From 8ec3116162e030709c42420fc70e7423db9a06df Mon Sep 17 00:00:00 2001 From: Stephan Bergmann Date: Tue, 8 Oct 2019 14:55:25 +0200 Subject: [PATCH] Introduce o3tl::unsafe_downcast for known-good dynamic_cast downcasts (This helps rewrite code that silences Coverity unchecked dynamic_cast warnings, like 57b89ea1c2ff07b53c3cc002e5ec9e52abd0c1bd "coverity#704563 Unchecked dynamic cast", in a way that is cleaner and potentially executes faster.) Change-Id: I3319c0eeec2aa822f686feacd499a76c8c9b9499 Reviewed-on: https://gerrit.libreoffice.org/80458 Tested-by: Jenkins Reviewed-by: Stephan Bergmann --- .../controller/main/DrawCommandDispatch.cxx | 8 ++--- include/o3tl/unsafe_downcast.hxx | 35 +++++++++++++++++++ o3tl/CompilerTest_o3tl_unsafe_downcast.mk | 16 +++++++++ o3tl/Module_o3tl.mk | 1 + o3tl/qa/compile-unsafe_downcast.cxx | 32 +++++++++++++++++ 5 files changed, 86 insertions(+), 6 deletions(-) create mode 100644 include/o3tl/unsafe_downcast.hxx create mode 100644 o3tl/CompilerTest_o3tl_unsafe_downcast.mk create mode 100644 o3tl/qa/compile-unsafe_downcast.cxx diff --git a/chart2/source/controller/main/DrawCommandDispatch.cxx b/chart2/source/controller/main/DrawCommandDispatch.cxx index 0c46970d926a..e8230b1d2eab 100644 --- a/chart2/source/controller/main/DrawCommandDispatch.cxx +++ b/chart2/source/controller/main/DrawCommandDispatch.cxx @@ -24,6 +24,7 @@ #include #include +#include #include #include #include @@ -161,12 +162,7 @@ void DrawCommandDispatch::setAttributes( SdrObject* pObj ) pObj->SetMergedItem( SdrTextHorzAdjustItem( SDRTEXTHORZADJUST_BLOCK ) ); pObj->SetMergedItem( makeSdrTextAutoGrowHeightItem( false ) ); - SdrObjCustomShape* pShape(dynamic_cast< SdrObjCustomShape* >( pObj )); - assert(pShape); - if(pShape) - { - pShape->MergeDefaultAttributes( &m_aCustomShapeType ); - } + o3tl::unsafe_downcast< SdrObjCustomShape* >( pObj )->MergeDefaultAttributes( &m_aCustomShapeType ); } } } diff --git a/include/o3tl/unsafe_downcast.hxx b/include/o3tl/unsafe_downcast.hxx new file mode 100644 index 000000000000..b49994eff135 --- /dev/null +++ b/include/o3tl/unsafe_downcast.hxx @@ -0,0 +1,35 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */ +/* + * 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/. + */ + +#ifndef INCLUDED_O3TL_UNSAFE_DOWNCAST_HXX +#define INCLUDED_O3TL_UNSAFE_DOWNCAST_HXX + +#include +#include + +namespace o3tl +{ +// Do a downcast from polymorphic `BasePtr` to `DerivedPtr` when it is known that `p` is actually +// pointing to an object of derived type (or is a nullptr). This is potentially cheaper than +// dynamic_cast and helps to avoid Coverity warnings about unchecked dynamic_cast. +template +std::enable_if_t< + (std::is_pointer_v< + DerivedPtr> && std::is_pointer_v && std::is_base_of_v, std::remove_pointer_t>), + DerivedPtr> +unsafe_downcast(BasePtr p) +{ + assert(p == nullptr || dynamic_cast(p) != nullptr); + return static_cast(p); +} +} + +#endif + +/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */ diff --git a/o3tl/CompilerTest_o3tl_unsafe_downcast.mk b/o3tl/CompilerTest_o3tl_unsafe_downcast.mk new file mode 100644 index 000000000000..0fbc8a247505 --- /dev/null +++ b/o3tl/CompilerTest_o3tl_unsafe_downcast.mk @@ -0,0 +1,16 @@ +# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t; fill-column: 100 -*- +# +# 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/. +# + +$(eval $(call gb_CompilerTest_CompilerTest,o3tl_unsafe_downcast)) + +$(eval $(call gb_CompilerTest_add_exception_objects,o3tl_unsafe_downcast, \ + o3tl/qa/compile-unsafe_downcast \ +)) + +# vim: set noet sw=4 ts=4: diff --git a/o3tl/Module_o3tl.mk b/o3tl/Module_o3tl.mk index 779b37ef56af..fa1516bca436 100644 --- a/o3tl/Module_o3tl.mk +++ b/o3tl/Module_o3tl.mk @@ -24,6 +24,7 @@ $(eval $(call gb_Module_add_targets,o3tl,\ $(eval $(call gb_Module_add_check_targets,o3tl,\ CppunitTest_o3tl_tests \ $(if $(COM_IS_CLANG),CompilerTest_o3tl_temporary) \ + $(if $(COM_IS_CLANG),CompilerTest_o3tl_unsafe_downcast) \ )) # vim: set noet sw=4: diff --git a/o3tl/qa/compile-unsafe_downcast.cxx b/o3tl/qa/compile-unsafe_downcast.cxx new file mode 100644 index 000000000000..8471fc250e88 --- /dev/null +++ b/o3tl/qa/compile-unsafe_downcast.cxx @@ -0,0 +1,32 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */ +/* + * 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 + +#include // expected-note@o3tl/unsafe_downcast.hxx:* 0+ {{}} + +struct Base +{ + virtual ~Base(); +}; + +struct Derived : Base +{ +}; + +void f(Base* b, Derived* d) +{ + o3tl::unsafe_downcast(b); + o3tl::unsafe_downcast(b); + o3tl::unsafe_downcast(*b); // expected-error {{}} + o3tl::unsafe_downcast(d); + o3tl::unsafe_downcast(d); // expected-error {{}} +} + +/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */