new loplugin: unusedmethods

Change-Id: I72574e354aadf357d6d8181a514efb4783e79e28

1 files changed, 198 insertions, 0 deletions

diff --git a/compilerplugins/clang/unusedmethods.cxx b/compilerplugins/clang/unusedmethods.cxx
new file mode 100644
index 000000000000..e45ee7fb7fd3
--- /dev/null
+++ b/compilerplugins/clang/unusedmethods.cxx
@@ -0,0 +1,198 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <set>
+#include "plugin.hxx"
+#include "compat.hxx"
+
+/**
+Dump a list of calls to methods, and a list of method definitions.
+Then we will post-process the 2 lists and find the set of unused methods.
+
+Be warned that it produces around 3G of log file.
+
+The process goes something like this:
+  $ make check
+  $ make FORCE_COMPILE_ALL=1 COMPILER_PLUGIN_TOOL='unusedmethods' check > log.txt
+  $ grep -P '(call:)|(definition:)' log.txt | sort -u > log2.txt
+  $ ./compilerplugins/clang/unusedmethods.py log2.txt > result.txt
+
+and then
+  $ for dir in *; do make FORCE_COMPILE_ALL=1 UPDATE_FILES=$dir COMPILER_PLUGIN_TOOL='unusedmethodsremove' $dir; done
+to auto-remove the method declarations
+
+Note that the actual process may involve a fair amount of undoing, hand editing, and general messing around
+to get it to work :-)
+
+TODO ignore calls from a method to itself, so we can eliminate unused recursive methods
+TODO deal with calls to superclass/member constructors from other constructors, so
+     we can find unused constructors
+TODO need to handle places where the code takes the address of a method, that needs to count
+     as a use-site.
+TODO deal with free functions and static methods
+TODO track instantiations of template class constructor methods
+*/
+
+namespace {
+
+class UnusedMethods:
+    public RecursiveASTVisitor<UnusedMethods>, public loplugin::Plugin
+{
+public:
+    explicit UnusedMethods(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitCallExpr(CallExpr* );
+    bool VisitCXXMethodDecl( const CXXMethodDecl* decl );
+    bool VisitDeclRefExpr( const DeclRefExpr* );
+    bool TraverseCXXMethodDecl(CXXMethodDecl * decl) { return RecursiveASTVisitor::TraverseCXXMethodDecl(decl); }
+};
+
+static std::string niceName(const CXXMethodDecl* functionDecl)
+{
+    std::string s =
+        compat::getReturnType(*functionDecl).getCanonicalType().getAsString()
+        + " " + functionDecl->getParent()->getQualifiedNameAsString()
+        + "::" + functionDecl->getNameAsString()
+        + "(";
+    bool bFirst = true;
+    for (const ParmVarDecl *pParmVarDecl : functionDecl->params()) {
+        if (bFirst)
+            bFirst = false;
+        else
+            s += ",";
+        s += pParmVarDecl->getType().getCanonicalType().getAsString();
+    }
+    s += ")";
+    if (functionDecl->isConst()) {
+        s += " const";
+    }
+    return s;
+}
+
+// try to limit the volumninous output a little
+static std::set<std::string> alreadySeenCallSet;
+
+static void logCallToRootMethods(const CXXMethodDecl* decl)
+{
+    // For virtual/overriding methods, we need to pretend we called the root method(s),
+    // so that they get marked as used.
+    bool bPrinted = false;
+    for(CXXMethodDecl::method_iterator it = decl->begin_overridden_methods();
+        it != decl->end_overridden_methods(); ++it)
+    {
+        logCallToRootMethods(*it);
+        bPrinted = true;
+    }
+    if (!bPrinted)
+    {
+        std::string s = niceName(decl);
+        if (alreadySeenCallSet.insert(s).second)
+            cout << "call:\t" << niceName(decl) << endl;
+    }
+}
+
+static bool startsWith(const std::string& s, const char* other)
+{
+    return s.compare(0, strlen(other), other) == 0;
+}
+
+static bool isStandardStuff(const std::string& s)
+{
+    // ignore UNO interface definitions, cannot change those
+    return startsWith(s, "com::sun::star::")
+          // ignore stuff in the C++ stdlib and boost
+          || startsWith(s, "std::") || startsWith(s, "boost::") || startsWith(s, "class boost::") || startsWith(s, "__gnu_debug::")
+          // can't change our rtl layer
+          || startsWith(s, "rtl::")
+          // ignore anonymous namespace stuff, it is compilation-unit-local and the compiler will detect any
+          // unused code there
+          || startsWith(s, "(anonymous namespace)::");
+}
+
+bool UnusedMethods::VisitCallExpr(CallExpr* expr)
+{
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    CXXMethodDecl* decl = dyn_cast_or_null<CXXMethodDecl>(
+        expr->getDirectCallee());
+    if (decl == nullptr) {
+        return true;
+    }
+    logCallToRootMethods(decl);
+    // if we see a call to a templated method, it effectively instantiates a new method,
+    // so we need to examine it's interior to see if it in turn calls anything else
+    if (decl->getTemplatedKind() != clang::FunctionDecl::TemplatedKind::TK_NonTemplate
+        || decl->isFunctionTemplateSpecialization())
+    {
+        TraverseCXXMethodDecl(decl);
+    }
+    return true;
+}
+
+bool UnusedMethods::VisitCXXMethodDecl( const CXXMethodDecl* functionDecl )
+{
+    if (ignoreLocation(functionDecl)) {
+        return true;
+    }
+    functionDecl = functionDecl->getCanonicalDecl();
+    // ignore method overrides, since the call will show up as being directed to the root method
+    if (functionDecl->size_overridden_methods() != 0 || functionDecl->hasAttr<OverrideAttr>()) {
+        return true;
+    }
+    // ignore static's for now. Would require generalising this plugin a little
+    if (functionDecl->isStatic()) {
+        return true;
+    }
+    // ignore stuff that forms part of the stable URE interface
+    if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(
+                              functionDecl->getNameInfo().getLoc()))) {
+        return true;
+    }
+    if (isStandardStuff(functionDecl->getParent()->getQualifiedNameAsString())) {
+        return true;
+    }
+    if (isa<CXXDestructorDecl>(functionDecl)) {
+        return true;
+    }
+    if (isa<CXXConstructorDecl>(functionDecl)) {
+        return true;
+    }
+    if (functionDecl->isDeleted()) {
+        return true;
+    }
+
+    cout << "definition:\t" << niceName(functionDecl) << endl;
+    return true;
+}
+
+// this catches places that take the address of a method
+bool UnusedMethods::VisitDeclRefExpr( const DeclRefExpr* declRefExpr )
+{
+    if (ignoreLocation(declRefExpr)) {
+        return true;
+    }
+    const Decl* functionDecl = declRefExpr->getDecl();
+    if (!isa<CXXMethodDecl>(functionDecl)) {
+        return true;
+    }
+    logCallToRootMethods(dyn_cast<CXXMethodDecl>(functionDecl));
+    return true;
+}
+
+loplugin::Plugin::Registration< UnusedMethods > X("unusedmethods", false);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */