compilerplugins/clang/stringview.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9 #ifndef LO_CLANG_SHARED_PLUGINS
  10
  11 #include <cassert>
  12 #include <string>
  13 #include <iostream>
  14 #include <unordered_map>
  15 #include <unordered_set>
  16
  17 #include "plugin.hxx"
  18 #include "check.hxx"
  19 #include "clang/AST/CXXInheritance.h"
  20 #include "clang/AST/StmtVisitor.h"
  21
  22 /**
  23     Look for places where we are making a substring copy of an OUString, and then passing it to a
  24     function that takes a u16string_view, in which case it is more efficient to pass a view
  25     of the OUString, rather than making a copy.
  26
  27     TODO currently does not check if there is some other visible overload of the callee, that can take
  28     a string_view.
  29     TODO handle OUStringBuffer/OStringBuffer similarly
  30 */
  31
  32 namespace
  33 {
  34 class StringView : public loplugin::FilteringPlugin<StringView>
  35 {
  36 public:
  37     explicit StringView(loplugin::InstantiationData const& data)
  38         : FilteringPlugin(data)
  39     {
  40     }
  41
  42     bool preRun() override { return true; }
  43
  44     virtual void run() override
  45     {
  46         if (!preRun())
  47             return;
  48         TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  49     }
  50
  51     bool VisitFunctionDecl(FunctionDecl const*);
  52     bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const*);
  53     bool VisitImplicitCastExpr(ImplicitCastExpr const*);
  54
  55 private:
  56     void handleCXXConstructExpr(CXXConstructExpr const* expr);
  57     void handleCXXMemberCallExpr(CXXMemberCallExpr const* expr);
  58 };
  59
  60 bool StringView::VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* cxxOperatorCallExpr)
  61 {
  62     if (ignoreLocation(cxxOperatorCallExpr))
  63         return true;
  64
  65     auto check = [&](const Expr* expr) -> void {
  66         auto memberCallExpr = dyn_cast<CXXMemberCallExpr>(compat::IgnoreImplicit(expr));
  67         if (!memberCallExpr)
  68             return;
  69         auto methodDecl = memberCallExpr->getMethodDecl();
  70         if (!methodDecl->getIdentifier() || methodDecl->getName() != "copy")
  71             return;
  72         report(DiagnosticsEngine::Warning, "rather than copy, pass with a view using subView()",
  73                compat::getBeginLoc(expr))
  74             << expr->getSourceRange();
  75     };
  76     auto op = cxxOperatorCallExpr->getOperator();
  77     if (op == OO_Plus && cxxOperatorCallExpr->getNumArgs() == 2)
  78     {
  79         check(cxxOperatorCallExpr->getArg(0));
  80         check(cxxOperatorCallExpr->getArg(1));
  81     }
  82     if (compat::isComparisonOp(cxxOperatorCallExpr))
  83     {
  84         check(cxxOperatorCallExpr->getArg(0));
  85         check(cxxOperatorCallExpr->getArg(1));
  86     }
  87     else if (op == OO_PlusEqual)
  88         check(cxxOperatorCallExpr->getArg(1));
  89     else if (op == OO_Subscript)
  90         check(cxxOperatorCallExpr->getArg(0));
  91     return true;
  92 }
  93
  94 bool StringView::VisitFunctionDecl(FunctionDecl const* functionDecl)
  95 {
  96     if (ignoreLocation(functionDecl))
  97         return true;
  98     // debugging
  99     // if (functionDecl->getIdentifier() && functionDecl->getName() == "f1")
 100     //     functionDecl->dump();
 101     return true;
 102 }
 103
 104 bool StringView::VisitImplicitCastExpr(ImplicitCastExpr const* expr)
 105 {
 106     if (ignoreLocation(expr))
 107     {
 108         return true;
 109     }
 110     if (!loplugin::TypeCheck(expr->getType()).ClassOrStruct("basic_string_view").StdNamespace())
 111     {
 112         return true;
 113     }
 114     auto const e = expr->getSubExprAsWritten()->IgnoreParens();
 115     auto const tc = loplugin::TypeCheck(e->getType());
 116     if (!(tc.Class("OString").Namespace("rtl").GlobalNamespace()
 117           || tc.Class("OUString").Namespace("rtl").GlobalNamespace()))
 118     {
 119         return true;
 120     }
 121     if (auto const e1 = dyn_cast<CXXConstructExpr>(e))
 122     {
 123         handleCXXConstructExpr(e1);
 124     }
 125     else if (auto const e2 = dyn_cast<CXXMemberCallExpr>(e))
 126     {
 127         handleCXXMemberCallExpr(e2);
 128     }
 129     return true;
 130 }
 131
 132 void StringView::handleCXXConstructExpr(CXXConstructExpr const* expr)
 133 {
 134     if (expr->getNumArgs() != 0)
 135     {
 136         return;
 137     }
 138     report(DiagnosticsEngine::Warning,
 139            "instead of an empty %0, pass an empty '%select{std::string_view|std::u16string_view}1'",
 140            expr->getExprLoc())
 141         << expr->getType()
 142         << (loplugin::TypeCheck(expr->getType()).Class("OString").Namespace("rtl").GlobalNamespace()
 143                 ? 0
 144                 : 1)
 145         << expr->getSourceRange();
 146 }
 147
 148 void StringView::handleCXXMemberCallExpr(CXXMemberCallExpr const* expr)
 149 {
 150     auto const dc = loplugin::DeclCheck(expr->getMethodDecl()).Function("copy");
 151     if (!dc)
 152     {
 153         return;
 154     }
 155     if (!(dc.Class("OString").Namespace("rtl").GlobalNamespace()
 156           || dc.Class("OUString").Namespace("rtl").GlobalNamespace()))
 157     {
 158         return;
 159     }
 160     report(DiagnosticsEngine::Warning, "rather than copy, pass with a view using subView()",
 161            expr->getExprLoc())
 162         << expr->getSourceRange();
 163 }
 164
 165 loplugin::Plugin::Registration<StringView> stringview("stringview");
 166 }
 167
 168 #endif // LO_CLANG_SHARED_PLUGINS
 169
 170 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */