P0935R0 Eradicating unnecessarily explicit default constructors

This is the last remaining piece of P0935R0. This adds a default
constructor to each of the streambuf and stream types in <sstream> so
that default construction does not use the 'explicit' constructor that
has a single, defaulted argument.

	P0935R0 Eradicating unnecessarily explicit default constructors
	* config/abi/pre/gnu.ver: Tighten existing patterns and export new
	default constructor symbols.
	* include/std/sstream (basic_stringbuf, basic_istringstream)
	(basic_ostringstream, basic_stringstream): Remove default arguments
	from explicit constructors taking ios_base::openmode and add separate
	non-explicit default constructors.
	* testsuite/27_io/basic_istringstream/cons/default.cc: New.
	* testsuite/27_io/basic_ostringstream/cons/default.cc: New.
	* testsuite/27_io/basic_stringstream/cons/default.cc: New.
	* testsuite/27_io/basic_stringbuf/cons/char/default.cc: New.
	* testsuite/27_io/basic_stringbuf/cons/wchar_t/default.cc: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@262474 138bc75d-0d04-0410-961f-82ee72b054a4

Author: redi

libstdc++-v3/ChangeLog

@@ -1,5 +1,18 @@
 2018-07-06  Jonathan Wakely  <[email protected]>
 
+	P0935R0 Eradicating unnecessarily explicit default constructors
+	* config/abi/pre/gnu.ver: Tighten existing patterns and export new
+	default constructor symbols.
+	* include/std/sstream (basic_stringbuf, basic_istringstream)
+	(basic_ostringstream, basic_stringstream): Remove default arguments
+	from explicit constructors taking ios_base::openmode and add separate
+	non-explicit default constructors.
+	* testsuite/27_io/basic_istringstream/cons/default.cc: New.
+	* testsuite/27_io/basic_ostringstream/cons/default.cc: New.
+	* testsuite/27_io/basic_stringstream/cons/default.cc: New.
+	* testsuite/27_io/basic_stringbuf/cons/char/default.cc: New.
+	* testsuite/27_io/basic_stringbuf/cons/wchar_t/default.cc: New.
+
 	* include/std/variant (__accepted_index): Use void_t.
 
 2018-07-05  Jonathan Wakely  <[email protected]>

libstdc++-v3/config/abi/pre/gnu.ver

@@ -1748,10 +1748,20 @@ GLIBCXX_3.4.21 {
     _ZStplI[cw]St11char_traitsI[cw]ESaI[cw]EENSt7__cxx1112basic_stringIT_T0_T1_EE*;
 
     # ABI-tagged stringstreams
-    _ZNSt7__cxx1115basic_stringbuf*;
-    _ZNSt7__cxx1118basic_stringstream*;
-    _ZNSt7__cxx1119basic_istringstream*;
-    _ZNSt7__cxx1119basic_ostringstream*;
+#   _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]*;
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]E[ORS]*;
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]*__xfer_bufptrs*;
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE[a1346789]*;
+#   _ZNSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]*;
+    _ZNSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]E[ORS]*;
+    _ZNSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;
+    _ZNSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[a34]*;
+#   _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]*;
+#   _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]*;
+    _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]E[ORS]*;
+    _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;
+    _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[a34]*;
     _ZNKSt7__cxx1115basic_stringbuf*;
     _ZNKSt7__cxx1118basic_stringstream*;
     _ZNKSt7__cxx1119basic_istringstream*;
@@ -2021,6 +2031,14 @@ GLIBCXX_3.4.26 {
     _ZNSt13runtime_errorC[12]EOS_;
     _ZNSt13runtime_erroraSEOS_;
 
+    # Default constructors for stringstreams
+    _ZNSt15basic_stringbuf[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+    _ZNSt18basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+    _ZNSt19basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+    _ZNSt7__cxx1115basic_stringbuf[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+    _ZNSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+    _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]Ev;
+
 } GLIBCXX_3.4.25;
 
 # Symbols in the support library (libsupc++) have their own tag.

libstdc++-v3/include/std/sstream

@@ -89,6 +89,17 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     public:
       // Constructors:
+
+      /**
+       *  @brief  Starts with an empty string buffer.
+       *
+       *  The default constructor initializes the parent class using its
+       *  own default ctor.
+      */
+      basic_stringbuf()
+      : __streambuf_type(), _M_mode(ios_base::in | ios_base::out), _M_string()
+      { }
+
       /**
        *  @brief  Starts with an empty string buffer.
        *  @param  __mode  Whether the buffer can read, or write, or both.
@@ -97,7 +108,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  own default ctor.
       */
       explicit
-      basic_stringbuf(ios_base::openmode __mode = ios_base::in | ios_base::out)
+      basic_stringbuf(ios_base::openmode __mode)
       : __streambuf_type(), _M_mode(__mode), _M_string()
       { }
 
@@ -401,8 +412,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     public:
       // Constructors:
+
       /**
        *  @brief  Default constructor starts with an empty string buffer.
+       *
+       *  Initializes @c sb using @c in, and passes @c &sb to the base
+       *  class initializer.  Does not allocate any buffer.
+       *
+       *  That's a lie.  We initialize the base class with NULL, because the
+       *  string class does its own memory management.
+      */
+      basic_istringstream()
+      : __istream_type(), _M_stringbuf(ios_base::in)
+      { this->init(&_M_stringbuf); }
+
+      /**
+       *  @brief  Starts with an empty string buffer.
        *  @param  __mode  Whether the buffer can read, or write, or both.
        *
        *  @c ios_base::in is automatically included in @a __mode.
@@ -414,7 +439,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  string class does its own memory management.
       */
       explicit
-      basic_istringstream(ios_base::openmode __mode = ios_base::in)
+      basic_istringstream(ios_base::openmode __mode)
       : __istream_type(), _M_stringbuf(__mode | ios_base::in)
       { this->init(&_M_stringbuf); }
 
@@ -545,8 +570,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     public:
       // Constructors/destructor:
+
       /**
        *  @brief  Default constructor starts with an empty string buffer.
+       *
+       *  Initializes @c sb using @c mode|out, and passes @c &sb to the base
+       *  class initializer.  Does not allocate any buffer.
+       *
+       *  That's a lie.  We initialize the base class with NULL, because the
+       *  string class does its own memory management.
+      */
+      basic_ostringstream()
+      : __ostream_type(), _M_stringbuf(ios_base::out)
+      { this->init(&_M_stringbuf); }
+
+      /**
+       *  @brief  Starts with an empty string buffer.
        *  @param  __mode  Whether the buffer can read, or write, or both.
        *
        *  @c ios_base::out is automatically included in @a mode.
@@ -558,7 +597,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  string class does its own memory management.
       */
       explicit
-      basic_ostringstream(ios_base::openmode __mode = ios_base::out)
+      basic_ostringstream(ios_base::openmode __mode)
       : __ostream_type(), _M_stringbuf(__mode | ios_base::out)
       { this->init(&_M_stringbuf); }
 
@@ -689,19 +728,32 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     public:
       // Constructors/destructors
+
       /**
        *  @brief  Default constructor starts with an empty string buffer.
+       *
+       *  Initializes @c sb using the mode @c in|out, and passes @c &sb
+       *  to the base class initializer.  Does not allocate any buffer.
+       *
+       *  That's a lie.  We initialize the base class with NULL, because the
+       *  string class does its own memory management.
+      */
+      basic_stringstream()
+      : __iostream_type(), _M_stringbuf(ios_base::out | ios_base::in)
+      { this->init(&_M_stringbuf); }
+
+      /**
+       *  @brief  Starts with an empty string buffer.
        *  @param  __m  Whether the buffer can read, or write, or both.
        *
-       *  Initializes @c sb using the mode from @c __m, and passes @c
-       *  &sb to the base class initializer.  Does not allocate any
-       *  buffer.
+       *  Initializes @c sb using the mode from @c __m, and passes @c &sb
+       *  to the base class initializer.  Does not allocate any buffer.
        *
        *  That's a lie.  We initialize the base class with NULL, because the
        *  string class does its own memory management.
       */
       explicit
-      basic_stringstream(ios_base::openmode __m = ios_base::out | ios_base::in)
+      basic_stringstream(ios_base::openmode __m)
       : __iostream_type(), _M_stringbuf(__m)
       { this->init(&_M_stringbuf); }
 

libstdc++-v3/testsuite/27_io/basic_istringstream/cons/default.cc

@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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/>.
+
+// C++11 27.8.3.1  basic_istringstream constructors  [istringstream.cons]
+
+// { dg-do run { target c++11 } }
+
+#include <sstream>
+#include <testsuite_common_types.h>
+
+void test01()
+{
+  // P0935R0
+  __gnu_test::implicitly_default_constructible test;
+  test.operator()<std::istringstream>();
+}
+
+int main() 
+{
+  test01();
+}

libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/default.cc

@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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/>.
+
+// C++11 27.8.4.1  basic_ostringstream constructors  [ostringstream.cons]
+
+// { dg-do run { target c++11 } }
+
+#include <sstream>
+#include <testsuite_common_types.h>
+
+void test01()
+{
+  // P0935R0
+  __gnu_test::implicitly_default_constructible test;
+  test.operator()<std::ostringstream>();
+}
+
+int main() 
+{
+  test01();
+}

libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/default.cc

@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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/>.
+
+// C++11 27.8.2.1  basic_stringbuf constructors  [stringbuf.cons]
+
+// { dg-do run { target c++11 } }
+
+#include <sstream>
+#include <testsuite_common_types.h>
+
+void test01()
+{
+  // P0935R0
+  __gnu_test::implicitly_default_constructible test;
+  test.operator()<std::stringbuf>();
+}
+
+int main() 
+{
+  test01();
+}

libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/default.cc

@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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/>.
+
+// C++11 27.8.2.1  basic_stringbuf constructors  [stringbuf.cons]
+
+// { dg-do run { target c++11 } }
+
+#include <sstream>
+#include <testsuite_common_types.h>
+
+void test01()
+{
+  // P0935R0
+  __gnu_test::implicitly_default_constructible test;
+  test.operator()<std::wstringbuf>();
+}
+
+int main() 
+{
+  test01();
+}

libstdc++-v3/testsuite/27_io/basic_stringstream/cons/default.cc

@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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/>.
+
+// C++11 27.8.5.1  basic_stringstream constructors  [stringstream.cons]
+
+// { dg-do run { target c++11 } }
+
+#include <sstream>
+#include <testsuite_common_types.h>
+
+void test01()
+{
+  // P0935R0
+  __gnu_test::implicitly_default_constructible test;
+  test.operator()<std::stringstream>();
+}
+
+int main() 
+{
+  test01();
+}