compilerplugins/clang/dyncastvisibility.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   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
  10 #ifndef LO_CLANG_SHARED_PLUGINS
  11
  12 #include <algorithm>
  13 #include <cassert>
  14 #include <cstddef>
  15 #include <set>
  16 #include <string>
  17
  18 #include "plugin.hxx"
  19
  20 namespace {
  21
  22 using Bases = std::set<CXXRecordDecl const *>;
  23
  24 Visibility getTypeVisibility(CXXRecordDecl const * decl) {
  25     assert(decl->isThisDeclarationADefinition());
  26     if (auto const opt = decl->getExplicitVisibility(
  27             NamedDecl::VisibilityForType))
  28     {
  29         return *opt;
  30     }
  31     if (auto const opt = decl->getExplicitVisibility(
  32             NamedDecl::VisibilityForValue))
  33     {
  34         return *opt;
  35     }
  36     auto const vis = decl->getVisibility();
  37     return vis == DefaultVisibility && decl->isInAnonymousNamespace()
  38         ? HiddenVisibility : vis;
  39 }
  40
  41 // Check whether 'decl' is derived from 'base', gathering any 'bases' between
  42 // 'decl' and 'base', and whether any of those 'bases' or 'base' are 'hidden'
  43 // (i.e., have non-default visibility):
  44 bool isDerivedFrom(
  45     CXXRecordDecl const * decl, CXXRecordDecl const * base, Bases * bases,
  46     bool * hidden)
  47 {
  48     bool derived = false;
  49     for (auto const i: decl->bases()) {
  50         auto const bd
  51             = (cast<CXXRecordDecl>(i.getType()->getAs<RecordType>()->getDecl())
  52                ->getDefinition());
  53         assert(bd != nullptr);
  54         if (bd == base) {
  55             *hidden |= getTypeVisibility(base) != DefaultVisibility;
  56             derived = true;
  57         }
  58         else if (bd->isDerivedFrom(base)) {
  59             if (bases->insert(bd).second) {
  60                 auto const d = isDerivedFrom(bd, base, bases, hidden);
  61                 assert(d);
  62                 (void)d;
  63                 *hidden |= getTypeVisibility(bd) != DefaultVisibility;
  64             }
  65             derived = true;
  66         }
  67     }
  68     return derived;
  69 }
  70
  71 StringRef vis(Visibility v) {
  72     switch (v) {
  73     case HiddenVisibility:
  74         return "hidden";
  75     case ProtectedVisibility:
  76         return "protected";
  77     case DefaultVisibility:
  78         return "default";
  79     }
  80     llvm_unreachable("unknown visibility");
  81 }
  82
  83 class DynCastVisibility final:
  84     public loplugin::FilteringPlugin<DynCastVisibility>
  85 {
  86 public:
  87     explicit DynCastVisibility(loplugin::InstantiationData const & data):
  88         FilteringPlugin(data) {}
  89
  90     bool shouldVisitTemplateInstantiations() const { return true; }
  91
  92     bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
  93         if (ignoreLocation(expr)) {
  94             return true;
  95         }
  96         auto td = expr->getTypeAsWritten();
  97         if (auto const t = td->getAs<ReferenceType>()) {
  98             td = t->getPointeeType();
  99         }
 100         while (auto const t = td->getAs<clang::PointerType>()) {
 101             td = t->getPointeeType();
 102         }
 103         auto const rtd = td->getAs<RecordType>();
 104         if (rtd == nullptr) {
 105             return true;
 106         }
 107         auto const rdd = cast<CXXRecordDecl>(rtd->getDecl())->getDefinition();
 108         assert(rdd != nullptr);
 109         if (getTypeVisibility(rdd) != DefaultVisibility) {
 110             // Heuristic to find problematic dynamic_cast<T> with hidden type T is: T is defined in
 111             // include/M1/ while the compilation unit is in module M2/ with M1 != M2.  There are
 112             // legitimate cases where T is a hidden type in dynamic_cast<T>, e.g., when both the
 113             // type and the cast are in the same library.  This heuristic appears to be conservative
 114             // enough to produce only a few false positives (which have been addressed with
 115             // preceding commits, marking the relevant types in global include files as
 116             // SAL_DLLPUBLIC_RTTI after all, to be on the safe side) and aggressive enough to find
 117             // at least some interesting cases (though it would still not be aggressive enough to
 118             // have found ff570b4b58dbf274d3094d21d974f18b613e9b4b "DocumentSettingsSerializer must
 119             // be SAL_DLLPUBLIC_RTTI for dynamic_cast"):
 120             auto const file = getFilenameOfLocation(
 121                 compiler.getSourceManager().getSpellingLoc(rdd->getLocation()));
 122             if (loplugin::hasPathnamePrefix(file, SRCDIR "/include/")) {
 123                 std::size_t const n1 = std::strlen(SRCDIR "/include/");
 124                 std::size_t n2 = file.find('/', n1);
 125 #if defined _WIN32
 126                 n2 = std::min(n2, file.find('\\', n1));
 127 #endif
 128                 auto const seg = n2 >= file.size() ? file.substr(n1) : file.substr(n1, n2 - n1);
 129                 auto prefix = std::string(SRCDIR "/");
 130                 prefix += seg;
 131                 if (!loplugin::hasPathnamePrefix(
 132                             handler.getMainFileName(), prefix))
 133                 {
 134                     report(
 135                         DiagnosticsEngine::Warning,
 136                         "Suspicious dynamic_cast to %0 with %1 type visibility", expr->getExprLoc())
 137                         << td << vis(getTypeVisibility(rdd)) << expr->getSourceRange();
 138                     report(DiagnosticsEngine::Note, "class %0 defined here", rdd->getLocation())
 139                         << td << rdd->getSourceRange();
 140                 }
 141             }
 142             return true;
 143         }
 144         auto ts = expr->getSubExpr()->getType();
 145         while (auto const t = ts->getAs<clang::PointerType>()) {
 146             ts = t->getPointeeType();
 147         }
 148         auto const rts = ts->getAs<RecordType>();
 149         if (rts == nullptr) { // in case it's a dependent type
 150             return true;
 151         }
 152         auto const rds = cast<CXXRecordDecl>(rts->getDecl())->getDefinition();
 153         assert(rds != nullptr);
 154         Bases bs;
 155         bool hidden = false;
 156         if (!(isDerivedFrom(rdd, rds, &bs, &hidden) && hidden)) {
 157             return true;
 158         }
 159         report(
 160             DiagnosticsEngine::Warning,
 161             ("dynamic_cast from %0 with %1 type visibility to %2 with %3 type"
 162              " visibility"),
 163             expr->getExprLoc())
 164             << ts << vis(getTypeVisibility(rds)) << td
 165             << vis(getTypeVisibility(rdd)) << expr->getSourceRange();
 166         report(
 167             DiagnosticsEngine::Note,
 168             "base class %0 with %1 type visibility defined here",
 169             rds->getLocation())
 170             << ts << vis(getTypeVisibility(rds)) << rds->getSourceRange();
 171         for (auto const i: bs) {
 172             if (getTypeVisibility(i) != DefaultVisibility) {
 173                 report(
 174                     DiagnosticsEngine::Note,
 175                     ("intermediary class %0 with %1 type visibility defined"
 176                      " here"),
 177                     i->getLocation())
 178                     << i << vis(getTypeVisibility(i)) << i->getSourceRange();
 179             }
 180         }
 181         report(
 182             DiagnosticsEngine::Note,
 183             "derived class %0 with %1 type visibility defined here",
 184             rdd->getLocation())
 185             << td << vis(getTypeVisibility(rdd)) << rdd->getSourceRange();
 186         return true;
 187     }
 188
 189     virtual bool preRun() override {
 190         return compiler.getLangOpts().CPlusPlus;
 191     }
 192 private:
 193     void run() override {
 194         if (preRun()) {
 195             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 196         }
 197     }
 198 };
 199
 200 static loplugin::Plugin::Registration<DynCastVisibility> dyncastvisibility(
 201     "dyncastvisibility");
 202
 203 }
 204
 205 #endif // LO_CLANG_SHARED_PLUGINS
 206
 207 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */