Ideally this wouldn't be needed, because eventually these pointers all
get passed to either the basic_string_view(const CharT*) constructor, or
to basic_string_view::find(const CharT*), both of which already have the
attribute. But for that to work requires optimization, so that the null
value gets propagated through the call chain.
Adding it explicitly to each member that requires a non-null pointer
makes the diagnostics more reliable even without optimization. It's
better to give a diagnostic earlier anyway, at the actual problematic
call in the user's code.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (starts_with, ends_with, contains):
Add nonnull attribute.
* include/bits/cow_string.h (starts_with, ends_with, contains):
Likewise.
* include/std/string_view (starts_with, ends_with, contains):
Likewise.
* testsuite/21_strings/basic_string/operations/contains/nonnull.cc
* testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc
* testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc
* testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc
* testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc
* testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc
Until now operator+(char*, const string&) and operator+(const string&,
char*) had different performance characteristics. The former required a
single memory allocation and the latter required two. This patch makes
the performance equal.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (operator+(const string&, const char*)):
Remove naive implementation.
* include/bits/basic_string.tcc (operator+(const string&, const char*)):
Add single-allocation implementation.
Signed-off-by: Will Hawkins <whh8b@obs.cr>
I don't think this is required by the standard, but it's easy to
support.
libstdc++-v3/ChangeLog:
PR libstdc++/105995
* include/bits/basic_string.h (_M_use_local_data): Initialize
the entire SSO buffer.
* testsuite/21_strings/basic_string/cons/char/105995.cc: New test.
As confirmed by LWG 2852, the calls to traits_type::compare do not need
to be obsvervable, so we can make operator== compare string lengths
first and return immediately for non-equal lengths. This avoids doing a
slow string comparison for "abc...xyz" == "abc...xy". Previously we only
did this optimization for std::char_traits<char>, but we can enable it
unconditionally thanks to LWG 2852.
For comparisons with a const char* we can call traits_type::length right
away to do the same optimization. That strlen call can be folded away
for constant arguments, making it very efficient.
For the pre-C++20 operator== and operator!= overloads we can swap the
order of the arguments to take advantage of the operator== improvements.
libstdc++-v3/ChangeLog:
PR libstdc++/62187
* include/bits/basic_string.h (operator==): Always compare
lengths before checking string contents.
[!__cpp_lib_three_way_comparison] (operator==, operator!=):
Reorder arguments.
Defining the compare member functions inline allows calls to
traits_type::length and std::min to be inlined, taking advantage of
constant expression arguments. When not inline, the compiler prefers to
use the explicit instantiation definitions in libstdc++.so and can't
take advantage of constant arguments.
libstdc++-v3/ChangeLog:
PR libstdc++/59048
* include/bits/basic_string.h (compare): Define inline.
* include/bits/basic_string.tcc (compare): Remove out-of-line
definitions.
* include/bits/cow_string.h (compare): Define inline.
* testsuite/21_strings/basic_string/operations/compare/char/3.cc:
New test.
This new library issue was recently moved to Tentatively Ready by an LWG
poll, so I'm making the change on trunk.
As noted in PR libstc++/105907 the std::hash specializations for PMR
strings were not treated as slow hashes by the unordered containers, so
this change preserves that. The new specializations for custom
allocators are also not treated as slow, for the same reason. For the
versioned namespace (i.e. unstable ABI) we don't have to worry about
that, so can enable hash code caching for all basic_string
specializations.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__hash_str_base): New class
template.
(hash<basic_string<C, char_traits<C>, A>>): Define partial
specialization for each of the standard character types.
(hash<string>, hash<wstring>, hash<u8string>, hash<u16string>)
(hash<u32string>): Remove explicit specializations.
* include/std/string (__hash_string_base): Remove class
template.
(hash<pmr::string>, hash<pmr::wstring>, hash<pmr::u8string>)
(hash<pmr::u16string>, hash<pmr::u32string>): Remove explicit
specializations.
* testsuite/21_strings/basic_string/hash/hash.cc: Test with
custom allocators.
* testsuite/21_strings/basic_string/hash/hash_char8_t.cc:
Likewise.
Since the COW std::string was moved to its own header, we don't need the
atomic dispatch helpers in the definition of std::__cxx11::string. Move
the inclusion of the <ext/atomicity.h> header to <bits/cow_string.h>
where it's needed.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h: Do not include <ext/atomicity.h>
here.
* include/bits/cow_string.h: Include it here.
The new deleted constructors added by P2166R1 are a breaking change,
making previously valid code ill-formed in C++23. As a result, they
should only be defined for C++23 and not for C++11 and up.
libstdc++-v3/ChangeLog:
PR libstdc++/104099
* include/bits/basic_string.h (basic_string(nullptr_t)): Only
define for C++23.
(operator=(nullptr_t)): Likewise.
* include/bits/cow_string.h: Likewise.
* include/std/string_view (basic_string_view(nullptr_t)):
Likewise.
* testsuite/21_strings/basic_string/cons/char/nullptr.cc: Adjust
expected error. Add examples that become ill-formed in C++23.
* testsuite/21_strings/basic_string_view/cons/char/nonnull.cc:
Adjust expected errors.
* testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc:
Likewise.
The C++17 basic_string(const T&, size_t, size_t) constructor is
overconstrained, so it can't be used for a NTBS and a temporary string
gets constructed (potentially allocating memory). There is no
corresponding constructor taking an NTBS, so no need to disambiguate
from it. Accepting an NTBS avoids the temporary (and potential
allocation) and is what the standard requires.
libstdc++-v3/ChangeLog:
PR libstdc++/103919
* include/bits/basic_string.h (basic_string(const T&, size_t, size_t)):
Relax constraints on string_view parameter.
* include/bits/cow_string.h (basic_string(const T&, size_t, size_t)):
Likewise.
* testsuite/21_strings/basic_string/cons/char/103919.cc: New test.
In the testcase for 103534 we get a warning about append leading to memcpy
of a very large number of bytes overflowing the buffer. This turns out to
be because we weren't calling _M_check_length for string append. Rather
than do that directly, let's go through the public pointer append that calls
it.
PR c++/103534
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (append (basic_string)): Call pointer
append instead of _M_append directly.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wstringop-overflow-8.C: New test.
This adds std::__is_constant_evaluated() as a C++11 wrapper for
__builtin_is_constant_evaluated, but just returning false if the
built-in isn't supported by the compiler. This allows us to use it
throughout the library without checking __has_builtin every time.
Some uses in std::vector and std::string can only be constexpr when the
std::is_constant_evaluated() function actually works, so we might as
well guard them with a relevant macro and call that function directly,
rather than the built-in or std::__is_constant_evaluated().
The remaining checks of the __cpp_lib_is_constant_evaluated macro could
now be replaced by checking __cplusplus >= 202002 instead, but there's
no practical difference. We still need some kind of preprocessor check
there anyway.
libstdc++-v3/ChangeLog:
* doc/doxygen/user.cfg.in (PREDEFINED): Change macro name.
* include/bits/allocator.h (allocate, deallocate): Use
std::__is_constant_evaluated() unconditionally, instead of
checking whether std::is_constant_evaluated() (or the built-in)
can be used.
* include/bits/basic_string.h: Check new macro. call
std::is_constant_evaluated() directly in C++20-only code that is
guarded by a suitable macro.
* include/bits/basic_string.tcc: Likewise.
* include/bits/c++config (__is_constant_evaluated): Define.
(_GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED): Replace with ...
(_GLIBCXX_HAVE_IS_CONSTANT_EVALUATED): New macro.
* include/bits/char_traits.h (char_traits): Replace conditional
calls to std::is_constant_evaluated with unconditional calls to
std::__is_constant_evaluated.
* include/bits/cow_string.h: Use new macro.
* include/bits/ranges_algobase.h (__copy_or_move): Replace
conditional calls to std::is_constant_evaluated with unconditional
calls to std::__is_constant_evaluated.
(__copy_or_move_backward, __fill_n_fn): Likewise.
* include/bits/ranges_cmp.h (ranges::less): Likewise.
* include/bits/stl_algobase.h (lexicographical_compare_three_way):
Likewise.
* include/bits/stl_bvector.h: Call std::is_constant_evaluated
directly in C++20-only code that is guarded by a suitable macro.
* include/bits/stl_construct.h (_Construct, _Destroy, _Destroy_n):
Replace is_constant_evaluated with __is_constant_evaluated.
* include/bits/stl_function.h (greater, less, greater_equal)
(less_equal): Replace __builtin_is_constant_evaluated and
__builtin_constant_p with __is_constant_evaluated.
* include/bits/stl_vector.h: Call std::is_constant_evaluated()
in C++20-only code.
* include/debug/helper_functions.h (__check_singular): Use
__is_constant_evaluated instead of built-in, or remove check
entirely.
* include/std/array (operator<=>): Use __is_constant_evaluated
unconditionally.
* include/std/bit (__bit_ceil): Likewise.
* include/std/type_traits (is_constant_evaluated): Define using
'if consteval' if possible.
* include/std/version: Use new macro.
* libsupc++/compare: Use __is_constant_evaluated instead of
__builtin_is_constant_evaluated.
* testsuite/23_containers/array/tuple_interface/get_neg.cc:
Adjust dg-error lines.
Clang gives errors for constexpr std::string because the memory returned
by std::allocator<T>::allocate does not contain any objects yet, and
attempting to set them using char_traits::assign or char_traits::copy
fails with:
assignment to object outside its lifetime is not allowed in a constant expression
*__result = *__first;
^
This adds code to std::char_traits to use std::construct_at to begin
lifetimes when called during constant evaluation. To support
specializations of std::basic_string that don't use std::char_traits
there is now another layer of wrapper around the allocator_traits, so
that the lifetime of characters is begun as soon as the memory is
allocated. By doing it in the char traits and allocator traits, the rest
of basic_string can ignore the problem.
While modifying char_traits::copy and char_traits::assign to begin
lifetimes for the constexpr cases, I also replaced their uses of
std::copy and std::fill_n respectively. That means we don't need
<bits/stl_algobase.h> for char_traits.
libstdc++-v3/ChangeLog:
PR libstdc++/103295
* include/bits/basic_string.h (_Alloc_traits): Replace typedef
with struct for C++20 mode.
* include/bits/basic_string.tcc (_M_replace): Use _Alloc_traits
for allocation.
* include/bits/char_traits.h (__gnu_cxx::char_traits::assign):
Use std::_Construct during constant evaluation.
(__gnu_cxx::char_traits::assign(CharT*, const CharT*, size_t)):
Likewise. Replace std::fill_n with memset or manual loop.
(__gnu_cxx::char_traits::copy): Likewise, replacing std::copy
with memcpy.
* include/ext/vstring.h: Include <bits/stl_algobase.h> for
std::min.
* include/std/string_view: Likewise.
* testsuite/21_strings/basic_string/capacity/char/resize_and_overwrite.cc:
Add constexpr test.
Several std::basic_string constructors dispatch to one of the
two-argument overloads of _M_construct, which then dispatches again to
_M_construct_aux to detect whether the arguments are iterators or not.
That then dispatches to one of _M_construct(size_type, char_type) or
_M_construct(Iter, Iter, iterator_traits<Iter>::iterator_category{}).
For most of those constructors this is a waste of time, because we know
the arguments are already iterators. For basic_string(const CharT*) and
basic_string(initializer_list<C>) we know that we call _M_construct with
two pointers, and for basic_string(const basic_string&) we call it with
two const_iterators. Those constructors can call the three-argument
overload of _M_construct with the iterator category tag right away,
without the intermediate dispatching.
The case where this doesn't apply is basic_string(InputIter, InputIter),
but for C++11 and later this is constrained so we know it's an iterator
here as well. We can restrict the dispatching in this constructor to
only be done for C++98 and to call _M_construct_aux directly, which
allows us to remove the two-argument _M_construct(InputIter, InputIter)
overload entirely.
N.B. When calling the three-arg _M_construct with pointers or string
iterators, we pass forward_iterator_tag not random_access_iterator_tag.
This is because it makes no difference which overload gets called, and
simplifies overload resolution to not have to do a base-to-derived
check. If we ever add a new overload of M_construct for random access
iterators we would have to revisit this, but that seems unlikely.
This patch also moves the __is_null_pointer checks from the three-arg
_M_construct into the constructors where a null pointer argument is
actually possible. This avoids redundant checks where we know we have a
non-null pointer, or don't have a pointer at all.
Finally, this patch replaces some try-blocks with an RAII type, so that
memory is deallocated during unwinding. This avoids the overhead of
catching and rethrowing an exception.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (_M_construct_aux): Only define
for C++98. Remove constexpr.
(_M_construct_aux_2): Likewise.
(_M_construct(InputIter, InputIter)): Remove.
(basic_string(const basic_string&)): Call _M_construct with
iterator category argument.
(basic_string(const basic_string&, size_type, const Alloc&)):
Likewise.
(basic_string(const basic_string&, size_type, size_type)):
Likewise.
(basic_string(const charT*, size_type, const Alloc&)): Likewise.
Check for null pointer.
(basic_string(const charT*, const Alloc&)): Likewise.
(basic_string(initializer_list<charT>, const Alloc&)): Call
_M_construct with iterator category argument.
(basic_string(const basic_string&, const Alloc&)): Likewise.
(basic_string(basic_string&&, const Alloc&)): Likewise.
(basic_string(_InputIter, _InputIter, const Alloc&)): Likewise
for C++11 and later, call _M_construct_aux for C++98.
* include/bits/basic_string.tcc
(_M_construct(I, I, input_iterator_tag)): Replace try-block with
RAII type.
(_M_construct(I, I, forward_iterator_tag)): Likewise. Remove
__is_null_pointer check.
Clang diagnoses that the new constexpr std::string constructors are not
usable in constant expressions, because they start to write to members
of the union without setting an active member.
This adds a new helper function which returns the address of the local
buffer after making it the active member.
This doesn't fix all problems with Clang, because it still refuses to
write to memory returned by the allocator.
libstdc++-v3/ChangeLog:
PR libstdc++/103295
* include/bits/basic_string.h (_M_use_local_data()): New
member function to make local buffer the active member.
(assign(const basic_string&)): Use it.
* include/bits/basic_string.tcc (_M_construct, reserve()):
Likewise.
Some tests fail when run with -D_GLIBCXX_USE_CXX11_ABI or -stdgnu++20.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (operator<=>): Use constexpr
unconditionally.
* testsuite/21_strings/basic_string/modifiers/constexpr.cc:
Require cxx11-abit effective target.
* testsuite/21_strings/headers/string/synopsis.cc: Add
conditional constexpr to declarations, and adjust relational
operators for C++20.
This is only supported for the cxx11 ABI, not for COW strings.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string, operator""s): Add
constexpr for C++20.
(basic_string::basic_string(basic_string&&)): Only copy
initialized portion of the buffer.
(basic_string::basic_string(basic_string&&, const Alloc&)):
Likewise.
* include/bits/basic_string.tcc (basic_string): Add constexpr
for C++20.
(basic_string::swap(basic_string&)): Only copy initialized
portions of the buffers.
(basic_string::_M_replace): Add constexpr implementation that
doesn't depend on pointer comparisons.
* include/bits/cow_string.h: Adjust comment.
* include/ext/type_traits.h (__is_null_pointer): Add constexpr.
* include/std/string (erase, erase_if): Add constexpr.
* include/std/version (__cpp_lib_constexpr_string): Update
value.
* testsuite/21_strings/basic_string/cons/char/constexpr.cc:
New test.
* testsuite/21_strings/basic_string/cons/wchar_t/constexpr.cc:
New test.
* testsuite/21_strings/basic_string/literals/constexpr.cc:
New test.
* testsuite/21_strings/basic_string/modifiers/constexpr.cc: New test.
* testsuite/21_strings/basic_string/modifiers/swap/char/constexpr.cc:
New test.
* testsuite/21_strings/basic_string/modifiers/swap/wchar_t/constexpr.cc:
New test.
* testsuite/21_strings/basic_string/version.cc: New test.
A recently approved change for the C++23 working draft.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__cpp_lib_string_resize_and_overwrite):
Define for C++23.
(basic_string::resize_and_overwrite): Declare.
* include/bits/basic_string.tcc (basic_string::resize_and_overwrite):
Define.
* include/std/version (__cpp_lib_resize_and_overwrite): Define
for C++23.
* testsuite/21_strings/basic_string/capacity/char/resize_and_overwrite.cc:
New test.
The wstring and wstring_view typedefs should be enabled even if
<wchar.h> isn't supported, because char_traits<wchar_t> works
unconditionally. Similarly, the std::hash specializations for wide
strings do not depend on <wchar.h> support.
Although the primary template works OK for std::char_traits<wchar_t> in
the absence of <wchar.h> support, this patch still defines it as an
explicit specialization for compatibility with declarations that expect
it to be specialized. The explicit specialization just uses the same
__gnu_cxx::char_traits base class as the primary template.
libstdc++-v3/ChangeLog:
PR libstdc++/98725
* include/bits/char_traits.h (char_traits<wchar_t>): Define
explicit specialization unconditionally.
