new loplugin: singlevalfields

look for fields that only have a single constant value assigned to them

Change-Id: Iafcd37fdb8a8119bbc00f92981a1a01badf9c5a2

3 files changed, 481 insertions, 2 deletions

diff --git a/compilerplugins/clang/constantparam.cxx b/compilerplugins/clang/constantparam.cxx
index 99db54554dbd..54fe00c7477e 100644
--- a/compilerplugins/clang/constantparam.cxx
+++ b/compilerplugins/clang/constantparam.cxx
@@ -16,8 +16,7 @@
 #include "compat.hxx"
 
 /*
- Find methods with default params, where the callers never specify the default param i.e.
- might as well remove it.
+  Find params on methods where the param is only ever passed as a single constant value.
 
  The process goes something like this:
   $ make check
diff --git a/compilerplugins/clang/singlevalfields.cxx b/compilerplugins/clang/singlevalfields.cxx
new file mode 100644
index 000000000000..b1c7cc80254c
--- /dev/null
+++ b/compilerplugins/clang/singlevalfields.cxx
@@ -0,0 +1,411 @@
+/* -*- 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 <fstream>
+#include <set>
+#include "plugin.hxx"
+#include "compat.hxx"
+
+/**
+Look for fields that are only ever assigned a single constant value.
+
+We dmp a list of values assigned to fields, and a list of field definitions.
+Then we will post-process the 2 lists and find the set of interesting fields.
+
+Be warned that it produces around 5G of log file.
+
+The process goes something like this:
+  $ make check
+  $ make FORCE_COMPILE_ALL=1 COMPILER_PLUGIN_TOOL='singlevalfields' check
+  $ ./compilerplugins/clang/singlevalfields.py
+
+Note that the actual process may involve a fair amount of undoing, hand editing, and general messing around
+to get it to work :-)
+
+@TODO we don't spot fields that have been zero-initialised via calloc or rtl_allocateZeroMemory
+
+*/
+
+namespace {
+
+struct MyFieldInfo
+{
+    std::string parentClass;
+    std::string fieldName;
+    std::string sourceLocation;
+};
+bool operator < (const MyFieldInfo &lhs, const MyFieldInfo &rhs)
+{
+    return std::tie(lhs.parentClass, lhs.fieldName)
+         < std::tie(rhs.parentClass, rhs.fieldName);
+}
+
+struct MyFieldAssignmentInfo : public MyFieldInfo
+{
+    std::string value;
+};
+
+bool operator < (const MyFieldAssignmentInfo &lhs, const MyFieldAssignmentInfo &rhs)
+{
+    return std::tie(lhs.parentClass, lhs.fieldName, lhs.value)
+         < std::tie(rhs.parentClass, rhs.fieldName, rhs.value);
+}
+
+
+// try to limit the voluminous output a little
+static std::set<MyFieldAssignmentInfo> assignedSet;
+static std::set<MyFieldInfo> definitionSet;
+
+
+class SingleValFields:
+    public RecursiveASTVisitor<SingleValFields>, public loplugin::Plugin
+{
+public:
+    explicit SingleValFields(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+
+        // dump all our output in one write call - this is to try and limit IO "crosstalk" between multiple processes
+        // writing to the same logfile
+        std::string output;
+        for (const MyFieldAssignmentInfo & s : assignedSet)
+            output += "asgn:\t" + s.parentClass + "\t" + s.fieldName + "\t" + s.value + "\n";
+        for (const MyFieldInfo & s : definitionSet)
+            output += "defn:\t" + s.parentClass + "\t" + s.fieldName + "\t" + s.sourceLocation + "\n";
+        ofstream myfile;
+        myfile.open( SRCDIR "/singlevalfields.log", ios::app | ios::out);
+        myfile << output;
+        myfile.close();
+    }
+
+    bool shouldVisitTemplateInstantiations () const { return true; }
+
+    bool VisitFieldDecl( const FieldDecl* );
+    bool VisitMemberExpr( const MemberExpr* );
+    bool VisitCXXConstructorDecl( const CXXConstructorDecl* );
+private:
+    void niceName(const FieldDecl*, MyFieldInfo&);
+    std::string fullyQualifiedName(const FunctionDecl*);
+    std::string getExprValue(const Expr*);
+    bool isInterestingType(const QualType&);
+    const FunctionDecl* get_top_FunctionDecl_from_Stmt(const Stmt&);
+};
+
+void SingleValFields::niceName(const FieldDecl* fieldDecl, MyFieldInfo& aInfo)
+{
+    aInfo.parentClass = fieldDecl->getParent()->getQualifiedNameAsString();
+    aInfo.fieldName = fieldDecl->getNameAsString();
+
+    SourceLocation expansionLoc = compiler.getSourceManager().getExpansionLoc( fieldDecl->getLocation() );
+    StringRef name = compiler.getSourceManager().getFilename(expansionLoc);
+    aInfo.sourceLocation = std::string(name.substr(strlen(SRCDIR)+1)) + ":" + std::to_string(compiler.getSourceManager().getSpellingLineNumber(expansionLoc));
+}
+
+std::string SingleValFields::fullyQualifiedName(const FunctionDecl* functionDecl)
+{
+    std::string ret = compat::getReturnType(*functionDecl).getCanonicalType().getAsString();
+    ret += " ";
+    if (isa<CXXMethodDecl>(functionDecl)) {
+        const CXXRecordDecl* recordDecl = dyn_cast<CXXMethodDecl>(functionDecl)->getParent();
+        ret += recordDecl->getQualifiedNameAsString();
+        ret += "::";
+    }
+    ret += functionDecl->getNameAsString() + "(";
+    bool bFirst = true;
+    for (const ParmVarDecl *pParmVarDecl : functionDecl->params()) {
+        if (bFirst)
+            bFirst = false;
+        else
+            ret += ",";
+        ret += pParmVarDecl->getType().getCanonicalType().getAsString();
+    }
+    ret += ")";
+    if (isa<CXXMethodDecl>(functionDecl) && dyn_cast<CXXMethodDecl>(functionDecl)->isConst()) {
+        ret += " const";
+    }
+
+    return ret;
+}
+
+bool SingleValFields::VisitFieldDecl( const FieldDecl* fieldDecl )
+{
+    fieldDecl = fieldDecl->getCanonicalDecl();
+    const FieldDecl* canonicalDecl = fieldDecl;
+
+    if( ignoreLocation( fieldDecl ) || !isInterestingType(fieldDecl->getType()) )
+        return true;
+
+    MyFieldInfo aInfo;
+    niceName(canonicalDecl, aInfo);
+    definitionSet.insert(aInfo);
+    return true;
+}
+
+bool SingleValFields::VisitCXXConstructorDecl( const CXXConstructorDecl* decl )
+{
+    if( ignoreLocation( decl ) )
+        return true;
+
+    // doesn't count as a write to fields because it's self->self
+    if (decl->isCopyOrMoveConstructor())
+            return true;
+
+    for(auto it = decl->init_begin(); it != decl->init_end(); ++it)
+    {
+        const CXXCtorInitializer* init = *it;
+        const FieldDecl* fieldDecl = init->getMember();
+        if( !fieldDecl || !isInterestingType(fieldDecl->getType()) )
+            continue;
+        MyFieldAssignmentInfo aInfo;
+        niceName(fieldDecl, aInfo);
+        aInfo.value = getExprValue(init->getInit());
+        assignedSet.insert(aInfo);
+    }
+    return true;
+}
+
+const Decl* get_DeclContext_from_Stmt(ASTContext& context, const Stmt& stmt)
+{
+  auto it = context.getParents(stmt).begin();
+
+  if (it == context.getParents(stmt).end())
+      return nullptr;
+
+  const Decl *aDecl = it->get<Decl>();
+  if (aDecl)
+      return aDecl;
+
+  const Stmt *aStmt = it->get<Stmt>();
+  if (aStmt)
+      return get_DeclContext_from_Stmt(context, *aStmt);
+
+  return nullptr;
+}
+
+const FunctionDecl* SingleValFields::get_top_FunctionDecl_from_Stmt(const Stmt& stmt)
+{
+  const Decl *decl = get_DeclContext_from_Stmt(compiler.getASTContext(), stmt);
+  if (decl)
+      return static_cast<const FunctionDecl*>(decl->getNonClosureContext());
+
+  return nullptr;
+}
+
+
+bool SingleValFields::VisitMemberExpr( const MemberExpr* memberExpr )
+{
+    const ValueDecl* decl = memberExpr->getMemberDecl();
+    const FieldDecl* fieldDecl = dyn_cast<FieldDecl>(decl);
+    if (!fieldDecl) {
+        return true;
+    }
+
+    if (ignoreLocation(memberExpr) || !isInterestingType(fieldDecl->getType()))
+        return true;
+
+    const CXXMethodDecl* methodDecl = dyn_cast_or_null<CXXMethodDecl>(get_top_FunctionDecl_from_Stmt(*memberExpr));
+    if (methodDecl && (methodDecl->isCopyAssignmentOperator() || methodDecl->isMoveAssignmentOperator()
+                       || dyn_cast<CXXDestructorDecl>(methodDecl)))
+       return true;
+
+    // walk up the tree until we find something interesting
+    const Stmt* child = memberExpr;
+    const Stmt* parent = parentStmt(memberExpr);
+    bool bPotentiallyAssignedTo = false;
+    bool bDump = false;
+    std::string assignValue;
+    do {
+        // check for field being accessed by a reference variable e.g. Foo& f = m.foo;
+        auto parentsList = compiler.getASTContext().getParents(*child);
+        auto it = parentsList.begin();
+        if (it != parentsList.end()) {
+            const VarDecl *varDecl = it->get<VarDecl>();
+            if (varDecl) {
+                QualType qt = varDecl->getType().getDesugaredType(compiler.getASTContext());
+                if (!qt.isConstQualified() && qt->isReferenceType()) {
+                    assignValue = "?";
+                    bPotentiallyAssignedTo = true;
+                    break;
+                }
+            }
+        }
+
+        if (!parent) {
+            return true;
+        }
+        if (isa<CastExpr>(parent) || isa<MemberExpr>(parent) || isa<ParenExpr>(parent) || isa<ParenListExpr>(parent)
+             || isa<ExprWithCleanups>(parent))
+        {
+            child = parent;
+            parent = parentStmt(parent);
+        }
+        else if (isa<UnaryOperator>(parent))
+        {
+            const UnaryOperator* unaryOperator = dyn_cast<UnaryOperator>(parent);
+            int x = unaryOperator->getOpcode();
+            if (x == UO_AddrOf || x == UO_PostInc || x == UO_PostDec || x == UO_PreInc || x == UO_PreDec) {
+                assignValue = "?";
+                bPotentiallyAssignedTo = true;
+                break;
+            }
+            child = parent;
+            parent = parentStmt(parent);
+        }
+        else if (isa<CallExpr>(parent))
+        {
+            const CallExpr* callExpr = dyn_cast<CallExpr>(parent);
+            if (callExpr->getCallee() == child) {
+                break;
+            }
+            const FunctionDecl* functionDecl;
+            if (isa<CXXMemberCallExpr>(callExpr)) {
+                functionDecl = dyn_cast<CXXMemberCallExpr>(callExpr)->getMethodDecl();
+            }
+            else {
+                functionDecl = callExpr->getDirectCallee();
+            }
+            if (!functionDecl) {
+                break;
+            }
+            bool bFound = false;
+            for (unsigned i = 0; i < callExpr->getNumArgs(); ++i) {
+                if (i >= functionDecl->getNumParams()) // can happen in template code
+                    break;
+                if (callExpr->getArg(i) == child) {
+                    const ParmVarDecl* parmVarDecl = functionDecl->getParamDecl(i);
+                    QualType qt = parmVarDecl->getType().getDesugaredType(compiler.getASTContext());
+                    if (!qt.isConstQualified() && qt->isReferenceType()) {
+                        assignValue = "?";
+                        bPotentiallyAssignedTo = true;
+                    }
+                    bFound = true;
+                    break;
+                }
+            }
+            break;
+        }
+        else if (isa<CXXConstructExpr>(parent))
+        {
+            const CXXConstructExpr* consExpr = dyn_cast<CXXConstructExpr>(parent);
+            const CXXConstructorDecl* consDecl = consExpr->getConstructor();
+            bool bFound = false;
+            for (unsigned i = 0; i < consExpr->getNumArgs(); ++i) {
+                if (i >= consDecl->getNumParams()) // can happen in template code
+                    break;
+                if (consExpr->getArg(i) == child) {
+                    const ParmVarDecl* parmVarDecl = consDecl->getParamDecl(i);
+                    QualType qt = parmVarDecl->getType().getDesugaredType(compiler.getASTContext());
+                    if (!qt.isConstQualified() && qt->isReferenceType()) {
+                        assignValue = "?";
+                        bPotentiallyAssignedTo = true;
+                    }
+                    bFound = true;
+                    break;
+                }
+            }
+            break;
+        }
+        else if (isa<BinaryOperator>(parent))
+        {
+            const BinaryOperator* binaryOp = dyn_cast<BinaryOperator>(parent);
+            if ( binaryOp->getLHS() != child ) {
+                // do nothing
+            }
+            else if ( binaryOp->getOpcode() == BO_Assign ) {
+                assignValue = getExprValue(binaryOp->getRHS());
+                bPotentiallyAssignedTo = true;
+            } else {
+                assignValue = "?";
+                bPotentiallyAssignedTo = true;
+            }
+            break;
+        }
+        else if ( isa<CompoundStmt>(parent)
+                || isa<SwitchStmt>(parent) || isa<CaseStmt>(parent) || isa<DefaultStmt>(parent)
+                || isa<DoStmt>(parent) || isa<WhileStmt>(parent)
+                || isa<IfStmt>(parent)
+                || isa<ForStmt>(parent)
+                || isa<ReturnStmt>(parent)
+                || isa<CXXNewExpr>(parent)
+                || isa<CXXDeleteExpr>(parent)
+                || isa<ConditionalOperator>(parent)
+                || isa<CXXTypeidExpr>(parent)
+                || isa<ArraySubscriptExpr>(parent)
+                || isa<CXXDependentScopeMemberExpr>(parent)
+                || isa<DeclStmt>(parent)
+                || isa<UnaryExprOrTypeTraitExpr>(parent)
+                || isa<UnresolvedMemberExpr>(parent)
+                || isa<MaterializeTemporaryExpr>(parent)  //???
+                || isa<InitListExpr>(parent)
+                || isa<CXXUnresolvedConstructExpr>(parent)
+                )
+        {
+            break;
+        }
+        else {
+            bPotentiallyAssignedTo = true;
+            bDump = true;
+            break;
+        }
+    } while (true);
+    if (bDump)
+    {
+        report(
+             DiagnosticsEngine::Warning,
+             "oh dear, what can the matter be?",
+              memberExpr->getLocStart())
+              << memberExpr->getSourceRange();
+        parent->dump();
+    }
+    if (bPotentiallyAssignedTo)
+    {
+        MyFieldAssignmentInfo aInfo;
+        niceName(fieldDecl, aInfo);
+        aInfo.value = assignValue;
+        assignedSet.insert(aInfo);
+    }
+
+    return true;
+}
+
+bool SingleValFields::isInterestingType(const QualType& qt) {
+   return qt.isCXX11PODType(compiler.getASTContext());
+}
+
+std::string SingleValFields::getExprValue(const Expr* arg)
+{
+    if (!arg)
+        return "?";
+    arg = arg->IgnoreParenCasts();
+//    arg->dump();
+    // workaround bug in clang
+    if (isa<ParenListExpr>(arg))
+        return "?";
+    // ignore this, it seems to trigger an infinite recursion
+    if (isa<UnaryExprOrTypeTraitExpr>(arg)) {
+        return "?";
+    }
+    APSInt x1;
+    if (arg->EvaluateAsInt(x1, compiler.getASTContext()))
+    {
+        return x1.toString(10);
+    }
+    return "?";
+}
+
+loplugin::Plugin::Registration< SingleValFields > X("singlevalfields", false);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/compilerplugins/clang/singlevalfields.py b/compilerplugins/clang/singlevalfields.py
new file mode 100755
index 000000000000..523ffa5520f2
--- /dev/null
+++ b/compilerplugins/clang/singlevalfields.py
@@ -0,0 +1,69 @@
+#!/usr/bin/python
+
+import sys
+import re
+import io
+
+definitionToSourceLocationMap = dict() # dict of tuple(parentClass, fieldName) to sourceLocation
+fieldAssignDict = dict() # dict of tuple(parentClass, fieldName) to (set of values)
+
+# clang does not always use exactly the same numbers in the type-parameter vars it generates
+# so I need to substitute them to ensure we can match correctly.
+normalizeTypeParamsRegex = re.compile(r"type-parameter-\d+-\d+")
+def normalizeTypeParams( line ):
+    return normalizeTypeParamsRegex.sub("type-parameter-?-?", line)
+
+# reading as binary (since we known it is pure ascii) is much faster than reading as unicode
+with io.open("singlevalfields.log", "rb", buffering=1024*1024) as txt:
+    for line in txt:
+        if line.startswith("defn:\t"):
+            idx1 = line.find("\t")
+            idx2 = line.find("\t",idx1+1)
+            idx3 = line.find("\t",idx2+1)
+            parentClass = normalizeTypeParams(line[idx1+1:idx2])
+            fieldName = normalizeTypeParams(line[idx2+1:idx3])
+            sourceLocation = line[idx3+1:].strip()
+            fieldInfo = (parentClass, fieldName)
+            definitionToSourceLocationMap[fieldInfo] = sourceLocation
+        elif line.startswith("asgn:\t"):
+            idx1 = line.find("\t")
+            idx2 = line.find("\t",idx1+1)
+            idx3 = line.find("\t",idx2+1)
+            parentClass = normalizeTypeParams(line[idx1+1:idx2])
+            fieldName = normalizeTypeParams(line[idx2+1:idx3])
+            assignValue = line[idx3+1:].strip()
+            fieldInfo = (parentClass, fieldName)
+            if not fieldInfo in fieldAssignDict:
+                fieldAssignDict[fieldInfo] = set()
+            fieldAssignDict[fieldInfo].add(assignValue)
+
+tmp1list = list()
+for fieldInfo, assignValues in fieldAssignDict.iteritems():
+    if len(assignValues) != 1:
+        continue
+    if "?" in assignValues:
+        continue
+    # if it contains anything other than this set, ignore it
+    if len(assignValues - set(["0", "1", "-1", "nullptr"])) > 0:
+        continue
+    v0 = fieldInfo[0] + " " + fieldInfo[1]
+    v1 = (",".join(assignValues))
+    v2 = ""
+    if fieldInfo in definitionToSourceLocationMap:
+        v2 = definitionToSourceLocationMap[fieldInfo]
+    tmp1list.append((v0,v1,v2))
+
+# sort results by filename:lineno
+def natural_sort_key(s, _nsre=re.compile('([0-9]+)')):
+    return [int(text) if text.isdigit() else text.lower()
+            for text in re.split(_nsre, s)]
+tmp1list.sort(key=lambda v: natural_sort_key(v[2]))
+
+# print out the results
+with open("loplugin.singlevalfields", "wt") as f:
+    for v in tmp1list:
+        f.write(v[2] + "\n")
+        f.write("    " + v[0] + "\n")
+        f.write("    " + v[1] + "\n")
+
+