1 files changed, 132 insertions, 0 deletions
diff --git a/compilerplugins/clang/store/postfixincrementfix.cxx b/compilerplugins/clang/store/postfixincrementfix.cxx
new file mode 100644
index 000000000..eba6f35b5
--- /dev/null
+++ b/compilerplugins/clang/store/postfixincrementfix.cxx
@@ -0,0 +1,132 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * 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( const InstantiationData& data )
+    : FilteringRewritePlugin( data )
+    {
+    }
+
+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
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */