[gcc r16-1973] libstdc++: construct bitset from string_view (P2697) [PR119742]
Nathan Myers
ncm@gcc.gnu.org
Thu Jul 3 11:47:30 GMT 2025
https://gcc.gnu.org/g:9930876ed788a7da18ccef0c91f4f12749da1df7
commit r16-1973-g9930876ed788a7da18ccef0c91f4f12749da1df7
Author: Nathan Myers <ncm@cantrip.org>
Date: Mon Jun 30 18:55:48 2025 -0400
libstdc++: construct bitset from string_view (P2697) [PR119742]
Add a bitset constructor from string_view, per P2697. Fix existing
tests that would fail to detect incorrect exception behavior.
Argument checks that result in exceptions guarded by "#if HOSTED"
are made unguarded because the functions called to throw just call
terminate() in free-standing builds. Improve readability in Doxygen
comments. Generalize a private member argument-checking function
to work with string and string_view without mentioning either,
obviating need for guards.
The version.h symbol is not "hosted" because string_view, though
not specified to be available in free-standing builds, is defined
there and the feature is useful there.
libstdc++-v3/ChangeLog:
PR libstdc++/119742
* include/bits/version.def: Add preprocessor symbol.
* include/bits/version.h: Add preprocessor symbol.
* include/std/bitset: Add constructor.
* testsuite/20_util/bitset/cons/1.cc: Fix.
* testsuite/20_util/bitset/cons/6282.cc: Fix.
* testsuite/20_util/bitset/cons/string_view.cc: Test new ctor.
* testsuite/20_util/bitset/cons/string_view_wide.cc: Test new ctor.
Diff:
---
libstdc++-v3/include/bits/version.def | 8 ++
libstdc++-v3/include/bits/version.h | 10 ++
libstdc++-v3/include/std/bitset | 82 ++++++++-----
libstdc++-v3/testsuite/20_util/bitset/cons/1.cc | 1 +
libstdc++-v3/testsuite/20_util/bitset/cons/6282.cc | 5 +-
.../testsuite/20_util/bitset/cons/string_view.cc | 132 +++++++++++++++++++++
.../20_util/bitset/cons/string_view_wide.cc | 8 ++
7 files changed, 215 insertions(+), 31 deletions(-)
diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index f4ba501c403f..b89b287e8e8f 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2030,6 +2030,14 @@ ftms = {
};
};
+ftms = {
+ name = bitset // ...construct from string_view
+ values = {
+ v = 202306;
+ cxxmin = 26;
+ };
+};
+
// Standard test specifications.
stds[97] = ">= 199711L";
stds[03] = ">= 199711L";
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index dc8ac07be166..a70a7ede68cf 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2273,4 +2273,14 @@
#endif /* !defined(__cpp_lib_exception_ptr_cast) && defined(__glibcxx_want_exception_ptr_cast) */
#undef __glibcxx_want_exception_ptr_cast
+#if !defined(__cpp_lib_bitset)
+# if (__cplusplus > 202302L)
+# define __glibcxx_bitset 202306L
+# if defined(__glibcxx_want_all) || defined(__glibcxx_want_bitset)
+# define __cpp_lib_bitset 202306L
+# endif
+# endif
+#endif /* !defined(__cpp_lib_bitset) && defined(__glibcxx_want_bitset) */
+#undef __glibcxx_bitset
+
#undef __glibcxx_want_all
diff --git a/libstdc++-v3/include/std/bitset b/libstdc++-v3/include/std/bitset
index 8b5d270c2a94..1c1e1670c33f 100644
--- a/libstdc++-v3/include/std/bitset
+++ b/libstdc++-v3/include/std/bitset
@@ -61,8 +61,13 @@
#endif
#define __glibcxx_want_constexpr_bitset
+#define __glibcxx_want_bitset // ...construct from string_view
#include <bits/version.h>
+#ifdef __cpp_lib_bitset // ...construct from string_view
+# include <string_view>
+#endif
+
#define _GLIBCXX_BITSET_BITS_PER_WORD (__CHAR_BIT__ * __SIZEOF_LONG__)
#define _GLIBCXX_BITSET_WORDS(__n) \
((__n) / _GLIBCXX_BITSET_BITS_PER_WORD + \
@@ -752,7 +757,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* (Note that %bitset does @e not meet the formal requirements of a
* <a href="tables.html#65">container</a>. Mainly, it lacks iterators.)
*
- * The template argument, @a Nb, may be any non-negative number,
+ * The template argument, `Nb`, may be any non-negative number,
* specifying the number of bits (e.g., "0", "12", "1024*1024").
*
* In the general unoptimized case, storage is allocated in word-sized
@@ -816,28 +821,25 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
typedef _Base_bitset<_GLIBCXX_BITSET_WORDS(_Nb)> _Base;
typedef unsigned long _WordT;
-#if _GLIBCXX_HOSTED
- template<class _CharT, class _Traits, class _Alloc>
- _GLIBCXX23_CONSTEXPR
- void
- _M_check_initial_position(const std::basic_string<_CharT, _Traits, _Alloc>& __s,
- size_t __position) const
+ template<class _Str>
+ _GLIBCXX23_CONSTEXPR void
+ _M_check_initial_position(
+ const _Str& __s, typename _Str::size_type __position) const
{
if (__position > __s.size())
- __throw_out_of_range_fmt(__N("bitset::bitset: __position "
- "(which is %zu) > __s.size() "
- "(which is %zu)"),
- __position, __s.size());
+ __throw_out_of_range_fmt(
+ __N("bitset::bitset:"
+ " __position (which is %zu) > __s.size() (which is %zu)"),
+ size_t(__position), size_t(__s.size()));
}
-#endif // HOSTED
_GLIBCXX23_CONSTEXPR
void _M_check(size_t __position, const char *__s) const
{
if (__position >= _Nb)
- __throw_out_of_range_fmt(__N("%s: __position (which is %zu) "
- ">= _Nb (which is %zu)"),
- __s, __position, _Nb);
+ __throw_out_of_range_fmt(
+ __N("%s: __position (which is %zu) >= _Nb (which is %zu)"),
+ __s, size_t(__position), size_t(_Nb));
}
_GLIBCXX23_CONSTEXPR
@@ -954,12 +956,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
#if _GLIBCXX_HOSTED
/**
* Use a subset of a string.
- * @param __s A string of @a 0 and @a 1 characters.
- * @param __position Index of the first character in @a __s to use;
+ * @param __s A string of `0` and `1` characters.
+ * @param __position Index of the first character in `__s` to use;
* defaults to zero.
- * @throw std::out_of_range If @a pos is bigger the size of @a __s.
+ * @throw std::out_of_range If `__position > __s.size()`.
* @throw std::invalid_argument If a character appears in the string
- * which is neither @a 0 nor @a 1.
+ * which is neither `0` nor `1`.
*/
template<class _CharT, class _Traits, class _Alloc>
_GLIBCXX23_CONSTEXPR
@@ -976,13 +978,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
/**
* Use a subset of a string.
- * @param __s A string of @a 0 and @a 1 characters.
- * @param __position Index of the first character in @a __s to use.
+ * @param __s A string of `0` and `1` characters.
+ * @param __position Index of the first character in `__s` to use.
* @param __n The number of characters to copy.
- * @throw std::out_of_range If @a __position is bigger the size
- * of @a __s.
+ * @throw std::out_of_range If `__position > __s.size()`.
* @throw std::invalid_argument If a character appears in the string
- * which is neither @a 0 nor @a 1.
+ * which is neither `0` nor `1`.
*/
template<class _CharT, class _Traits, class _Alloc>
_GLIBCXX23_CONSTEXPR
@@ -1008,15 +1009,42 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
}
#endif // HOSTED
+#ifdef __cpp_lib_bitset
+ /**
+ * Use a subset of a string view.
+ * @param __s A `string_view` of a sequence of `0` and `1` characters.
+ * @param __position Index of the first character in `__s` to use.
+ * @param __n The maximum number of characters from `__s` to use.
+ * @param __zero The character corresponding to the value 0.
+ * @param __one The character corresponding to the value 1.
+ * @throw std::out_of_range If `__position > __s.size()`.
+ * @throw std::invalid_argument If a character appears in `__s`
+ * which is neither `0` nor `1`.
+ */
+ template<class _CharT, class _Traits>
+ constexpr explicit
+ bitset(basic_string_view<_CharT, _Traits> __s,
+ basic_string_view<_CharT, _Traits>::size_type __position = 0,
+ basic_string_view<_CharT, _Traits>::size_type __n =
+ basic_string_view<_CharT, _Traits>::npos,
+ _CharT __zero = _CharT('0'), _CharT __one = _CharT('1'))
+ : _Base()
+ {
+ _M_check_initial_position(__s, __position);
+ _M_copy_from_ptr<_CharT, _Traits>(
+ __s.data(), __s.size(), __position, __n, __zero, __one);
+ }
+#endif
+
#if __cplusplus >= 201103L
/**
* Construct from a character %array.
- * @param __str An %array of characters @a zero and @a one.
+ * @param __str An %array of characters `__zero` and `__one`.
* @param __n The number of characters to use.
* @param __zero The character corresponding to the value 0.
* @param __one The character corresponding to the value 1.
* @throw std::invalid_argument If a character appears in the string
- * which is neither @a __zero nor @a __one.
+ * which is neither `__zero` nor `__one`.
*/
template<typename _CharT>
[[__gnu__::__nonnull__]]
@@ -1028,10 +1056,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_CharT __zero = _CharT('0'), _CharT __one = _CharT('1'))
: _Base()
{
-#if _GLIBCXX_HOSTED
if (!__str)
__throw_logic_error(__N("bitset::bitset(const _CharT*, ...)"));
-#endif
using _Traits = typename __bitset::__string<_CharT>::traits_type;
if (__n == __bitset::__string<_CharT>::npos)
diff --git a/libstdc++-v3/testsuite/20_util/bitset/cons/1.cc b/libstdc++-v3/testsuite/20_util/bitset/cons/1.cc
index 0a40b6cd9658..6441332c8d62 100644
--- a/libstdc++-v3/testsuite/20_util/bitset/cons/1.cc
+++ b/libstdc++-v3/testsuite/20_util/bitset/cons/1.cc
@@ -47,6 +47,7 @@ void test01(void)
const size_t n3 = 128;
try {
std::bitset<n3> bit03(str01, 5);
+ VERIFY(false);
}
catch(std::invalid_argument& fail) {
VERIFY( true );
diff --git a/libstdc++-v3/testsuite/20_util/bitset/cons/6282.cc b/libstdc++-v3/testsuite/20_util/bitset/cons/6282.cc
index fafa9fc808bc..ee348c35b2a3 100644
--- a/libstdc++-v3/testsuite/20_util/bitset/cons/6282.cc
+++ b/libstdc++-v3/testsuite/20_util/bitset/cons/6282.cc
@@ -39,6 +39,8 @@ void test02(void)
std::bitset<0> z3(std::string("10101010101"));
VERIFY( z3.any() == false );
+ VERIFY( z1.to_ulong() == 0 );
+ VERIFY( (z1.to_string<char,char_traits<char>,allocator<char> >().empty() ));
try {
z1.set(0);
VERIFY( false );
@@ -49,9 +51,6 @@ void test02(void)
catch(...) {
VERIFY( false );
}
-
- VERIFY( z1.to_ulong() == 0 );
- VERIFY( (z1.to_string<char,char_traits<char>,allocator<char> >().empty() ));
}
int main()
diff --git a/libstdc++-v3/testsuite/20_util/bitset/cons/string_view.cc b/libstdc++-v3/testsuite/20_util/bitset/cons/string_view.cc
new file mode 100644
index 000000000000..ec3a6c86b681
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/bitset/cons/string_view.cc
@@ -0,0 +1,132 @@
+// C++26 [bitset.cons]
+
+// { dg-do run { target c++26 } }
+
+#ifndef C
+# define C char
+# define L(s) s
+#endif
+
+#include <bitset>
+#include <string>
+#include <string_view>
+#include <algorithm> // std::reverse, std::transform
+#include <stdexcept>
+#include <testsuite_hooks.h>
+
+void test01()
+{
+ // template<_C,_T>
+ // constexpr explicit
+ // bitset(const basic_string_view<_C,_T>,
+ // size_type pos, size_type n, _C zero, _C one)
+ try {
+ std::basic_string_view<C> str(L("stuff smith sessions"));
+ const std::size_t n = 128;
+ std::bitset<n> bit(str, 5);
+ VERIFY(false);
+ }
+ catch(std::invalid_argument& fail) {
+ VERIFY( true );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+
+ try {
+ std::basic_string_view<C> str(L("010101000011"));
+ const std::size_t n = 128;
+ const auto sz = str.size();
+ std::bitset<n> bit(str, 0);
+ std::basic_string<C> str02;
+ for (std::size_t i = 0; i < sz; ++i)
+ str02 += (bit.test(i) ? C('1') : C('0'));
+ std::reverse(str02.begin(), str02.end());
+ VERIFY( str02 == str );
+ }
+ catch(std::invalid_argument& fail) {
+ VERIFY( false );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+
+ // substring<C> "010101000011"
+ // "10100001"
+ try {
+ std::basic_string_view<C> str(L("010101000011"));
+ const std::size_t n = 128;
+ const auto sz = 8;
+ std::bitset<n> bit(str, 3, sz);
+ std::basic_string<C> str02;
+ for (std::size_t i = 0; i < sz; ++i)
+ str02 += (bit.test(i) ? C('1') : C('0'));
+ std::reverse(str02.begin(), str02.end());
+ VERIFY( str02 == str.substr(3, sz) );
+ }
+ catch(std::invalid_argument& fail) {
+ VERIFY( false );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+
+ // "abababaaaabb", zero = 'a', one = 'b'
+ try {
+ std::basic_string_view<C> str(L("010101000011"));
+ const std::size_t n = 128;
+ const auto sz = str.size();
+ std::basic_string<C> str02(str);
+ std::transform(str02.cbegin(), str02.cend(), str02.begin(), [](auto c) {
+ return (c - C('0')) + C('a');
+ });
+ std::basic_string_view<C> str03(str02);
+ std::bitset<n> bit(str03, 0, 100, C('a'), C('b'));
+ std::basic_string<C> str04;
+ for (std::size_t i = 0; i < sz; ++i)
+ str04 += (bit.test(i) ? C('1') : C('0'));
+ std::reverse(str04.begin(), str04.end());
+ VERIFY( str04 == str );
+ }
+ catch(std::invalid_argument& fail) {
+ VERIFY( false );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+
+ // "aba0aba", zero = 'a', one = 'b', '0' appears
+ try {
+ const std::size_t n = 128;
+ std::basic_string_view<C> str05(L("aba0aba"));
+ std::bitset<n> bit(str05, 0, 100, C('a'), C('b'));
+ VERIFY( false );
+ }
+ catch(std::invalid_argument& fail) {
+ VERIFY( true );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+
+ // pos > str.size()
+ try {
+ std::basic_string_view<C> str(L("010101000011"));
+ const std::size_t n = 128;
+ const auto sz = str.size();
+ std::bitset<n> bit(str, sz + 1, 100);
+ VERIFY( false );
+ }
+ catch(std::out_of_range& fail) {
+ VERIFY( true );
+ }
+ catch(...) {
+ VERIFY( false );
+ }
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
diff --git a/libstdc++-v3/testsuite/20_util/bitset/cons/string_view_wide.cc b/libstdc++-v3/testsuite/20_util/bitset/cons/string_view_wide.cc
new file mode 100644
index 000000000000..b53fe74a7cef
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/bitset/cons/string_view_wide.cc
@@ -0,0 +1,8 @@
+// C++26 [bitset.cons]
+
+// { dg-do run { target c++26 } }
+
+#define C wchar_t
+#define L(s) L ## s
+
+#include "./string_view.cc"
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