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/*
* This file is part of the LibreOffice project.
*
* Based on LLVM/Clang.
*
* This file is distributed under the University of Illinois Open Source
* License. See LICENSE.TXT for details.
*
*/
#include "postfixincrementfix.hxx"
/*
This is a rewriter.
Change all postfix ++ operators of non-trivial types to prefix if possible.
*/
namespace loplugin
{
PostfixIncrementFix::PostfixIncrementFix( CompilerInstance& compiler, Rewriter& rewriter )
: RewritePlugin( compiler, rewriter )
{
}
void PostfixIncrementFix::run()
{
TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
}
bool PostfixIncrementFix::VisitCXXOperatorCallExpr( const CXXOperatorCallExpr* op )
{
if( ignoreLocation( op ))
return true;
// postfix ++ has two arguments (the operand and the hidden extra int)
if( op->getOperator() == OO_PlusPlus && op->getNumArgs() == 2 )
fixPostfixOperator( op );
// For primitive types it would be UnaryOperatorExpr, but probably no good reason to change those.
return true;
}
void PostfixIncrementFix::fixPostfixOperator( const CXXOperatorCallExpr* op )
{
if( !canChangePostfixToPrefix( op, op ))
return;
if( !shouldDoChange( op->getArg( 0 )))
return;
// Adding spaces around the moved ++ should not be necessary
// (there might a problem with e.g. a+b++ -> a+++b (i.e. a++ +b),
// but we don't change such expressions).
if( insertText( op->getLocStart(), "++" )) // insert is intentionally first, in case it fails
removeText( op->getCallee()->getSourceRange());
}
bool PostfixIncrementFix::canChangePostfixToPrefix( const Stmt* stmt , const CXXOperatorCallExpr* op )
{
const Stmt* parent = parentStmt( stmt );
if( parent == NULL )
return true;
// check if foo++ can be safely replaced by ++foo
switch( parent->getStmtClass())
{
case Stmt::CompoundStmtClass:
return true;
// these mean somebody is going to use it
case Stmt::ImplicitCastExprClass:
case Stmt::MaterializeTemporaryExprClass:
case Stmt::BinaryOperatorClass:
case Stmt::UnaryOperatorClass:
case Stmt::CallExprClass:
case Stmt::CXXOperatorCallExprClass:
return false;
case Stmt::CXXBindTemporaryExprClass:
// tricky, it may just mean the temporary will be cleaned up
// (by ExprWithCleanups), ignore and go up
return canChangePostfixToPrefix( parent, op );
case Stmt::ExprWithCleanupsClass:
// cleanup of a temporary, should be harmless (if the use
// of the postfix ++ operator here relies on the fact that
// the dtor for the object will be called, that's pretty insane
// code). Ignore and go up.
return canChangePostfixToPrefix( parent, op );
case Stmt::ParenExprClass: // parentheses, go up
return canChangePostfixToPrefix( parent, op );
case Stmt::IfStmtClass:
// cannot be changed in condition, can be changed in statements
return cast< IfStmt >( parent )->getCond() != stmt;
case Stmt::WhileStmtClass:
return cast< WhileStmt >( parent )->getCond() != stmt;
case Stmt::DoStmtClass:
return cast< DoStmt >( parent )->getCond() != stmt;
case Stmt::ForStmtClass:
return cast< ForStmt >( parent )->getCond() != stmt;
default:
report( DiagnosticsEngine::Fatal, "cannot analyze operator++ (plugin needs fixing)",
op->getLocStart()) << parent->getSourceRange();
parent->dump();
return false;
}
}
bool PostfixIncrementFix::shouldDoChange( const Expr* operand )
{
// TODO Changing 'a->b++' to '++a->b' is technically the same, but the latter probably looks confusing,
// so either avoid that, or add parentheses. Avoid for now.
const Expr* expr = const_cast< Expr* >( operand )->IgnoreImplicit(); // does not have const version
switch( expr->getStmtClass())
{
case Stmt::ParenExprClass:
return true; // there are already parentheses, ok to move the ++
case Stmt::MemberExprClass:
return false; // ++a->b , avoid
case Stmt::DeclRefExprClass:
return true;
default:
{
report( DiagnosticsEngine::Fatal, "cannot analyze operator++ (plugin needs fixing)",
expr->getLocStart()) << operand->getSourceRange();
expr->dump();
operand->dump();
return false;
}
}
}
static Plugin::Registration< PostfixIncrementFix > X( "postfixincrementfix" );
} // namespace
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