListChecker::InitListChecker(Sema *S, InitListExpr *IL, QualType &T) {
  hadError = false;
  SemaRef = S;

  unsigned newIndex = 0;

  CheckExplicitInitList(IL, T, newIndex);
}

int InitListChecker::numArrayElements(QualType DeclType) {
  // FIXME: use a proper constant
  int maxElements = 0x7FFFFFFF;
  if (const ConstantArrayType *CAT =
        SemaRef->Context.getAsConstantArrayType(DeclType)) {
    maxElements = static_cast<int>(CAT->getSize().getZExtValue());
  }
  return maxElements;
}

int InitListChecker::numStructUnionElements(QualType DeclType) {
  RecordDecl *structDecl = DeclType->getAsRecordType()->getDecl();
  const int InitializableMembers 
    = std::count_if(structDecl->field_begin(), structDecl->field_end(),
                    std::mem_fun(&FieldDecl::getDeclName));
  if (structDecl->isUnion())
    return std::min(InitializableMembers, 1);
  return InitializableMembers - structDecl->hasFlexibleArrayMember();
}

void InitListChecker::CheckImplicitInitList(InitListExpr *ParentIList, 
                                            QualType T, unsigned &Index) {
  llvm::SmallVector<Expr*, 4> InitExprs;
  int maxElements = 0;
  
  if (T->isArrayType())
    maxElements = numArrayElements(T);
  else if (T->isStructureType() || T->isUnionType())
    maxElements = numStructUnionElements(T);
  else if (T->isVectorType())
    maxElements = T->getAsVectorType()->getNumElements();
  else
    assert(0 && "CheckImplicitInitList(): Illegal type");

  if (maxElements == 0) {
    SemaRef->Diag(ParentIList->getInit(Index)->getLocStart(),
                  diag::err_implicit_empty_initializer);
    hadError = true;
    return;
  }

  // Check the element types *before* we create the implicit init list;
  // otherwise, we might end up taking the wrong number of elements
  unsigned NewIndex = Index;
  CheckListElementTypes(ParentIList, T, NewIndex);

  for (int i = 0; i < maxElements; ++i) {
    // Don't attempt to go past the end of the init list
    if (Index >= ParentIList->getNumInits())
      break;
    Expr* expr = ParentIList->getInit(Index);
    
    // Add the expr to the new implicit init list and remove if from the old.
    InitExprs.push_back(expr);
    ParentIList->removeInit(Index);
  }
  // Synthesize an "implicit" InitListExpr (marked by the invalid source locs).
  InitListExpr *ILE = new InitListExpr(SourceLocation(), 
                                       &InitExprs[0], InitExprs.size(), 
                                       SourceLocation(),
                                       ParentIList->hadDesignators());
  ILE->setImplicit();
  ILE->setType(T);

  // Modify the parent InitListExpr to point to the implicit InitListExpr.
  ParentIList->addInit(Index, ILE);
}

void InitListChecker::CheckExplicitInitList(InitListExpr *IList, QualType &T,
                                            unsigned &Index) {
  assert(IList->isExplicit() && "Illegal Implicit InitListExpr");

  CheckListElementTypes(IList, T, Index);
  IList->setType(T);
  if (hadError)
    return;

  if (Index < IList->getNumInits()) {
    // We have leftover initializers
    if (IList->getNumInits() > 0 &&
        SemaRef->IsStringLiteralInit(IList->getInit(Index), T)) {
      // Special-case
      SemaRef->Diag(IList->getInit(Index)->getLocStart(),
                    diag::err_excess_initializers_in_char_array_initializer)
        << IList->getInit(Index)->getSourceRange();
      hadError = true; 
    } else if (!T->isIncompleteType()) {
      // Don't warn for incomplete types, since we'll get an error elsewhere
      SemaRef->Diag(IList->getInit(Index)->getLocStart(), 
                    diag::warn_excess_initializers)
        << IList->getInit(Index)->getSourceRange();
    }
  }

  if (T->isScalarType())
    SemaRef->Diag(IList->getLocStart(), diag::warn_braces_around_scalar_init)
      << IList->getSourceRange();
}

void InitListChecker::CheckListElementTypes(InitListExpr *IList,
                                            QualType &DeclType, 
                                            unsigned &Index) {
  if (DeclType->isScalarType()) {
    CheckScalarType(IList, DeclType, Index);
  } else if (DeclType->isVectorType()) {
    CheckVectorType(IList, DeclType, Index);
  } else if (DeclType->isAggregateType() || DeclType->isUnionType()) {
    if (DeclType->isStructureType() || DeclType->isUnionType())
      CheckStructUnionTypes(IList, DeclType, Index);
    else if (DeclType->isArrayType()) 
      CheckArrayType(IList, DeclType, Index);
    else
      assert(0 && "Aggregate that isn't a function or array?!");
  } else if (DeclType->isVoidType() || DeclType->isFunctionType()) {
    // This type is invalid, issue a diagnostic.
    Index++;
    SemaRef->Diag(IList->getLocStart(), diag::err_illegal_initializer_type)
      << DeclType;
    hadError = true;
  } else {
    // In C, all types are either scalars or aggregates, but
    // additional handling is needed here for C++ (and possibly others?). 
    assert(0 && "Unsupported initializer type");
  }
}

