'generic' compiler plugin to modify calls to a specific function

Change-Id: I60756d9054dfa5c55aeae8ddc904ddf6d67d2088

compilerplugins/clang/store/changefunctioncalls.cxx

+/*
+ * 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.
+ *
+ */
+
+/*
+This is a rewriter.
+
+Changes all calls to a specific function (after it's been renamed or its
+arguments have changed).
+
+This specific example checks for calls to function 'void bar(unsigned int)'
+and adds '+ 10' to the argument (as plain text, so if the argument is a more
+complex expression, operator precedence may mean the result is actually different).
+
+This can be easily adjusted for different modifications to a function:
+- replace CallExpr with CXXOperatorCallExpr or CXXMemberCallExpr
+- check different names or arguments
+- etc.
+*/
+
+#include "plugin.hxx"
+
+namespace loplugin
+{
+
+class ChangeFunctionCalls
+    : public RecursiveASTVisitor< ChangeFunctionCalls >
+    , public RewritePlugin
+    {
+    public:
+        explicit ChangeFunctionCalls( CompilerInstance& compiler, Rewriter& rewriter );
+        virtual void run() override;
+        bool VisitCallExpr( const CallExpr* call );
+    };
+
+ChangeFunctionCalls::ChangeFunctionCalls( CompilerInstance& compiler, Rewriter& rewriter )
+    : RewritePlugin( compiler, rewriter )
+    {
+    }
+
+void ChangeFunctionCalls::run()
+    {
+    TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+bool ChangeFunctionCalls::VisitCallExpr( const CallExpr* call )
+    {
+    if( ignoreLocation( call ))
+        return true;
+    if( const FunctionDecl* func = call->getDirectCallee())
+        {
+        // Optimize, getQualifiedNameAsString() is reportedly expensive,
+        // so first check fast details like number of arguments or the (unqualified)
+        // name before checking the fully qualified name.
+        // See FunctionDecl for all the API about the function.
+        if( func->getNumParams() == 1 && func->getIdentifier() != NULL
+            && ( func->getName() == "bar" ))
+            {
+            string qualifiedName = func->getQualifiedNameAsString();
+            if( qualifiedName == "bar" )
+                {
+                // Further checks about arguments. Check mainly ParmVarDecl, VarDecl,
+                // ValueDecl and QualType for Clang API details.
+                string arg0 = func->getParamDecl( 0 )->getType().getAsString();
+                if( arg0 == "unsigned int" )
+                    {
+                    insertTextAfterToken( call->getArg( 0 )->getLocEnd(), " + 10" );
+                    report( DiagnosticsEngine::Warning, "found", call->getLocStart());
+                    }
+                }
+            }
+        }
+    return true;
+    }
+
+static Plugin::Registration< ChangeFunctionCalls > X( "changefunctioncalls" );
+
+} // namespace