compilerplugins/clang/classmemaccess.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 "check.hxx"
  13 #include "plugin.hxx"
  14
  15 // Similar to GCC "warning: ‘void* memset(void*, int, size_t)’ writing to an object of non-trivial
  16 // type ‘...’; use assignment instead [-Wclass-memaccess]", but looking through toplevel cast to
  17 // void* and taking arrays into account in addition to pointers.  (Clang has
  18 // -Wdynamic-class-memaccess, but that only warns about memset overwriting a vtable pointer.  GCC
  19 // deliberately does not warn when there is a toplevel cast to void*, see
  20 // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81327> "[8 Regression] cast to void* does not
  21 // suppress -Wclass-memaccess".)
  22
  23 namespace
  24 {
  25 class ClassMemAccess final : public loplugin::FilteringPlugin<ClassMemAccess>
  26 {
  27 public:
  28     explicit ClassMemAccess(loplugin::InstantiationData const& data)
  29         : FilteringPlugin(data)
  30     {
  31     }
  32
  33     bool VisitCallExpr(CallExpr const* expr)
  34     {
  35         if (ignoreLocation(expr))
  36         {
  37             return true;
  38         }
  39         auto const fdecl = expr->getDirectCallee();
  40         if (fdecl == nullptr)
  41         {
  42             return true;
  43         }
  44         auto dc = loplugin::DeclCheck(fdecl).Function("memset");
  45         if (!(dc.GlobalNamespace() || dc.StdNamespace()))
  46         {
  47             return true;
  48         }
  49         if (expr->getNumArgs() != 3)
  50         {
  51             if (isDebugMode())
  52             {
  53                 report(DiagnosticsEngine::Fatal,
  54                        "unexpected call to %0 with %1 instead of 3 arguments", expr->getExprLoc())
  55                     << fdecl << expr->getNumArgs() << expr->getSourceRange();
  56                 report(DiagnosticsEngine::Note, "%0 declared here", fdecl->getLocation())
  57                     << fdecl << fdecl->getSourceRange();
  58             }
  59             return true;
  60         }
  61         auto e = expr->getArg(0)->IgnoreParenImpCasts();
  62         while (auto const cast = dyn_cast<ExplicitCastExpr>(e))
  63         {
  64             if (!loplugin::TypeCheck(cast->getTypeAsWritten()).Pointer().Void())
  65             {
  66                 break;
  67             }
  68             e = cast->getSubExprAsWritten()->IgnoreParenImpCasts();
  69         }
  70         QualType t;
  71         if (auto const t1 = e->getType()->getAs<clang::PointerType>())
  72         {
  73             t = t1->getPointeeType();
  74         }
  75         else if (e->getType()->isArrayType())
  76         {
  77             t = e->getType();
  78             while (auto const t2 = t->getAsArrayTypeUnsafe())
  79             {
  80                 t = t2->getElementType();
  81             }
  82         }
  83         else
  84         {
  85             if (isDebugMode())
  86             {
  87                 report(DiagnosticsEngine::Fatal,
  88                        "unexpected call to %0 with first argument of non-pointer type %1",
  89                        expr->getExprLoc())
  90                     << fdecl << e->getType() << expr->getSourceRange();
  91                 report(DiagnosticsEngine::Note, "%0 declared here", fdecl->getLocation())
  92                     << fdecl << fdecl->getSourceRange();
  93             }
  94             return true;
  95         }
  96         auto const decl = t->getAsCXXRecordDecl();
  97         if (decl == nullptr)
  98         {
  99             return true;
 100         }
 101         if (!decl->isCompleteDefinition())
 102         {
 103             return true; // conservatively assume it may be trivial
 104         }
 105         if (decl->isTrivial())
 106         {
 107             return true;
 108         }
 109         report(DiagnosticsEngine::Warning,
 110                "%0 writing to an object of non-trivial type %1; use assignment instead",
 111                expr->getExprLoc())
 112             << fdecl << decl << expr->getSourceRange();
 113         return true;
 114     }
 115
 116     bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
 117
 118 private:
 119     void run() override
 120     {
 121         if (preRun())
 122         {
 123             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 124         }
 125     }
 126 };
 127
 128 loplugin::Plugin::Registration<ClassMemAccess> classmemaccess("classmemaccess");
 129 }
 130
 131 #endif
 132
 133 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */