Re: [PATCH v2] libstdc++: C++23, implement WG21 P1679R3

[Jonathan Wakely <jwakely@redhat.com>]

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On 15/01/21 01:23 +0000, Paul Fee via Libstdc++ wrote:
>Add contains member function to basic_string_view and basic_string.
>
>The new method is enabled for -std=gnu++20, gnu++2b and c++2b.  This allows
>users to access the method as a GNU extension to C++20.  The conditional
>test may be reduced to "__cplusplus > 202011L" once GCC has a c++2b switch.
>
>Changes since v1 (13th Jan 2021)
>* New:
>  Test __cplusplus >= 202011L, rather than __cplusplus > 202011L.
>
>* As suggested by Jonathan Wakely:
>  Adjust formatting.
>  Test feature-test macro is defined by <string_view> and <version>.
>  Correct copyright dates on new files.
>  Fix comment typo.
>
>libstdc++-v3/
>
>    Add contains member function to basic_string_view.
>    Likewise to basic_string_view, both with and without _GLIBCXX_USE_CXX11_ABI.
>    Enabled with -std=gnu++20, gnu++2b and c++2b.
>    * include/bits/basic_string.h (basic_string::contains): New.
>    * libstdc++-v3/include/std/string_view (basic_string_view::contains): New.
>    * 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/wchar_t/1.cc:
>New test.

I've committed this to master now.

Now that -std=gnu++23 is supported I changed the preprocessor
condition to just check __cplusplus > 201102L (and not enable it for
-std=gnu++20) and changed the tests to use 23 not 2b. I've attached
what I committed.

Thanks for your patch!



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commit f004d6d9fab9fe732b94f0e7d254700795a37f30
Author: Paul Fee <paul.f.fee@gmail.com>
Date:   Wed Jan 27 12:11:28 2021

    libstdc++: Add string contains member functions for C++2b
    
    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.

diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index e272d332934..bfc97644bd0 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -3073,6 +3073,20 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       { return __sv_type(this->data(), this->size()).ends_with(__x); }
 #endif // C++20
 
+#if __cplusplus > 202002L
+      bool
+      contains(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+
+      bool
+      contains(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+
+      bool
+      contains(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+#endif // C++23
+
       // Allow basic_stringbuf::__xfer_bufptrs to call _M_length:
       template<typename, typename, typename> friend class basic_stringbuf;
     };
@@ -5998,6 +6012,21 @@ _GLIBCXX_END_NAMESPACE_CXX11
       { return __sv_type(this->data(), this->size()).ends_with(__x); }
 #endif // C++20
 
+#if __cplusplus >= 202011L \
+  || (__cplusplus == 202002L && !defined __STRICT_ANSI__)
+      bool
+      contains(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+
+      bool
+      contains(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+
+      bool
+      contains(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).contains(__x); }
+#endif // C++23
+
 # ifdef _GLIBCXX_TM_TS_INTERNAL
       friend void
       ::_txnal_cow_string_C1_for_exceptions(void* that, const char* s,
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index e33e1bc4b79..dba757fad6b 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -352,6 +352,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { return this->ends_with(basic_string_view(__x)); }
 #endif // C++20
 
+#if __cplusplus > 202002L
+#define __cpp_lib_string_contains 202011L
+      constexpr bool
+      contains(basic_string_view __x) const noexcept
+      { return this->find(__x) != npos; }
+
+      constexpr bool
+      contains(_CharT __x) const noexcept
+      { return this->find(__x) != npos; }
+
+      constexpr bool
+      contains(const _CharT* __x) const noexcept
+      { return this->find(__x) != npos; }
+#endif // C++23
+
       // [string.view.find], searching
 
       constexpr size_type
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index e3d52b88c21..ace87cf42cf 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -167,7 +167,7 @@
 #endif
 
 #if __cplusplus > 201703L
-// c++2a
+// c++20
 #define __cpp_lib_atomic_flag_test 201907L
 #define __cpp_lib_atomic_float 201711L
 #define __cpp_lib_atomic_ref 201806L
@@ -256,7 +256,12 @@
 #define __cpp_lib_to_address 201711L
 #define __cpp_lib_to_array 201907L
 #endif
-#endif // C++2a
+
+#if __cplusplus > 202002L
+// c++2b
+#define __cpp_lib_string_contains 202011L
+#endif // C++2b
+#endif // C++20
 #endif // C++17
 #endif // C++14
 #endif // C++11
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/char/1.cc
new file mode 100644
index 00000000000..d313bb553c8
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/char/1.cc
@@ -0,0 +1,65 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do run { target c++23 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// basic_string contains
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+    const std::string haystack("no place for needles");
+
+    VERIFY(haystack.contains(std::string("")));
+    VERIFY(haystack.contains(std::string("no")));
+    VERIFY(haystack.contains(std::string("needles")));
+    VERIFY(haystack.contains(std::string(" for ")));
+    VERIFY(!haystack.contains(std::string("places")));
+
+    VERIFY(haystack.contains(std::string_view("")));
+    VERIFY(haystack.contains(std::string_view("no")));
+    VERIFY(haystack.contains(std::string_view("needles")));
+    VERIFY(haystack.contains(std::string_view(" for ")));
+    VERIFY(!haystack.contains(std::string_view("places")));
+
+    VERIFY(!haystack.contains('\0'));
+    VERIFY(haystack.contains('n'));
+    VERIFY(haystack.contains('e'));
+    VERIFY(haystack.contains('s'));
+    VERIFY(!haystack.contains('x'));
+
+    VERIFY(haystack.contains(""));
+    VERIFY(haystack.contains("no"));
+    VERIFY(haystack.contains("needles"));
+    VERIFY(haystack.contains(" for "));
+    VERIFY(!haystack.contains("places"));
+
+    const std::string nothing;
+    VERIFY(nothing.contains(""));
+    VERIFY(!nothing.contains('\0'));
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/wchar_t/1.cc
new file mode 100644
index 00000000000..14471f97dbd
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/wchar_t/1.cc
@@ -0,0 +1,65 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do run { target c++23 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// basic_string contains
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+    const std::wstring haystack(L"no place for needles");
+
+    VERIFY(haystack.contains(std::wstring(L"")));
+    VERIFY(haystack.contains(std::wstring(L"no")));
+    VERIFY(haystack.contains(std::wstring(L"needles")));
+    VERIFY(haystack.contains(std::wstring(L" for ")));
+    VERIFY(!haystack.contains(std::wstring(L"places")));
+
+    VERIFY(haystack.contains(std::wstring_view(L"")));
+    VERIFY(haystack.contains(std::wstring_view(L"no")));
+    VERIFY(haystack.contains(std::wstring_view(L"needles")));
+    VERIFY(haystack.contains(std::wstring_view(L" for ")));
+    VERIFY(!haystack.contains(std::wstring_view(L"places")));
+
+    VERIFY(!haystack.contains('\0'));
+    VERIFY(haystack.contains('n'));
+    VERIFY(haystack.contains('e'));
+    VERIFY(haystack.contains('s'));
+    VERIFY(!haystack.contains('x'));
+
+    VERIFY(haystack.contains(L""));
+    VERIFY(haystack.contains(L"no"));
+    VERIFY(haystack.contains(L"needles"));
+    VERIFY(haystack.contains(L" for "));
+    VERIFY(!haystack.contains(L"places"));
+
+    const std::wstring nothing;
+    VERIFY(nothing.contains(L""));
+    VERIFY(!nothing.contains('\0'));
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc
index 7445942679b..4f4a8d2c20c 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc
@@ -50,7 +50,7 @@ test01()
 
 int
 main()
-{ 
+{
   test01();
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc
index 5c4e94aba75..022f128a2a0 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc
@@ -50,7 +50,7 @@ test01()
 
 int
 main()
-{ 
+{
   test01();
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/1.cc
new file mode 100644
index 00000000000..9aa87ad6a50
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/1.cc
@@ -0,0 +1,57 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do compile { target c++23 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// basic_string_view contains
+
+#include <string_view>
+
+#ifndef __cpp_lib_string_contains
+# error "Feature-test macro for contains missing in <string_view>"
+#elif __cpp_lib_string_contains != 202011L
+# error "Feature-test macro for contains has wrong value in <string_view>"
+#endif
+
+void
+test01()
+{
+    constexpr std::string_view haystack("no place for needles");
+
+    static_assert(haystack.contains(std::string_view("")));
+    static_assert(haystack.contains(std::string_view("no")));
+    static_assert(haystack.contains(std::string_view("needles")));
+    static_assert(haystack.contains(std::string_view(" for ")));
+    static_assert(!haystack.contains(std::string_view("places")));
+
+    static_assert(!haystack.contains('\0'));
+    static_assert(haystack.contains('n'));
+    static_assert(haystack.contains('e'));
+    static_assert(haystack.contains('s'));
+    static_assert(!haystack.contains('x'));
+
+    static_assert(haystack.contains(""));
+    static_assert(haystack.contains("no"));
+    static_assert(haystack.contains("needles"));
+    static_assert(haystack.contains(" for "));
+    static_assert(!haystack.contains("places"));
+
+    constexpr std::string_view nothing;
+    static_assert(nothing.contains(""));
+    static_assert(!nothing.contains('\0'));
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/2.cc
new file mode 100644
index 00000000000..8a9d783a63a
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/char/2.cc
@@ -0,0 +1,27 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do compile { target c++23 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <version>
+
+#ifndef __cpp_lib_string_contains
+# error "Feature-test macro for contains missing in <string_view>"
+#elif __cpp_lib_string_contains != 202011L
+# error "Feature-test macro for contains has wrong value in <string_view>"
+#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/wchar_t/1.cc
new file mode 100644
index 00000000000..b01bea12384
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/wchar_t/1.cc
@@ -0,0 +1,51 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do compile { target c++23 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// basic_string_view contains
+
+#include <string_view>
+
+void
+test01()
+{
+    constexpr std::wstring_view haystack = L"no place for needles";
+
+    static_assert(haystack.contains(std::wstring_view(L"")));
+    static_assert(haystack.contains(std::wstring_view(L"no")));
+    static_assert(haystack.contains(std::wstring_view(L"needles")));
+    static_assert(haystack.contains(std::wstring_view(L" for ")));
+    static_assert(!haystack.contains(std::wstring_view(L"places")));
+
+    static_assert(!haystack.contains('\0'));
+    static_assert(haystack.contains('n'));
+    static_assert(haystack.contains('e'));
+    static_assert(haystack.contains('s'));
+    static_assert(!haystack.contains('x'));
+
+    static_assert(haystack.contains(L""));
+    static_assert(haystack.contains(L"no"));
+    static_assert(haystack.contains(L"needles"));
+    static_assert(haystack.contains(L" for "));
+    static_assert(!haystack.contains(L"places"));
+
+    constexpr std::wstring_view nothing;
+    static_assert(nothing.contains(L""));
+    static_assert(!nothing.contains('\0'));
+}