From e35f91a70aedd6a2ce06311dea52f9c74e79ceba Mon Sep 17 00:00:00 2001 From: Beman Dawes Date: Tue, 22 May 2001 18:58:21 +0000 Subject: [PATCH] Smart pointer and utility changes related to adding checked_delere and checked_array_delete [SVN r10189] --- checked_delete_test.cpp | 31 +++++++++++++++++++++++++++ include/boost/utility.hpp | 45 ++++++++++++++++++++++++++++++++++----- utility.htm | 44 +++++++++++++++++++++++++++++++++++++- 3 files changed, 114 insertions(+), 6 deletions(-) create mode 100644 checked_delete_test.cpp diff --git a/checked_delete_test.cpp b/checked_delete_test.cpp new file mode 100644 index 0000000..f9107c8 --- /dev/null +++ b/checked_delete_test.cpp @@ -0,0 +1,31 @@ +// Boost checked_delete test program ---------------------------------------// + +// (C) Copyright Beman Dawes 2001. Permission to copy, use, modify, sell +// and distribute this software is granted provided this copyright +// notice appears in all copies. This software is provided "as is" without +// express or implied warranty, and with no claim as to its suitability for +// any purpose. + +// See http://www.boost.org for most recent version including documentation. + +// Revision History +// 21 May 01 Initial version (Beman Dawes) + +#include // for checked_delete + +// This program demonstrates compiler errors when trying to delete an +// incomplete type. + +namespace +{ + class Incomplete; +} + +int main() +{ + Incomplete * p; + boost::checked_delete(p); // should cause compile time error + Incomplete ** pa; + boost::checked_array_delete(pa); // should cause compile time error + return 0; +} // main diff --git a/include/boost/utility.hpp b/include/boost/utility.hpp index 82a7d13..5c2b766 100644 --- a/include/boost/utility.hpp +++ b/include/boost/utility.hpp @@ -11,6 +11,9 @@ // Classes appear in alphabetical order // Revision History +// 21 May 01 checked_delete() and checked_array_delete() added (Beman Dawes, +// suggested by Dave Abrahams, generalizing idea from Vladimir Prus) +// 21 May 01 made next() and prior() inline (Beman Dawes) // 26 Jan 00 protected noncopyable destructor added (Miki Jovanovic) // 10 Dec 99 next() and prior() templates added (Dave Abrahams) // 30 Aug 99 moved cast templates to cast.hpp (Beman Dawes) @@ -22,12 +25,44 @@ #ifndef BOOST_UTILITY_HPP #define BOOST_UTILITY_HPP -#include -#include // for size_t -#include // for std::pair +#include // broken compiler workarounds +#include // broken compiler workarounds +#include // for size_t +#include // for std::pair namespace boost { +// checked_delete() and checked_array_delete() -----------------------------// + + // verify that types are complete for increased safety + + template< typename T > +# if !defined(BOOST_MSVC) || BOOST_MSVC > 1200 + inline void checked_delete(T const volatile * x) +# else + inline void checked_delete(T /*const volatile*/ * x) +# endif + { +# if !defined(__BORLANDC__) || __BORLANDC__ > 0x0551 + BOOST_STATIC_ASSERT( sizeof(T) ); // assert type complete at point + // of instantiation +# endif + delete x; + } + + template< typename T > +# if !defined(BOOST_MSVC) || BOOST_MSVC > 1200 + inline void checked_array_delete(T const volatile * x) +# else + inline void checked_array_delete(T /*const volatile*/ * x) +# endif + { +# if !defined(__BORLANDC__) || __BORLANDC__ > 0x0551 + BOOST_STATIC_ASSERT( sizeof(T) ); // assert type complete at point + // of instantiation +# endif + delete [] x; + } // next() and prior() template functions -----------------------------------// @@ -41,10 +76,10 @@ namespace boost // Contributed by Dave Abrahams template - T next(T x) { return ++x; } + inline T next(T x) { return ++x; } template - T prior(T x) { return --x; } + inline T prior(T x) { return --x; } // class noncopyable -------------------------------------------------------// diff --git a/utility.htm b/utility.htm index 3fb8517..06efb65 100644 --- a/utility.htm +++ b/utility.htm @@ -16,10 +16,50 @@

Contents

+

Function templates checked_delete() and +checked_array_delete()

+ +

Deletion of a pointer to an incomplete type is an unsafe programming practice +because there is no way for the compiler to verify that the destructor is indeed +trivial.  The checked_delete() and checked_array_delete() function +templates simply delete or delete[] their argument, but also +require that their argument be a complete type.  They issue an appropriate +compiler error diagnostic if that requirement is not met.  A typical +implementation is shown; other implementations may vary:

+ +
    template< typename T >
+    inline void checked_delete(T const volatile * x)
+    {
+        BOOST_STATIC_ASSERT( sizeof(T) ); // assert type complete at point
+                                          // of instantiation
+        delete x;
+    }
+
+    template< typename T >
+    inline void checked_array_delete(T const volatile * x)
+    {
+        BOOST_STATIC_ASSERT( sizeof(T) ); // assert type complete at point
+                                          // of instantiation
+        delete [] x;
+    }
+ +

Contributed by Beman Dawes, based on a suggestion from Dave Abrahams, +generalizing an idea from Vladimir Prus, with comments from Rainer Deyke, John +Maddock, and others.

+ +

Background

+ +

The C++ Standard specifies that delete on a pointer to an incomplete types is +undefined behavior if the type has a non-trivial destructor in  [expr.delete] +5.3.5 paragraph.  No diagnostic is required.  Some but not all +compilers issue warnings if the type is incomplete at point of deletion.

+

Function templates next() and prior()

Certain data types, such as the C++ Standard Library's forward and @@ -91,9 +131,11 @@ emphasize that it is to be used only as a base class.  Dave Abrahams notes concern about the effect on compiler optimization of adding (even trivial inline) destructor declarations. He says "Probably this concern is misplaced, because noncopyable will be used mostly for classes which own resources and thus have non-trivial destruction semantics."

+

Function template tie()

+

See separate documentation.

Revised  08 March, 200122 May, 2001

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