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Differential D70336

Explicitly enumerate std::string external instantiations.
AbandonedPublic

Authored by EricWF on Nov 15 2019, 12:47 PM.

Details

Reviewers
mclow.lists
ldionne
Summary

The external instantiation of std::string is a problem for libc++.

Additions and removals of inline functions in string can cause ABI
breakages, including introducing new symbols.

This patch aims to:
  (1) Make clear which functions are explicitly instatiated.
  (2) Prevent new functions from being accidentally instantiated.
  (3) Allow a migration path for adding or removing functions from the
  explicit instantiation over time.

Although this new formulation is uglier, it is preferable from a
maintainability and readability standpoint because it explicitly
enumerates the functions we've chosen to expose in our ABI. Changing
this list is non-trivial and requires thought and planning.

(3) is achieved by making it possible to control the extern template declaration
separately from it's definition. Meaning we could add a new definition to
the dylib, wait for it to roll out, then add the extern template
declaration to the header. Similarly, we could remove existing extern
template declarations while still keeping the definition to prevent ABI
breakages.

Diff Detail

Event Timeline

EricWF created this revision.Nov 15 2019, 12:47 PM
Herald added subscribers: libcxx-commits, dexonsmith, christof. · View Herald TranscriptNov 15 2019, 12:47 PM
ldionne accepted this revision.Nov 18 2019, 9:56 AM

I love this. It's more verbose but it also gives us more explicit control over our ABI list, which is great. We'll run into problems when wanting to explicitly instantiate the vtable of types that have one (if we eventually generalize this approach to other types). This is one of the reasons why I wrote http://wg21.link/p1263. However, none of this is needed for just std::string.

This revision is now accepted and ready to land.Nov 18 2019, 9:56 AM
EricWF updated this revision to Diff 237162.Jan 9 2020, 12:50 PM

Update and merge with master.

I'll be committing this shortly.

ldionne added a comment.Mar 11 2020, 12:18 PM

I think we went ahead with this approach in a different patch, didn't we? If so, can this be closed to clean up the review queue?

EricWF abandoned this revision.Mar 11 2020, 2:38 PM

Revision Contents

PathSize
libcxx/
include/
4 lines
54 lines
4 lines
src/
4 lines

Diff 237162

libcxx/include/__config

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#ifndef _LIBCPP_EXTERN_TEMPLATE #ifndef _LIBCPP_EXTERN_TEMPLATE
#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__; #define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
#endif #endif
#ifndef _LIBCPP_EXTERN_TEMPLATE2 #ifndef _LIBCPP_EXTERN_TEMPLATE2
#define _LIBCPP_EXTERN_TEMPLATE2(...) extern template __VA_ARGS__; #define _LIBCPP_EXTERN_TEMPLATE2(...) extern template __VA_ARGS__;
#endif #endif
#ifndef _LIBCPP_EXTERN_TEMPLATE_DEFINE
#define _LIBCPP_EXTERN_TEMPLATE_DEFINE(...) template __VA_ARGS__;
#endif
#if defined(__APPLE__) || defined(__FreeBSD__) || defined(_LIBCPP_MSVCRT_LIKE) || \ #if defined(__APPLE__) || defined(__FreeBSD__) || defined(_LIBCPP_MSVCRT_LIKE) || \
defined(__sun__) || defined(__NetBSD__) || defined(__CloudABI__) defined(__sun__) || defined(__NetBSD__) || defined(__CloudABI__)
#define _LIBCPP_LOCALE__L_EXTENSIONS 1 #define _LIBCPP_LOCALE__L_EXTENSIONS 1
#endif #endif
#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__)) #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
// Most unix variants have catopen. These are the specific ones that don't. // Most unix variants have catopen. These are the specific ones that don't.
# if !defined(__BIONIC__) && !defined(_NEWLIB_VERSION) # if !defined(__BIONIC__) && !defined(_NEWLIB_VERSION)
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libcxx/include/__string