* include/bits/basic_string.h (hash<wstring>): Define
unconditionally. Do not check _GLIBCXX_USE_WCHAR_T.
* include/bits/stringfwd.h (wstring): Likewise.
* include/debug/string (wstring): Likewise.
* include/experimental/string_view (experimental::wstring_view)
(hash<experimental::wstring_view>): Likewise.
* include/std/string (pmr::wstring, hash<pmr::wstring>):
Likewise.
* include/std/string_view (wstring_view, hash<wstring_view>):
Likewise.
Implement this C++23 feature. Because construction from a null pointer
is undefined, we can implement it for C++11 and up, turning undefined
behaviour into a compilation error.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string(nullptr_t)): Define
as deleted.
(operator=(nullptr_t)): Likewise.
* include/bits/cow_string.h (basic_string(nullptr_t)): Likewise.
(operator=(nullptr_t)): Likewise.
* include/std/string_view (basic_string_view(nullptr_t)):
Likewise.
* testsuite/21_strings/basic_string/cons/char/nullptr.cc: New test.
* testsuite/21_strings/basic_string_view/cons/char/nonnull.cc:
Change dg-warning to dg-error.
* testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc:
Likewise.
When the values is guaranteed to fit in the SSO buffer we know the
string won't allocate, so the function can be noexcept. For 32-bit
integers, we know they need no more than 9 bytes (or 10 with a minus
sign) and the SSO buffer is 15 bytes.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
(to_string): Add noexcept if the type width is 32 bits or less.
This moves the definitions of the COW string to a separate file, so that
they don't need to be preprocessed for the common case. We could also
move the SSO string definitions to a new file, so that they don't need
to be preprocessed for the old ABI case, but that would require more
shovel work because there are some parts of <bits/basic_string.h> and
<bits/basic_string.tcc> that are common to both definitions.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/basic_string.h [!_GLIBCXX_USE_CXX11_ABI]
(basic_string): Move definition of Copy-on-Write string to
new file.
* include/bits/basic_string.tcc: Likewise.
* include/bits/cow_string.h: New file.
This removes the helper functions added by r8-1294 to detect whether the
char_traits member functions can be evaluated at compile time. Instead,
we can just use __builtin_constant_evaluated directly, which is well
supported by non-GCC compilers by now.
As a result, there is a chance that those members will no longer be
usable in constant expressions when using old versions of non-GCC
compilers. Make the relevant feature test macros depend on the
availability of __builtin_constant_evaluated, so they are defined only
when the feature is actualyl available.
The new testcase from the PR is added to the libitm testsuite, because
that's where we can be sure it's OK to use the -fgnu-tm option.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/91488
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__cpp_lib_constexpr_string): Only
define when is_constant_evaluated is available.
* include/bits/char_traits.h (__cpp_lib_constexpr_char_traits):
Likewise.
(__constant_string_p, __constant_array_p): Remove.
(char_traits): Use is_constant_evaluated directly.
* include/std/version (__cpp_lib_constexpr_char_traits)
(__cpp_lib_constexpr_string): Only define when
is_constant_evaluated is available.
libitm/ChangeLog:
* testsuite/libitm.c++/libstdc++-pr91488.C: New test.
This fixes a ubsan error when constructing a string with a null pointer:
bits/basic_string.h:534:21: runtime error: applying non-zero offset 18446744073709551615 to null pointer
The _M_construct function only cares whether the second pointer is
non-null, so create a non-null value without undefined arithmetic.
We can also pass the random_access_iterator_tag directly to the
_M_construct function, to avoid going via the tag dispatching
_M_construct_aux, because we know we have pointers not integers here.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string(const CharT*, const A&)):
Do not do arithmetic on null pointer.
The __cpp_lib_constexpr_string and __cpp_lib_semaphore feature test
macros are not defined consistently in <version> and the relevant header
for the feature.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__cpp_lib_constexpr_string):
Only define for C++17 and later.
* include/std/version (__cpp_lib_semaphore): Fix condition
to match the one in <semaphore>.
As noted in r11-1339-gb6ab9ecd550227684643b41e9e33a4d3466724d8 we define
a non-standard __cpp_lib_constexpr_char_traits feature test macro to
indicate support for P0426R1 and P1032R1. At some point last year the
__cpp_lib_constexpr_string macro was retconned to indicate support for
those papers. This adds the new macro (which we didn't previously
define, because it referred to P0980R1 "Making std::string constexpr"
which we don't support).
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__cpp_lib_constexpr_string): Define.
* include/std/version (__cpp_lib_constexpr_string): Define.
* testsuite/21_strings/char_traits/requirements/constexpr_functions_c++17.cc:
Check for __cpp_lib_constexpr_string.
* testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc:
Likewise.
* testsuite/21_strings/char_traits/requirements/version.cc: New test.
libstdc++-v3/ChangeLog:
* include/bits/alloc_traits.h: Use markdown for code font.
* include/bits/basic_string.h: Fix @param names.
* include/bits/max_size_type.h: Remove period after @file.
* include/bits/regex.h: Fix duplicate @retval names, and rename.
* include/ext/pb_ds/detail/priority_queue_base_dispatch.hpp: Add
group open to match existing group close.
* include/ext/pb_ds/priority_queue.hpp: Add blank line before group
open.
This implements WG21 P1679R3, adding contains member functions to
basic_string_view and basic_string.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string::contains): New
member functions.
* include/std/string_view (basic_string_view::contains):
Likewise.
* include/std/version (__cpp_lib_string_contains): Define.
* testsuite/21_strings/basic_string/operations/starts_with/char/1.cc:
Remove trailing whitespace.
* testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/operations/contains/char/1.cc: New test.
* testsuite/21_strings/basic_string/operations/contains/wchar_t/1.cc: New test.
* testsuite/21_strings/basic_string_view/operations/contains/char/1.cc: New test.
* testsuite/21_strings/basic_string_view/operations/contains/char/2.cc: New test.
* testsuite/21_strings/basic_string_view/operations/contains/wchar_t/1.cc: New test.
There are a lot of very simple constructors for the old string which are
not defined inline. I don't see any reason for this and it probably
makes them less likely to be optimized away. Move the definitions into
the class body.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string(const Alloc&))
(basic_string(const basic_string&)
(basic_string(const CharT*, size_type, const Alloc&))
(basic_string(const CharT*, const Alloc&))
(basic_string(size_type, CharT, const Alloc&))
(basic_string(initializer_list<CharT>, const Alloc&))
(basic_string(InputIterator, InputIterator, const Alloc&)):
Define inline in class body.
* include/bits/basic_string.tcc (basic_string(const Alloc&))
(basic_string(const basic_string&)
(basic_string(const CharT*, size_type, const Alloc&))
(basic_string(const CharT*, const Alloc&))
(basic_string(size_type, CharT, const Alloc&))
(basic_string(initializer_list<CharT>, const Alloc&))
(basic_string(InputIterator, InputIterator, const Alloc&)):
Move definitions into class body.
The basic_string deduction guides are defined for the old ABI, but the
tests are currently disabled. This is because a single case fails when
using the old ABI, which is just because LWG 3706 isn't implemented for
the old ABI. That can be done easily, and the tests can be enabled.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h [!_GLIBCXX_USE_CXX11_ABI]
(basic_string(const _CharT*, const _Alloc&)): Constrain to
require an allocator-like type to fix CTAD ambiguity (LWG 3706).
* testsuite/21_strings/basic_string/cons/char/deduction.cc:
Remove dg-skip-if.
* testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc:
Likewise.
The C++ LWG recently confirmed that self-move assignment should not have
undefined behaviour for standard containers (see the proposed resolution
of LWG 2839). The result should be a valid but unspecified value, just
like other times when a container is moved from.
Our std::list, std::__cxx11::basic_string and unordered containers all
have bugs which result in undefined behaviour.
For std::list the problem is that we clear the previous contents using
_M_clear() instead of clear(). This means the _M_next, _M_prev and
_M_size members are not zeroed, and so after we "update" them (with
their existing values), we are left with dangling pointers and a
non-zero size, but no elements.
For the unordered containers the problem is similar. _Hashtable first
deallocates the existing contents, then takes ownership of the pointers
from the RHS object (which has just had its contents deallocated so the
pointers are dangling).
For std::basic_string it's a little more subtle. When the string is
local (i.e. fits in the SSO buffer) we use char_traits::copy to copy the
contents from this->data() to __rhs.data(). When &__rhs == this that
copy violates the precondition that the ranges don't overlap. We only
need to check for self-move for this case where it's local, because the
only other case that can be true for self-move is that it's non-local
but the allocators compare equal. In that case the data pointer is
neither deallocated nor leaked, so the result is well-defined.
This patch also makes a small optimization for std::deque move
assignment, to use the efficient move when is_always_equal is false, but
the allocators compare equal at runtime.
Finally, we need to remove all the Debug Mode checks which abort the
program when a self-move is detected, because it's not undefined to do
that.
Before PR 85828 can be closed we should also look into fixing
std::shuffle so it doesn't do any redundant self-swaps.
libstdc++-v3/ChangeLog:
PR libstdc++/85828
* include/bits/basic_string.h (operator=(basic_string&&)): Check
for self-move before copying with char_traits::copy.
* include/bits/hashtable.h (operator=(_Hashtable&&)): Check for
self-move.
* include/bits/stl_deque.h (_M_move_assign1(deque&&, false_type)):
Check for equal allocators.
* include/bits/stl_list.h (_M_move_assign(list&&, true_type)):
Call clear() instead of _M_clear().
* include/debug/formatter.h (__msg_self_move_assign): Change
comment.
* include/debug/macros.h (__glibcxx_check_self_move_assign):
(_GLIBCXX_DEBUG_VERIFY): Remove.
* include/debug/safe_container.h (operator=(_Safe_container&&)):
Remove assertion check for safe move and make it well-defined.
* include/debug/safe_iterator.h (operator=(_Safe_iterator&&)):
Remove assertion check for self-move.
* include/debug/safe_local_iterator.h
(operator=(_Safe_local_iterator&&)): Likewise.
* testsuite/21_strings/basic_string/cons/char/self_move.cc: New test.
* testsuite/23_containers/deque/cons/self_move.cc: New test.
* testsuite/23_containers/forward_list/cons/self_move.cc: New test.
* testsuite/23_containers/list/cons/self_move.cc: New test.
* testsuite/23_containers/set/cons/self_move.cc: New test.
* testsuite/23_containers/unordered_set/cons/self_move.cc: New test.
* testsuite/23_containers/vector/cons/self_move.cc: New test.
Remove ability for reserve(n) to reduce a string's capacity. Add a new
reserve() overload that makes a shrink-to-fit request, and make
shrink_to_fit() use that.
libstdc++-v3/ChangeLog:
2020-07-30 Andrew Luo <andrewluotechnologies@outlook.com>
Jonathan Wakely <jwakely@redhat.com>
* config/abi/pre/gnu.ver (GLIBCXX_3.4): Use less greedy
patterns for basic_string members.
(GLIBCXX_3.4.29): Export new basic_string::reserve symbols.
* doc/xml/manual/status_cxx2020.xml: Update P0966 status.
* include/bits/basic_string.h (shrink_to_fit()): Call reserve().
(reserve(size_type)): Remove default argument.
(reserve()): Declare new overload.
[!_GLIBCXX_USE_CXX11_ABI] (shrink_to_fit, reserve): Likewise.
* include/bits/basic_string.tcc (reserve(size_type)): Remove
support for shrinking capacity.
(reserve()): Perform shrink-to-fit operation.
[!_GLIBCXX_USE_CXX11_ABI] (reserve): Likewise.
* testsuite/21_strings/basic_string/capacity/1.cc: Adjust to
reflect new behavior.
* testsuite/21_strings/basic_string/capacity/char/1.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/char/18654.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/char/2.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/2.cc:
Likewise.
When compiled as C++20 the COW std::string fails due to assuming that
the allocator always defines size_type and difference_type. That has
been incorrect since C++11, but we got away with it for specializations
using std::allocator until those members were removed in C++20.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (size_type, difference_type):
Use allocator_traits to obtain the allocator's size_type and
difference_type.
Some more C++20 changes from P1614R2, "The Mothership has Landed".
This adds three-way comparison support to std::char_traits,
std::basic_string, std::basic_string_view, and std::sub_match.
* include/bits/basic_string.h (basic_string): Define operator<=> and
remove redundant comparison operators for C++20.
* include/bits/char_traits.h (__gnu_cxx::char_traits, char_traits):
Add comparison_category members.
(__detail::__char_traits_cmp_cat): New helper to get comparison
category from char traits class.
* include/bits/regex.h (regex_traits::_RegexMask::operator!=): Do not
define for C++20.
(sub_match): Define operator<=> and remove redundant comparison
operators for C++20.
(match_results): Remove redundant operator!= for C++20.
* include/std/string_view (basic_string_view): Define operator<=> and
remove redundant comparison operators for C++20.
* testsuite/21_strings/basic_string/operators/char/cmp_c++20.cc: New
test.
* testsuite/21_strings/basic_string/operators/wchar_t/cmp_c++20.cc:
New test.
* testsuite/21_strings/basic_string_view/operations/copy/char/
constexpr.cc: Initialize variable.
* testsuite/21_strings/basic_string_view/operations/copy/wchar_t/
constexpr.cc: Likewise.
* testsuite/21_strings/basic_string_view/operators/char/2.cc: Add
dg-do directive and remove comments showing incorrect signatures.
* testsuite/21_strings/basic_string_view/operators/wchar_t/2.cc:
Likewise.
* testsuite/21_strings/basic_string_view/operators/char/cmp_c++20.cc:
New test.
* testsuite/21_strings/basic_string_view/operators/wchar_t/cmp_c++20.cc:
New test.
* testsuite/28_regex/sub_match/compare_c++20.cc: New test.
C++20 removes a number of std::allocator members that have correct
defaults provided by std::allocator_traits, so aren't needed.
Several extensions including __gnu_cxx::hash_map and tr1 containers are
no longer usable with std::allocator in C++20 mode. They need to be
updated to use __gnu_cxx::__alloc_traits in a follow-up patch.
* include/bits/alloc_traits.h
(allocator_traits<allocator<T>>::allocate): Ignore hint for C++20.
(allocator_traits<allocator<T>>::construct): Perform placement new
directly for C++20, instead of calling allocator<T>::construct.
(allocator_traits<allocator<T>>::destroy): Call destructor directly
for C++20, instead of calling allocator<T>::destroy.
(allocator_traits<allocator<T>>::max_size): Return value directly
for C++20, instead of calling std::allocator<T>::max_size().
(__do_alloc_on_copy, __do_alloc_on_move, __do_alloc_on_swap): Do not
define for C++17 and up.
(__alloc_on_copy, __alloc_on_move, __alloc_on_swap): Use if-constexpr
for C++17 and up, instead of tag dispatching.
* include/bits/allocator.h (allocator<void>): Remove for C++20.
(allocator::pointer, allocator::const_pointer, allocator::reference)
(allocator::const_reference, allocator::rebind): Remove for C++20.
* include/bits/basic_string.h (basic_string): Use __alloc_traits to
rebind allocator.
* include/bits/memoryfwd.h (allocator<void>): Remove for C++20.
* include/ext/debug_allocator.h: Use __alloc_traits for rebinding.
* include/ext/malloc_allocator.h (malloc_allocator::~malloc_allocator)
(malloc_allocator::pointer, malloc_allocator::const_pointer)
(malloc_allocator::reference, malloc_allocator::const_reference)
(malloc_allocator::rebind, malloc_allocator::max_size)
(malloc_allocator::construct, malloc_allocator::destroy): Do not
define for C++20.
(malloc_allocator::_M_max_size): Define new function.
* include/ext/new_allocator.h (new_allocator::~new_allocator)
(new_allocator::pointer, new_allocator::const_pointer)
(new_allocator::reference, new_allocator::const_reference)
(new_allocator::rebind, new_allocator::max_size)
(new_allocator::construct, new_allocator::destroy): Do not
define for C++20.
(new_allocator::_M_max_size): Define new function.
* include/ext/rc_string_base.h (__rc_string_base::_Rep): Use
__alloc_traits to rebind allocator.
* include/ext/rope (_Rope_rep_base, _Rope_base): Likewise.
(rope::rope(CharT, const allocator_type&)): Use __alloc_traits
to construct character.
* include/ext/slist (_Slist_base): Use __alloc_traits to rebind
allocator.
* include/ext/sso_string_base.h (__sso_string_base::_M_max_size):
Use __alloc_traits.
* include/ext/throw_allocator.h (throw_allocator): Do not use optional
members of std::allocator, use __alloc_traits members instead.
* include/ext/vstring.h (__versa_string): Use __alloc_traits.
* include/ext/vstring_util.h (__vstring_utility): Likewise.
* include/std/memory: Include <bits/alloc_traits.h>.
* testsuite/20_util/allocator/8230.cc: Use __gnu_test::max_size.
* testsuite/20_util/allocator/rebind_c++20.cc: New test.
* testsuite/20_util/allocator/requirements/typedefs.cc: Do not check
for pointer, const_pointer, reference, const_reference or rebind in
C++20.
* testsuite/20_util/allocator/requirements/typedefs_c++20.cc: New test.
