Document: N2733=08-0243

Date: 2008-08-22

Authors: Benjamin Kosnik <bkoz@redhat.com>

Appendix C: ISO C++ 2003 Compatibility

General organization and editorial suggestions

This paper proposes a new section in Appendix C for compatibility between ISO C++ 2003 and ISO C++200x.

C.1 C++ and ISO C

and

C.2 Standard C library

into one grouping for both language and library features, such that

C.1 C++ and ISO C
C.1.1 Clause 2: lexical conventions

...

C.1.9 Clause 16: preprocessing directives [diff.cpp]

remain as-is, and then

C.1.10 Clause 18

C.1.11 Clause 20

C.1.11 Clause 21

are added, and the contents of

C.2.1

C.2.2

C.2.3

C.2.4

are moved into the appropriate place in C.1.*. Consider this an editorial suggestion.

Then, start with the C++2003 Compatibility with

C.2 C++ and ISO C++2003

And the rest of the text as is follows in this document.

If this arrangement is considered poor, then the existing layout can be used and C.3 C++ and ISO C++2003 can be used instead, and the text of this document can be added with the obvious transformation for whatever approved numbering scheme is in effect by the editor.

C.2.3 Clause 17 library introduction

17.4.1.3

Change: New includes.
Rationale: New functionality.
Effect on original feature: The following C++ include files are new: array, chrono, initializer_list, mutex, random, ratio, regex, sytem_error, and threads. In addition, the following C compatibility include files are new: ccomplex, cfenv, cinttypes, cstdbool, cstdint, ctgmath, and cuchar. Valid C++03 code that includes files with these names may be invalid in C++0x.

17.4.3.1.2

Change: New reserved namespace.
Rationale: New functionality.
Effect on original feature: The global namespace posix is now reserved for standardization. Valid C++03 code that used a top-level posix namespace may be invalid in C++0x.

C.2.4 Clause 18 library support

18.7

18.8

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x.

New identifiers, by include file:

<exception>

nested_exception, exception_ptr, current_exception, rethrow_exception, copy_exception, throw_with_nested, and rethrow_if_nested.

<initializer_list>

initializer_list

18.5.1.1
Change: Linking new/delete operators.

Rationale: Two throwing single-object signatures form base for other operators, clarifies that replacing these two changes others. Tighter requirements increase portability.

Effect on original feature: Valid C++03 code that replaces global new/delete operators may execute differently in C++0x.

For example:

    #include <cstdio>
    #include <cstdlib>
    #include <new>

    void* operator new(std::size_t size) throw(std::bad_alloc)
    {
        std::printf("custom allocation\n");
        if (size == 0)
            size = 1;
        void*p = std::malloc(size);
        if (p == 0)
            throw std::bad_alloc();
        return p;
    }

    void  operator delete(void* ptr) throw()
    {
      &nb!
 sp; std::printf("custom deallocation\n");
        std::free(ptr);
    }

    int main()
    {
        int* i = new int;
        delete i;
        int* a = new int[3];
        delete [] a;
    }

C.2.5 Clause 19 diagnostics

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

19.3

Change: Thread-local error numbers.
Rationale: Support new thread facilities.
Effect on original feature: Valid but implementation-defined C++-03 code that relies on errno being the same across threads may change behavior in C++-0x.

C.2.6 Clause 20 utilities

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

integral_constant, true_type, false_type, is_void, is_integral, is_floating_point, is_array, is_pointer, is_lvalue_reference, is_rvalue_reference, is_member_object_pointer, is_member_function_pointer, is_enum, is_union, is_class, is_function, is_reference, is_arithmetic, is_fundamental, is_member_pointer, is_scalar, is_object, is_compound, is_const, is_volatile, is_trivial, is_standard_layout, is_pod, is_empty, is_polymorphic, is_abstract, remove_const, remove_volatile, remove_cv, add_const, add_volatile, add_cv, remove_reference, add_reference, remove_pointer, add_pointer, is_signed, is_unsigned, rank, extent, remove_extent, remove_all_extents, has_trivial_default_contructor, has_trivial_copy_constructor, has_trivial_assign, has_trivial_destructor, has_nothrow_default_constructor, has_nothrow_copy_constructor, has_nothrow_assign, has_virtual_destructor, is_same, is_base_of, is_convertible,  aligned_storage, aligned_union, decay, enable_if, conditional, common_type

<utility>

C.2.7 Clause 21 strings

21.2

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

C.2.8 Clause 23 containers

23.2

23.4

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<array>

array, tuple_element, tuple_size, get

<forward_list>

forward_list

<unordered_map>

unordered_map, unordered_multimap

<unordered_set>

unordered_set, unordered_multiset

C.2.9 Clause 25 algorithms

25

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<algorithm>

all_of, any_of, none_of, find_if_not, copy_n, copy_if, partition_copy, partition_point

C.2.10 Clause 26 numerics

26.4.2

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<random>

C.2.11 Clause 27 io

Change: Change ios_base:: types that are bitmasks to be an enumeration with constexpr overloads.
Rationale: All bitmask types should be defined as enumerations with mask operators implemented as constexpr functions.
Effect on original feature: Define ios_base::fmtflags, ios_base::iostate, ios_base::openmode, ios_base::seekdir as enumerations.

Some code that depended on the implementation properties of these types being std::bitset or a builtin integer type may no longer compile.

For example:

    #include <iostream>

C.2.12 Clause 28 regex

28.4

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<regex>

C.2.13 Clause 29 atomics

29.0

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<cstdatomic>

C.2.14 Clause 30 threads

30.2

30.3

30.4

Change: New reserved identifiers.
Rationale: Required by new features.
Effect on original feature: Valid C++03 code that uses these identifiers may be invalid in C++0x. New identifiers, by include file:

<thread>

<mutex>

mutex, recursive_mutex, timed_mutex, recursive_timed_mutex, defer_lock_t, try_to_lock_t, adopt_lock_t, defer_lock, try_to_lock, adopt_lock, try_lock, lock, once_flag, call_once

<condition_variable>

condition_variable, condition_variable_any