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#endif #endif
_LIBCPP_PUSH_MACROS _LIBCPP_PUSH_MACROS
#include <__undef_macros> #include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_BEGIN_NAMESPACE_STD
// The the extern template ABI lists are kept outside of <string> to improve the
// readability of that header.
#define _LIBCPP_STRING_EXTERN_TEMPLATE_LIST(_Func, _CharType) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, std::allocator<_CharType> const&)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_not_of(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::~basic_string()) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_not_of(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(value_type)) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type)) \
_Func(_LIBCPP_FUNC_VIS const _CharType& basic_string<_CharType>::at(size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_of(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(value_type const*, size_type)) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::reserve(size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(basic_string const&, size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::copy(value_type*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, size_type, size_type, std::allocator<_CharType> const&)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_of(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by(size_type, size_type, size_type, size_type, size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by_and_replace(size_type, size_type, size_type, size_type, size_type, size_type, value_type const*)) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::push_back(value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::npos) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::erase(size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(basic_string const&, size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(value_type const*) const) \
_Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*) const) \
_Func(_LIBCPP_FUNC_VIS _CharType& basic_string<_CharType>::at(size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(value_type const*)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type const*, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, basic_string const&, size_type, size_type) const) \
_Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*, size_type) const) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(basic_string const&)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, basic_string const&, size_type, size_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::iterator basic_string<_CharType>::insert(basic_string::const_iterator, value_type)) \
_Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::resize(size_type, value_type)) \
_Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, basic_string const&, size_type, size_type))
// char_traits // char_traits
template <class _CharT> template <class _CharT>
struct _LIBCPP_TEMPLATE_VIS char_traits struct _LIBCPP_TEMPLATE_VIS char_traits
{ {
typedef _CharT char_type; typedef _CharT char_type;
typedef int int_type; typedef int int_type;
typedef streamoff off_type; typedef streamoff off_type;
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libcxx/include/string

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class _Allocator = allocator<_CharT>, class _Allocator = allocator<_CharT>,
class = typename enable_if<__is_allocator<_Allocator>::value, void>::type, class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
class _Sz = typename allocator_traits<_Allocator>::size_type class _Sz = typename allocator_traits<_Allocator>::size_type
> >
basic_string(basic_string_view<_CharT, _Traits>, _Sz, _Sz, const _Allocator& = _Allocator()) basic_string(basic_string_view<_CharT, _Traits>, _Sz, _Sz, const _Allocator& = _Allocator())
-> basic_string<_CharT, _Traits, _Allocator>; -> basic_string<_CharT, _Traits, _Allocator>;
#endif #endif
_LIBCPP_STRING_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, char)
_LIBCPP_STRING_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, wchar_t)
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
void void
basic_string<_CharT, _Traits, _Allocator>::__invalidate_all_iterators() basic_string<_CharT, _Traits, _Allocator>::__invalidate_all_iterators()
{ {
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__invalidate_all(this); __get_db()->__invalidate_all(this);
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basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
{ {
const value_type* __p = _VSTD::__to_address(__i->base()) + __n; const value_type* __p = _VSTD::__to_address(__i->base()) + __n;
return this->data() <= __p && __p < this->data() + this->size(); return this->data() <= __p && __p < this->data() + this->size();
} }
#endif // _LIBCPP_DEBUG_LEVEL >= 2 #endif // _LIBCPP_DEBUG_LEVEL >= 2
_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
#if _LIBCPP_STD_VER > 11 #if _LIBCPP_STD_VER > 11
// Literal suffixes for basic_string [basic.string.literals] // Literal suffixes for basic_string [basic.string.literals]
inline namespace literals inline namespace literals
{ {
inline namespace string_literals inline namespace string_literals
{ {
inline _LIBCPP_INLINE_VISIBILITY inline _LIBCPP_INLINE_VISIBILITY
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libcxx/src/string.cpp

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#include "stdexcept" #include "stdexcept"
#include <stdio.h> #include <stdio.h>
#include "__debug" #include "__debug"
_LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_BEGIN_NAMESPACE_STD
template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __basic_string_common<true>; template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __basic_string_common<true>;
template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_string<char>; _LIBCPP_STRING_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE_DEFINE, char)
template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_string<wchar_t>; _LIBCPP_STRING_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE_DEFINE, wchar_t)
template template
string string
operator+<char, char_traits<char>, allocator<char> >(char const*, string const&); operator+<char, char_traits<char>, allocator<char> >(char const*, string const&);
namespace namespace
{ {
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