* testsuite/23_containers/deque/capacity/29134.cc: Use
__gnu_test::max_size.
* testsuite/23_containers/forward_list/capacity/1.cc: Likewise.
* testsuite/23_containers/list/capacity/29134.cc: Likewise.
* testsuite/23_containers/map/capacity/29134.cc: Likewise.
* testsuite/23_containers/multimap/capacity/29134.cc: Likewise.
* testsuite/23_containers/multiset/capacity/29134.cc: Likewise.
* testsuite/23_containers/set/capacity/29134.cc: Likewise.
* testsuite/23_containers/vector/capacity/29134.cc: Likewise.
* testsuite/ext/malloc_allocator/variadic_construct.cc: Do not run
test for C++20.
* testsuite/ext/new_allocator/variadic_construct.cc: Likewise.
* testsuite/ext/vstring/capacity/29134.cc: Use __gnu_test::max_size.
* testsuite/util/replacement_memory_operators.h: Do not assume
Alloc::pointer exists.
* testsuite/util/testsuite_allocator.h (__gnu_test::max_size): Define
helper to call max_size for any allocator.
From-SVN: r277300
The std::to_chars functions from C++17 can be used to implement
std::to_string with much better performance than calling snprintf. Only
the __detail::__to_chars_len and __detail::__to_chars_10 functions are
needed for to_string, because it always outputs base 10 representations.
The return type of __detail::__to_chars_10 should not be declared before
C++17, so the function body is extracted into a new function that can be
reused by to_string and __detail::__to_chars_10.
The existing tests for to_chars rely on to_string to check for correct
answers. Now that they use the same code that doesn't actually ensure
correctness, so add new tests for std::to_string that compare against
printf output.
* include/Makefile.am: Add new <bits/charconv.h> header.
* include/Makefile.in: Regenerate.
* include/bits/basic_string.h (to_string(int), to_string(unsigned))
(to_string(long), to_string(unsigned long), to_string(long long))
(to_string(unsigned long long)): Rewrite to use __to_chars_10_impl.
* include/bits/charconv.h: New header.
(__detail::__to_chars_len): Move here from <charconv>.
(__detail::__to_chars_10_impl): New function extracted from
__detail::__to_chars_10.
* include/std/charconv (__cpp_lib_to_chars): Add, but comment out.
(__to_chars_unsigned_type): New class template that reuses
__make_unsigned_selector_base::__select to pick a type.
(__unsigned_least_t): Redefine as __to_chars_unsigned_type<T>::type.
(__detail::__to_chars_len): Move to new header.
(__detail::__to_chars_10): Add inline specifier. Move code doing the
output to __detail::__to_chars_10_impl and call that.
* include/std/version (__cpp_lib_to_chars): Add, but comment out.
* testsuite/21_strings/basic_string/numeric_conversions/char/
to_string.cc: Fix reference in comment. Remove unused variable.
* testsuite/21_strings/basic_string/numeric_conversions/char/
to_string_int.cc: New test.
From-SVN: r272186
2019-05-01 Nina Dinka Ranns <dinka.ranns@gmail.com>
Make allocator propagation more consistent for
operator+(basic_string) (P1165R1)
* include/bits/basic_string.h
(operator+(basic_string&&, basic_string&&): Changed resulting
allocator to always be the one from the first parameter.
* include/bits/basic_string.tcc
(operator+(const _CharT*, const basic_string&)): Changed
resulting allocator to be SOCCC on the second parameter's allocator.
(operator+(_CharT, const basic_string&)): Likewise.
* testsuite/21_strings/basic_string/allocator/char/operator_plus.cc:
New.
* testsuite/21_strings/basic_string/allocator/wchar_t/operator_plus.cc:
New.
From-SVN: r270953
The basic_string_view::pointer and basic_string_view::reference typedefs
are supposed to refer to the non-const value type.
In previous standards having traits_type::char_type different to
value_type was simply undefined, but in the C++2a draft it's ill-formed,
as changed by P1148R0. For std::basic_string and iostreams we might
want to only enforce this conditionally for __cplusplus > 201703L but
for std::basic_string_view we don't have backwards compatibility
concerns. Also add assertions to verify the _CharT argument is a
"char-like" type (non-array, trivial, standard layout type).
Also remove the non-standard basic_string_view::_M_check and
basic_string_view::_M_limit member functions, replacing them with
non-member functions that will still exist even if basic_string_view is
specialized by the program.
* include/experimental/string_view (basic_string_view::pointer)
(basic_string_view::reference): Fix to refer to non-const value_type.
* include/bits/basic_string.h (basic_string): Use __sv_check and
__sv_limit instead of basic_string_view::_M_check and
basic_string_view::_M_limit.
* include/std/string_view (__sv_check, __sv_limit): New
helper functions to replace basic_string_view::_M_check and
basic_string_view::_M_limit.
(basic_string_view): Add static assertions to enforce ill-formed
requirement for traits_type::char_type from P1148R0, and to enforce
required properties of char-like types.
(basic_string_view::pointer, basic_string_view::reference): Fix to
refer to non-const value_type.
(basic_string_view::operator[], basic_string_view::at)
(basic_string_view::front, basic_string_view::back)
(basic_string_view::data): Use const_reference and const_pointer
typedefs for return types.
(basic_string_view::_M_check, basic_string_view::_M_limit): Remove.
(hash<wstring_view>): Fix argument_type typedef.
* testsuite/21_strings/basic_string_view/modifiers/remove_prefix/
char/1.cc: Fix expected return type of basic_string_view::data().
* testsuite/21_strings/basic_string_view/modifiers/remove_prefix/
wchar_t/1.cc: Likewise.
* testsuite/21_strings/basic_string_view/modifiers/remove_suffix/
char/1.cc: Likewise.
* testsuite/21_strings/basic_string_view/modifiers/remove_suffix/
wchar_t/1.cc: Likewise.
* testsuite/21_strings/basic_string_view/requirements/traits_neg.cc:
New test.
* testsuite/21_strings/basic_string_view/requirements/typedefs.cc:
Check reference and pointer typedefs.
* testsuite/experimental/string_view/requirements/typedefs.cc:
Likewise.
* testsuite/experimental/string_view/modifiers/remove_prefix/char/1.cc:
Fix expected return type of basic_string_view::data().
* testsuite/experimental/string_view/modifiers/remove_prefix/wchar_t/
1.cc: Likewise.
* testsuite/experimental/string_view/modifiers/remove_suffix/char/1.cc:
Likewise.
* testsuite/experimental/string_view/modifiers/remove_suffix/wchar_t/
1.cc: Likewise.
From-SVN: r270548
A regression was introduced by the recent changes to provide the strong
exception safety guarantee for "never valueless" types that have O(1),
non-throwing move assignment. The problematic code is:
else if constexpr (__detail::__variant::_Never_valueless_alt<type>())
{
// This construction might throw:
variant __tmp(in_place_index<_Np>, __il,
std::forward<_Args>(__args)...);
// But _Never_valueless_alt<type> means this won't:
*this = std::move(__tmp);
}
When the variant is not assignable, the assignment is ill-formed, so
should not be attempted. When the variant has a copy assignment operator
but not a move assignment operator, the assignment performs a copy
assignment and that could throw, so should not be attempted.
The solution is to only take that branch when the variant has a move
assignment operator, which is determined by the _Traits::_S_move_assign
constant. When that is false the strong exception safety guarantee is
not possible, and so the __never_valueless function should also depend
on _S_move_assign.
While testing the fixes for this I noticed that the partial
specialization _Never_valueless_alt<basic_string<C,T,A>> incorrectly
assumed that is_nothrow_move_constructible<basic_string<C,T,A>> is
always true, but that's wrong for fully-dynamic COW strings. Fix the
partial specialization, and improve the comment describing
_Never_valueless_alt to be clear it depends on move construction as well
as move assignment.
Finally, I also observed that _Variant_storage<false, T...>::_M_valid()
was not taking advantage of the __never_valueless<T...>() function to
avoid a runtime check. Only the _Variant_storage<true, T...>::_M_valid()
function was using __never_valueless. That is also fixed.
PR libstdc++/87431
* include/bits/basic_string.h (_Never_valueless_alt): Make partial
specialization also depend on is_nothrow_move_constructible.
* include/std/variant (__detail::__variant::__never_valueless()):
Only true if the variant would have a move assignment operator.
(__detail::__variant::_Variant_storage<false, T...>::_M_valid()):
Check __never_valueless<T...>().
(variant::emplace): Only perform non-throwing move assignments
for never-valueless alternatives if the variant has a move assignment
operator.
* testsuite/20_util/variant/compile.cc: Check that never-valueless
types can be emplaced into non-assignable variants.
* testsuite/20_util/variant/run.cc: Check that never-valueless types
don't get copied when emplaced into non-assignable variants.
From-SVN: r270502
Avoid creating arbitrarily large objects on the stack when emplacing
trivially copyable objects into a variant. Currently we provide the
strong exception-safety guarantee for all trivially copyable types, by
constructing a second variant and then doing a non-throwing move
assignment from the temporary. This patch restricts that behaviour to
trivially copyable types that are no larger than 256 bytes. For larger
types the object will be emplaced directly into the variant, and if its
initialization throws then the variant becomes valueless.
Also implement Antony Polukhin's suggestion to whitelist specific types
that are not trivially copyable but can be efficiently move-assigned.
Emplacing those types will never cause a variant to become valueless.
The whitelisted types are: std::shared_ptr, std::weak_ptr,
std::unique_ptr, std::function, and std::any. Additionally,
std::basic_string, std::vector, and __gnu_debug::vector are whitelisted
if their allocator traits give them a non-throwing move assignment
operator. Specifically, this means std::string is whitelisted, but
std::pmr::string is not.
As part of this patch, additional if-constexpr branches are added for
the cases where the initialization is known to be non-throwing (so the
overhead of the try-catch block can be avoided) and where a scalar is
being produced by a potentially-throwing conversion operator (so that
the overhead of constructing and move-assigning a variant is avoided).
These changes should have no semantic effect, just better codegen.
PR libstdc++/87431 (again)
* include/bits/basic_string.h (__variant::_Never_valueless_alt):
Define partial specialization for basic_string.
* include/bits/shared_ptr.h (_Never_valueless_alt): Likewise for
shared_ptr and weak_ptr.
* include/bits/std_function.h (_Never_valueless_alt): Likewise for
function.
* include/bits/stl_vector.h (_Never_valueless_alt): Likewise for
vector.
* include/bits/unique_ptr.h (_Never_valueless_alt): Likewise for
unique_ptr.
* include/debug/vector (_Never_valueless_alt): Likewise for debug
vector.
* include/std/any (_Never_valueless_alt): Define explicit
specialization for any.
* include/std/variant (_Never_valueless_alt): Define primary template.
(__never_valueless): Use _Never_valueless_alt instead of
is_trivially_copyable.
(variant::emplace<N>(Args&&...)): Add special case for non-throwing
initializations to avoid try-catch overhead. Add special case for
scalars produced by potentially-throwing conversions. Use
_Never_valueless_alt instead of is_trivially_copyable for the
remaining strong exception-safety cases.
(variant::emplace<N>(initializer_list<U>, Args&&...)): Likewise.
* testsuite/20_util/variant/87431.cc: Run both test functions.
* testsuite/20_util/variant/exception_safety.cc: New test.
* testsuite/20_util/variant/run.cc: Use pmr::string instead of string,
so the variant becomes valueless.
From-SVN: r270170
Jonathan Wakely