void InitListChecker::CheckSubElementType(InitListExpr *IList,
                                          QualType ElemType, 
                                          unsigned &Index) {
  Expr* expr = IList->getInit(Index);
  if (InitListExpr *SubInitList = dyn_cast<InitListExpr>(expr)) {
    unsigned newIndex = 0;
    CheckExplicitInitList(SubInitList, ElemType, newIndex);
    Index++;
  } else if (StringLiteral *lit =
             SemaRef->IsStringLiteralInit(expr, ElemType)) {
    SemaRef->CheckStringLiteralInit(lit, ElemType);
    Index++;
  } else if (ElemType->isScalarType()) {
    CheckScalarType(IList, ElemType, Index);
  } else if (expr->getType()->getAsRecordType() &&
             SemaRef->Context.typesAreCompatible(
               expr->getType().getUnqualifiedType(),
               ElemType.getUnqualifiedType())) {
    Index++;
    // FIXME: Add checking
  } else {
    CheckImplicitInitList(IList, ElemType, Index);
    Index++;
  }
}

void InitListChecker::CheckScalarType(InitListExpr *IList, QualType &DeclType, 
                                      unsigned &Index) {
  if (Index < IList->getNumInits()) {
    Expr* expr = IList->getInit(Index);
    if (isa<InitListExpr>(expr)) {
      SemaRef->Diag(IList->getLocStart(),
                    diag::err_many_braces_around_scalar_init)
        << IList->getSourceRange();
      hadError = true;
      ++Index;
      return;
    }
    Expr *savExpr = expr; // Might be promoted by CheckSingleInitializer.
    if (SemaRef->CheckSingleInitializer(expr, DeclType))
      hadError = true; // types weren't compatible.
    else if (savExpr != expr)
      // The type was promoted, update initializer list.
      IList->setInit(Index, expr);
    ++Index;
  } else {
    SemaRef->Diag(IList->getLocStart(), diag::err_empty_scalar_initializer)
      << IList->getSourceRange();
    hadError = true;
    return;
  }
}

void InitListChecker::CheckVectorType(InitListExpr *IList, QualType DeclType, 
                                      unsigned &Index) {
  if (Index < IList->getNumInits()) {
    const VectorType *VT = DeclType->getAsVectorType();
    int maxElements = VT->getNumElements();
    QualType elementType = VT->getElementType();
    
    for (int i = 0; i < maxElements; ++i) {
      // Don't attempt to go past the end of the init list
      if (Index >= IList->getNumInits())
        break;
      CheckSubElementType(IList, elementType, Index);
    }
  }
}

void InitListChecker::CheckArrayType(InitListExpr *IList, QualType &DeclType, 
                                     unsigned &Index) {
  // Check for the special-case of initializing an array with a string.
  if (Index < IList->getNumInits()) {
    if (StringLiteral *lit = 
        SemaRef->IsStringLiteralInit(IList->getInit(Index), DeclType)) {
      SemaRef->CheckStringLiteralInit(lit, DeclType);
      ++Index;
      return;
    }
  }
  if (const VariableArrayType *VAT =
        SemaRef->Context.getAsVariableArrayType(DeclType)) {
    // Check for VLAs; in standard C it would be possible to check this
    // earlier, but I don't know where clang accepts VLAs (gcc accepts
    // them in all sorts of strange places).
    SemaRef->Diag(VAT->getSizeExpr()->getLocStart(),
                  diag::err_variable_object_no_init)
      << VAT->getSizeExpr()->getSourceRange();
    hadError = true;
    return;
  }

  int maxElements = numArrayElements(DeclType);
  QualType elementType = SemaRef->Context.getAsArrayType(DeclType)
                             ->getElementType();
  int numElements = 0;
  for (int i = 0; i < maxElements; ++i, ++numElements) {
    // Don't attempt to go past the end of the init list
    if (Index >= IList->getNumInits())
      break;
    CheckSubElementType(IList, elementType, Index);
  }
  if (DeclType->isIncompleteArrayType()) {
    // If this is an incomplete array type, the actual type needs to
    // be calculated here.
    if (numElements == 0) {
      // Sizing an array implicitly to zero is not allowed by ISO C,
      // but is supported by GNU.
      SemaRef->Diag(IList->getLocStart(),
                    diag::ext_typecheck_zero_array_size);
    }

    llvm::APSInt ConstVal(32);
    ConstVal = numElements;
    DeclType = SemaRef->Context.getConstantArrayType(elementType, ConstVal, 
                                                     ArrayType::Normal, 0);
  }
}

void InitListChecker::CheckStructUnionTypes(InitListExpr *IList, 
                                            QualType DeclType, 
                                            unsigned &Index) {
  RecordDecl* structDecl = DeclType->getAsRecordType()->getDecl();
    
  // If the record is invalid, some of it's members are invalid. To avoid
  // confusion, we forgo checking the intializer for the entire record.
  if (structDecl->isInvalidDecl()) {
    hadError = true;
    return;
  }    
  // If structDecl is a forward declaration, this loop won't do anything;
  // That's okay, because an error should get printed out elsewhere. It
  // might be worthwhile to skip over the rest of the initializer, though.
  RecordDecl *RD = DeclType->getAsRecordType()->getDecl();
  for (RecordDecl::field_iterator Field = RD->field_begin(),
                               FieldEnd = RD->field_end();
       Field != FieldEnd; ++Field) {
    // If we've hit the flexible array member at the end, we're done.
    if (Field->getType()->isIncompleteArrayType())
      break;

    // Don't attempt to go past the end of the init list
    if (Index >= IList->getNumInits())
      break;

    if (!Field->getIdentifier()) {
      // Don't initialize unnamed fields, e.g. "int : 20;"
      continue;
    }

    CheckSubElementType(IList, Field->getType(), Index);
    if (DeclType->isUnionType())
      break;
  }

  // FIXME: Implement flexible array initialization GCC extension (it's a 
  // really messy extension to implement, unfortunately...the necessary
  // information isn't actually even here!)
}
} // end namespace clang