In preparation for the deprecation of is_trivial (P3247R2), stop using it from std::string_view. Also, add the same detection to std::string (described in [strings.general]/2). libstdc++-v3/ChangeLog: * include/bits/basic_string.h: Add a static_assert on the char-like type. * include/std/string_view: Port away from is_trivial. Signed-off-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
In r15-3714-gd3a7302ec5985a I added -Wsystem-headers to the libstdc++ build flags to help catch problems in the library. This patch takes a different approach, of disabling the #pragma system_header unless _GLIBCXX_SYSHDR is defined. As a result, the testsuites will treat them as non-system-headers to get better warning coverage during regression testing of both gcc and libstdc++, not just when building the library. My rationale for the #ifdef instead of just removing the #pragma is the three G++ tests that want to test libstdc++ system header behavior, so we need a way to select it. This doesn't affect installed libraries, as they get their system-header status from the lookup path. But testsuite_flags --build-includes gives -I directives rather than -isystem. This patch doesn't change the headers in config/ because I'm not compiling with most of them, so won't see any warnings that need fixing. Adjusting them could happen later, or we can not bother. libstdc++-v3/ChangeLog: * acinclude.m4 (WARN_FLAGS): Remove -Wsystem-headers. * configure: Regenerate. * include/bits/algorithmfwd.h: #ifdef out #pragma GCC system_header. * include/bits/atomic_base.h * include/bits/atomic_futex.h * include/bits/atomic_timed_wait.h * include/bits/atomic_wait.h * include/bits/basic_ios.h * include/bits/basic_string.h * include/bits/boost_concept_check.h * include/bits/char_traits.h * include/bits/charconv.h * include/bits/chrono.h * include/bits/chrono_io.h * include/bits/codecvt.h * include/bits/concept_check.h * include/bits/cpp_type_traits.h * include/bits/elements_of.h * include/bits/enable_special_members.h * include/bits/erase_if.h * include/bits/forward_list.h * include/bits/functional_hash.h * include/bits/gslice.h * include/bits/gslice_array.h * include/bits/hashtable.h * include/bits/indirect_array.h * include/bits/invoke.h * include/bits/ios_base.h * include/bits/iterator_concepts.h * include/bits/locale_classes.h * include/bits/locale_facets.h * include/bits/locale_facets_nonio.h * include/bits/localefwd.h * include/bits/mask_array.h * include/bits/max_size_type.h * include/bits/memory_resource.h * include/bits/memoryfwd.h * include/bits/move_only_function.h * include/bits/node_handle.h * include/bits/ostream_insert.h * include/bits/out_ptr.h * include/bits/parse_numbers.h * include/bits/postypes.h * include/bits/quoted_string.h * include/bits/range_access.h * include/bits/ranges_base.h * include/bits/refwrap.h * include/bits/sat_arith.h * include/bits/semaphore_base.h * include/bits/slice_array.h * include/bits/std_abs.h * include/bits/std_function.h * include/bits/std_mutex.h * include/bits/std_thread.h * include/bits/stl_iterator_base_funcs.h * include/bits/stl_iterator_base_types.h * include/bits/stl_tree.h * include/bits/stream_iterator.h * include/bits/streambuf_iterator.h * include/bits/stringfwd.h * include/bits/this_thread_sleep.h * include/bits/unique_lock.h * include/bits/uses_allocator_args.h * include/bits/utility.h * include/bits/valarray_after.h * include/bits/valarray_array.h * include/bits/valarray_before.h * include/bits/version.h * include/c_compatibility/fenv.h * include/c_compatibility/inttypes.h * include/c_compatibility/stdint.h * include/decimal/decimal.h * include/experimental/bits/net.h * include/experimental/bits/shared_ptr.h * include/ext/aligned_buffer.h * include/ext/alloc_traits.h * include/ext/atomicity.h * include/ext/concurrence.h * include/ext/numeric_traits.h * include/ext/pod_char_traits.h * include/ext/pointer.h * include/ext/stdio_filebuf.h * include/ext/stdio_sync_filebuf.h * include/ext/string_conversions.h * include/ext/type_traits.h * include/ext/vstring.h * include/ext/vstring_fwd.h * include/ext/vstring_util.h * include/parallel/algorithmfwd.h * include/parallel/numericfwd.h * include/tr1/functional_hash.h * include/tr1/hashtable.h * include/tr1/random.h * libsupc++/exception.h * libsupc++/hash_bytes.h * include/bits/basic_ios.tcc * include/bits/basic_string.tcc * include/bits/fstream.tcc * include/bits/istream.tcc * include/bits/locale_classes.tcc * include/bits/locale_facets.tcc * include/bits/locale_facets_nonio.tcc * include/bits/ostream.tcc * include/bits/sstream.tcc * include/bits/streambuf.tcc * include/bits/string_view.tcc * include/bits/version.tpl * include/experimental/bits/string_view.tcc * include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp * include/ext/random.tcc * include/ext/vstring.tcc * include/tr2/bool_set.tcc * include/tr2/dynamic_bitset.tcc * include/bits/c++config * include/c/cassert * include/c/cctype * include/c/cerrno * include/c/cfloat * include/c/ciso646 * include/c/climits * include/c/clocale * include/c/cmath * include/c/csetjmp * include/c/csignal * include/c/cstdarg * include/c/cstddef * include/c/cstdio * include/c/cstdlib * include/c/cstring * include/c/ctime * include/c/cuchar * include/c/cwchar * include/c/cwctype * include/c_global/cassert * include/c_global/ccomplex * include/c_global/cctype * include/c_global/cerrno * include/c_global/cfenv * include/c_global/cfloat * include/c_global/cinttypes * include/c_global/ciso646 * include/c_global/climits * include/c_global/clocale * include/c_global/cmath * include/c_global/csetjmp * include/c_global/csignal * include/c_global/cstdalign * include/c_global/cstdarg * include/c_global/cstdbool * include/c_global/cstddef * include/c_global/cstdint * include/c_global/cstdio * include/c_global/cstdlib * include/c_global/cstring * include/c_global/ctgmath * include/c_global/ctime * include/c_global/cuchar * include/c_global/cwchar * include/c_global/cwctype * include/c_std/cassert * include/c_std/cctype * include/c_std/cerrno * include/c_std/cfloat * include/c_std/ciso646 * include/c_std/climits * include/c_std/clocale * include/c_std/cmath * include/c_std/csetjmp * include/c_std/csignal * include/c_std/cstdarg * include/c_std/cstddef * include/c_std/cstdio * include/c_std/cstdlib * include/c_std/cstring * include/c_std/ctime * include/c_std/cuchar * include/c_std/cwchar * include/c_std/cwctype * include/debug/array * include/debug/bitset * include/debug/deque * include/debug/forward_list * include/debug/list * include/debug/map * include/debug/set * include/debug/string * include/debug/unordered_map * include/debug/unordered_set * include/debug/vector * include/decimal/decimal * include/experimental/algorithm * include/experimental/any * include/experimental/array * include/experimental/buffer * include/experimental/chrono * include/experimental/contract * include/experimental/deque * include/experimental/executor * include/experimental/filesystem * include/experimental/forward_list * include/experimental/functional * include/experimental/internet * include/experimental/io_context * include/experimental/iterator * include/experimental/list * include/experimental/map * include/experimental/memory * include/experimental/memory_resource * include/experimental/net * include/experimental/netfwd * include/experimental/numeric * include/experimental/propagate_const * include/experimental/ratio * include/experimental/regex * include/experimental/scope * include/experimental/set * include/experimental/socket * include/experimental/string * include/experimental/string_view * include/experimental/synchronized_value * include/experimental/system_error * include/experimental/timer * include/experimental/tuple * include/experimental/type_traits * include/experimental/unordered_map * include/experimental/unordered_set * include/experimental/vector * include/ext/algorithm * include/ext/cmath * include/ext/functional * include/ext/iterator * include/ext/memory * include/ext/numeric * include/ext/random * include/ext/rb_tree * include/ext/rope * include/parallel/algorithm * include/std/algorithm * include/std/any * include/std/array * include/std/atomic * include/std/barrier * include/std/bit * include/std/bitset * include/std/charconv * include/std/chrono * include/std/codecvt * include/std/complex * include/std/concepts * include/std/condition_variable * include/std/coroutine * include/std/deque * include/std/execution * include/std/expected * include/std/filesystem * include/std/format * include/std/forward_list * include/std/fstream * include/std/functional * include/std/future * include/std/generator * include/std/iomanip * include/std/ios * include/std/iosfwd * include/std/iostream * include/std/istream * include/std/iterator * include/std/latch * include/std/limits * include/std/list * include/std/locale * include/std/map * include/std/memory * include/std/memory_resource * include/std/mutex * include/std/numbers * include/std/numeric * include/std/optional * include/std/ostream * include/std/print * include/std/queue * include/std/random * include/std/ranges * include/std/ratio * include/std/regex * include/std/scoped_allocator * include/std/semaphore * include/std/set * include/std/shared_mutex * include/std/span * include/std/spanstream * include/std/sstream * include/std/stack * include/std/stacktrace * include/std/stdexcept * include/std/streambuf * include/std/string * include/std/string_view * include/std/syncstream * include/std/system_error * include/std/text_encoding * include/std/thread * include/std/tuple * include/std/type_traits * include/std/typeindex * include/std/unordered_map * include/std/unordered_set * include/std/utility * include/std/valarray * include/std/variant * include/std/vector * include/std/version * include/tr1/array * include/tr1/cfenv * include/tr1/cinttypes * include/tr1/cmath * include/tr1/complex * include/tr1/cstdbool * include/tr1/cstdint * include/tr1/cstdio * include/tr1/cstdlib * include/tr1/cwchar * include/tr1/cwctype * include/tr1/functional * include/tr1/memory * include/tr1/random * include/tr1/regex * include/tr1/tuple * include/tr1/type_traits * include/tr1/unordered_map * include/tr1/unordered_set * include/tr1/utility * include/tr2/bool_set * include/tr2/dynamic_bitset * include/tr2/type_traits * libsupc++/atomic_lockfree_defines.h * libsupc++/compare * libsupc++/cxxabi.h * libsupc++/cxxabi_forced.h * libsupc++/cxxabi_init_exception.h * libsupc++/exception * libsupc++/initializer_list * libsupc++/new * libsupc++/typeinfo: Likewise. * testsuite/20_util/ratio/operations/ops_overflow_neg.cc * testsuite/23_containers/array/tuple_interface/get_neg.cc * testsuite/23_containers/vector/cons/destructible_debug_neg.cc * testsuite/24_iterators/operations/prev_neg.cc * testsuite/ext/type_traits/add_unsigned_floating_neg.cc * testsuite/ext/type_traits/add_unsigned_integer_neg.cc * testsuite/ext/type_traits/remove_unsigned_floating_neg.cc * testsuite/ext/type_traits/remove_unsigned_integer_neg.cc: Adjust line numbers. gcc/testsuite/ChangeLog * g++.dg/analyzer/fanalyzer-show-events-in-system-headers-default.C * g++.dg/analyzer/fanalyzer-show-events-in-system-headers-no.C * g++.dg/diagnostic/disable.C: #define _GLIBCXX_SYSHDR.
We get smaller code at all optimization levels by not creating a temporary object, just comparing lengths first and then using traits_type::compare. This does less work than calling substr then operator==. libstdc++-v3/ChangeLog: * include/std/string_view (starts_with(basic_string_view)): Compare lengths first and then call traits_type::compare directly.
The difference between __type_identity_t and std::type_identity_t is observable, as demonstrated in the PR. Nobody in LWG seems to think this an example we should really care about, but it seems easy and harmless to change this. libstdc++-v3/ChangeLog: PR libstdc++/114400 * include/std/string_view (operator==): Use std::type_identity_t in C++20 instead of our own __type_identity_t.
This was changed by LWG 3857. libstdc++-v3/ChangeLog: * include/std/string_view (basic_string_view(R&&)): Remove constraint that traits_type must be the same, as per LWG 3857. * testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc: Explicit conversion between different specializations should be allowed. * testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc: Likewise.
This C++26 change makes several classes "partially freestanding", but we already fully supported them in freestanding mode. All we need to do is define the new feature test macros and add tests for them. libstdc++-v3/ChangeLog: * include/bits/version.def (freestanding_algorithm) (freestanding_array, freestanding_optional) (freestanding_string_view, freestanding_variant): Add. * include/bits/version.h: Regenerate. * include/std/algorithm (__glibcxx_want_freestanding_algorithm): Define. * include/std/array (__glibcxx_want_freestanding_array): Define. * include/std/optional (__glibcxx_want_freestanding_optional): Define. * include/std/string_view (__glibcxx_want_freestanding_string_view): Define. * include/std/variant (__glibcxx_want_freestanding_variant): Define. * testsuite/20_util/optional/version.cc: Add checks for __cpp_lib_freestanding_optional. * testsuite/20_util/variant/version.cc: Add checks for __cpp_lib_freestanding_variant. * testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust dg-error line numbers. * testsuite/21_strings/basic_string_view/requirements/version.cc: New test. * testsuite/23_containers/array/requirements/version.cc: New test. * testsuite/25_algorithms/fill_n/requirements/version.cc: New test. * testsuite/25_algorithms/swap_ranges/requirements/version.cc: New test.
This change moves the definitions of feature test macros (or strictly speaking, the requests for <bits/version.h> to define them) so that only standard headers define them. For example, <bits/shared_ptr.h> will no longer define macros related to std::shared_ptr, only <memory> and <version> will define them. This means that __cpp_lib_shared_ptr_arrays will not be defined by <future> or by other headers that include <bits/shared_ptr.h>. It will only be defined when <memory> has been included. This will discourage users from relying on transitive includes. As a result, internal headers that need to query the macros should use the internal macros like __glibcxx_shared_ptr_arrays instead of __cpp_lib_shared_ptr_arrays, as those internal macros are defined by the internal headers after icluding <bits/version.h>. There are some exceptions to this rule, because __cpp_lib_is_constant_evaluated is defined by bits/c++config.h and so is available everywhere, and __cpp_lib_three_way_comparison is defined by <compare> which several headers are explicitly specified to include, so its macro is guaranteed to be usable too. N.B. not many internal headers actually need an explicit include of <bits/version.h>, because most of them include <type_traits> and so get all the __glibcxx_foo internal macros from there. libstdc++-v3/ChangeLog: * include/bits/algorithmfwd.h: Do not define standard feature test macro here. * include/bits/align.h: Likewise. Test internal macros instead of standard macros. * include/bits/alloc_traits.h: Likewise. * include/bits/allocator.h: Likewise. * include/bits/atomic_base.h: Likewise. * include/bits/atomic_timed_wait.h: Likewise. * include/bits/atomic_wait.h: Likewise. * include/bits/basic_string.h: Likewise. * include/bits/basic_string.tcc: Likewise. * include/bits/char_traits.h: Likewise. * include/bits/chrono.h: Likewise. * include/bits/cow_string.h: Likewise. * include/bits/forward_list.h: Likewise. * include/bits/hashtable.h: Likewise. * include/bits/ios_base.h: Likewise. * include/bits/memory_resource.h: Likewise. * include/bits/move.h: Likewise. * include/bits/move_only_function.h: Likewise. * include/bits/node_handle.h: Likewise. * include/bits/ptr_traits.h: Likewise. * include/bits/range_access.h: Likewise. * include/bits/ranges_algo.h: Likewise. * include/bits/ranges_cmp.h: Likewise. * include/bits/ranges_util.h: Likewise. * include/bits/semaphore_base.h: Likewise. * include/bits/shared_ptr.h: Likewise. * include/bits/shared_ptr_atomic.h: Likewise. * include/bits/shared_ptr_base.h: Likewise. * include/bits/stl_algo.h: Likewise. * include/bits/stl_algobase.h: Likewise. * include/bits/stl_function.h: Likewise. * include/bits/stl_iterator.h: Likewise. * include/bits/stl_list.h: Likewise. * include/bits/stl_map.h: Likewise. * include/bits/stl_pair.h: Likewise. * include/bits/stl_queue.h: Likewise. * include/bits/stl_stack.h: Likewise. * include/bits/stl_tree.h: Likewise. * include/bits/stl_uninitialized.h: Likewise. * include/bits/stl_vector.h: Likewise. * include/bits/unique_ptr.h: Likewise. * include/bits/unordered_map.h: Likewise. * include/bits/uses_allocator_args.h: Likewise. * include/bits/utility.h: Likewise. * include/bits/erase_if.h: Add comment. * include/std/algorithm: Define standard feature test macros here. * include/std/atomic: Likewise. * include/std/array: Likewise. * include/std/chrono: Likewise. * include/std/condition_variable: Likewise. * include/std/deque: Likewise. * include/std/format: Likewise. * include/std/functional: Likewise. * include/std/forward_list: Likewise. * include/std/ios: Likewise. * include/std/iterator: Likewise. * include/std/list: Likewise. * include/std/map: Likewise. * include/std/memory: Likewise. * include/std/numeric: Likewise. * include/std/queue: Likewise. * include/std/ranges: Likewise. * include/std/regex: Likewise. * include/std/set: Likewise. * include/std/stack: Likewise. * include/std/stop_token: Likewise. * include/std/string: Likewise. * include/std/string_view: * include/std/tuple: Likewise. * include/std/unordered_map: * include/std/unordered_set: * include/std/utility: Likewise. * include/std/vector: Likewise. * include/std/scoped_allocator: Query internal macros instead of standard macros.
LWG 3950 points out that the comparisons of std::basic_string_view can be simplified to just a single overload of operator== and a single overload of operator<=>. Those overloads work fine for homogeneous comparisons of two string view objects. libstdc++-v3/ChangeLog: * include/std/string_view (operator==, operator<=>): Remove redundant overloads (LWG 3950).