path: root/lib/Sema/SemaStmt.cpp

//===--- SemaStmt.cpp - Semantic Analysis for Statements ------------------===//
//
//                     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 statements.
//
//===----------------------------------------------------------------------===//

#include "Sema.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/Diagnostic.h"
using namespace clang;

Sema::OwningStmtResult Sema::ActOnExprStmt(ExprArg expr) {
  Expr *E = static_cast<Expr*>(expr.release());
  assert(E && "ActOnExprStmt(): missing expression");

  // C99 6.8.3p2: The expression in an expression statement is evaluated as a
  // void expression for its side effects.  Conversion to void allows any
  // operand, even incomplete types.

  // Same thing in for stmt first clause (when expr) and third clause.
  return Owned(static_cast<Stmt*>(E));
}


Sema::OwningStmtResult Sema::ActOnNullStmt(SourceLocation SemiLoc) {
  return Owned(new NullStmt(SemiLoc));
}

Sema::OwningStmtResult Sema::ActOnDeclStmt(DeclTy *decl,
                                           SourceLocation StartLoc,
                                           SourceLocation EndLoc) {
  if (decl == 0)
    return StmtError();

  ScopedDecl *SD = cast<ScopedDecl>(static_cast<Decl *>(decl));

  // This is a temporary hack until we are always passing around
  // DeclGroupRefs.
  llvm::SmallVector<Decl*, 10> decls;
  while (SD) { 
    ScopedDecl* d = SD;
    SD = SD->getNextDeclarator();
    d->setNextDeclarator(0);
    decls.push_back(d);
  }

  assert (!decls.empty());

  if (decls.size() == 1) {
    DeclGroupOwningRef DG(*decls.begin());                      
    return Owned(new DeclStmt(DG, StartLoc, EndLoc));
  }
  else {
    DeclGroupOwningRef DG(DeclGroup::Create(Context, decls.size(), &decls[0]));
    return Owned(new DeclStmt(DG, StartLoc, EndLoc));
  }
}

Action::OwningStmtResult
Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
                        MultiStmtArg elts, bool isStmtExpr) {
  unsigned NumElts = elts.size();
  Stmt **Elts = reinterpret_cast<Stmt**>(elts.release());
  // If we're in C89 mode, check that we don't have any decls after stmts.  If
  // so, emit an extension diagnostic.
  if (!getLangOptions().C99 && !getLangOptions().CPlusPlus) {
    // Note that __extension__ can be around a decl.
    unsigned i = 0;
    // Skip over all declarations.
    for (; i != NumElts && isa<DeclStmt>(Elts[i]); ++i)
      /*empty*/;

    // We found the end of the list or a statement.  Scan for another declstmt.
    for (; i != NumElts && !isa<DeclStmt>(Elts[i]); ++i)
      /*empty*/;
    
    if (i != NumElts) {
      ScopedDecl *D = *cast<DeclStmt>(Elts[i])->decl_begin();
      Diag(D->getLocation(), diag::ext_mixed_decls_code);
    }
  }
  // Warn about unused expressions in statements.
  for (unsigned i = 0; i != NumElts; ++i) {
    Expr *E = dyn_cast<Expr>(Elts[i]);
    if (!E) continue;
    
    // Warn about expressions with unused results.
    if (E->hasLocalSideEffect() || E->getType()->isVoidType())
      continue;
    
    // The last expr in a stmt expr really is used.
    if (isStmtExpr && i == NumElts-1)
      continue;
    
    /// DiagnoseDeadExpr - This expression is side-effect free and evaluated in
    /// a context where the result is unused.  Emit a diagnostic to warn about
    /// this.
    if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(E))
      Diag(BO->getOperatorLoc(), diag::warn_unused_expr)
        << BO->getLHS()->getSourceRange() << BO->getRHS()->getSourceRange();
    else if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E))
      Diag(UO->getOperatorLoc(), diag::warn_unused_expr)
        << UO->getSubExpr()->getSourceRange();
    else
      Diag(E->getExprLoc(), diag::warn_unused_expr) << E->getSourceRange();
  }

  return Owned(new CompoundStmt(Elts, NumElts, L, R));
}

Action::OwningStmtResult
Sema::ActOnCaseStmt(SourceLocation CaseLoc, ExprArg lhsval