also look for cascading assignments

Change-Id: I7fa18403698530eec379589c76631f0aa367b215
Reviewed-on: https://gerrit.libreoffice.org/12991
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>

compilerplugins/clang/store/cascadingassignop.cxx

@@ -0,0 +1,94 @@
+/* -*- 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 "cascadingassignop.hxx"
+
+/*
+This is a compile check.
+
+It checks for complex statements with conditional operators in conditional
+operators, which are errorprone, e.g.
+ Thing foo = IsBar() ? ( IsBaz() ? b1 : b2 ) : b3;
+
+However, it finds 556 cases in sw/source alone, thus likely needs some more
+restricting, e.g. by checking for multiline conditional operator statements or
+a certain length in characters (but that needs the Context/SourceManager, which
+I havent played with yet).
+*/
+
+// the value is rather arbitrary, but code above this number of stmts begins to
+// be smelly
+static const int stmtlimit = 20;
+
+namespace loplugin
+{
+
+struct WalkCounter
+{
+    int  stmtcount;
+    bool cascading;
+    bool conditionals;
+};
+
+// Ctor, nothing special, pass the argument(s).
+CascadingAssignOp::CascadingAssignOp( const InstantiationData& data )
+    : Plugin( data )
+{
+}
+
+// Perform the actual action.
+void CascadingAssignOp::run()
+{
+    // Traverse the whole AST of the translation unit (i.e. examine the whole source file).
+    // The Clang AST helper class will call VisitReturnStmt for every return statement.
+    TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
+}
+
+void CascadingAssignOp::Walk( const Stmt* stmt, WalkCounter& c )
+{
+    for(Stmt::const_child_iterator it = stmt->child_begin(); it != stmt->child_end(); ++it)
+    {
+        ++c.stmtcount;
+        const BinaryOperator* binop = dyn_cast< BinaryOperator >( *it );
+        if ( binop )
+        {
+            if ( (binop->isAssignmentOp() || binop->isCompoundAssignmentOp()))
+                c.cascading = true;
+            if ( dyn_cast< AbstractConditionalOperator >( binop ) || binop->isLogicalOp())
+                c.conditionals = true;
+        }
+        Walk(*it, c);
+    }
+}
+
+bool CascadingAssignOp::VisitStmt( const Stmt* stmt )
+{
+    const BinaryOperator* binop = dyn_cast< BinaryOperator >( stmt );
+    if ( binop && (binop->isAssignmentOp() || binop->isCompoundAssignmentOp()))
+    {
+        WalkCounter c = { 0, false, false };
+        Walk(binop, c);
+        if(c.cascading && c.conditionals && c.stmtcount >= stmtlimit)
+        {
+            std::string msg("cascading assign operator mixing in conditionals, complexity: ");
+            msg.append(std::to_string(c.stmtcount));
+            report( DiagnosticsEngine::Warning, msg, binop->getLocStart());
+        }
+    }
+    return true;
+}
+
+// Register the plugin action with the LO plugin handling.
+static Plugin::Registration< CascadingAssignOp > X( "cascadingassignop" );
+
+} // namespace loplugin
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */

compilerplugins/clang/store/cascadingassignop.hxx

@@ -0,0 +1,40 @@
+/* -*- 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.
+ *
+ */
+
+#ifndef CASCADINGCONDOP_H
+#define CASCADINGCONDOP_H
+
+#include "plugin.hxx"
+
+namespace loplugin
+{
+
+struct WalkCounter;
+
+// The class implementing the plugin action.
+class CascadingAssignOp
+    // Inherits from the Clang class that will allow examing the Clang AST tree (i.e. syntax tree).
+    : public RecursiveASTVisitor< CascadingAssignOp >
+    // And the base class for LO Clang plugins.
+    , public Plugin
+    {
+    public:
+        CascadingAssignOp( const InstantiationData& data );
+        virtual void run() override;
+        void Walk( const Stmt* stmt, WalkCounter& c );
+        bool VisitStmt( const Stmt* stmt );
+    };
+
+} // namespace loplugin
+
+#endif // CASCADINGCONDOP_H
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */