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Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.

From: Jonathan Wakely <jwakely at redhat dot com>
To: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
Cc: Rüdiger Sonderfeld <ruediger at c-plusplus dot de>, Luke Allardyce <lukeallardyce at gmail dot com>
Date: Mon, 6 Oct 2014 16:56:15 +0100
Subject: Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.
Authentication-results: sourceware.org; auth=none
References: <20140327133723 dot GA13599 at redhat dot com> <1901588 dot qodTErPe42 at descartes> <20140327162714 dot GA13192 at redhat dot com> <CAFW6PZC0u5=i-KqQZZsbkmg5iWr6u2WVnnBQVqG8V2Bt6oOzOg at mail dot gmail dot com>

On 28/03/14 08:56 +0900, Luke Allardyce wrote:

It looks like the new standard also requires the precision to be
ignored for hexfloat

For conversion from a floating-point type, if floatfield != (ios_base::fixed | ios_base:: scientific), str.precision() is specified as precision in the conversion specification. Otherwise, no precision is specified.


I've made this change and adjusted the test so that it doesn't make
any assumptions about the exact format of hexadecimal float output, as
it's unspecified whether you get e.g. 0x1.ep+3 or 0xfp+0 for 15.

As Luke pointed out, this changes the behaviour of some valid C++03
programs, but I think that's the right thing to do in this case. I'll
document that in the release notes.

Tested x86_64-linux, committed to trunk.

commit 7090c2fca0e3858ea527b66a1eb44fd504f1ba4e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Sep 22 23:10:54 2014 +0100

    2014-10-06  RÃdiger Sonderfeld  <ruediger@c-plusplus.de>
    	    Jonathan Wakely  <jwakely@redhat.com>
    
    	PR libstdc++/59987
    	* doc/xml/manual/status_cxx2011.xml: Remove hexfloat from notes.
    	* doc/html/manual/status.html: Regenerate.
    	* include/bits/ios_base.h (hexfloat): New function.
    	(defaultfloat): New function.
    	* src/c++98/locale_facets.cc (__num_base::_S_format_float): Support
    	hexadecimal floating point format.
    	* testsuite/27_io/basic_ostream/inserters_arithmetic/char/hexfloat.cc:
    	New file.

diff --git a/libstdc++-v3/doc/xml/manual/status_cxx2011.xml b/libstdc++-v3/doc/xml/manual/status_cxx2011.xml
index 5b36556..108de36 100644
--- a/libstdc++-v3/doc/xml/manual/status_cxx2011.xml
+++ b/libstdc++-v3/doc/xml/manual/status_cxx2011.xml
@@ -2131,7 +2131,6 @@ particular release.
       <entry>
         Missing <code>io_errc</code> and <code>iostream_category</code>.
         <code>ios_base::failure</code> is not derived from <code>system_error</code>.
-	Missing <code>ios_base::hexfloat</code>.
       </entry>
     </row>
     <row>
diff --git a/libstdc++-v3/include/bits/ios_base.h b/libstdc++-v3/include/bits/ios_base.h
index fb448fd..5e33b81 100644
--- a/libstdc++-v3/include/bits/ios_base.h
+++ b/libstdc++-v3/include/bits/ios_base.h
@@ -984,6 +984,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     return __base;
   }
 
+#if __cplusplus >= 201103L
+  // New C++11 floatfield manipulators
+
+  /// Calls
+  /// base.setf(ios_base::fixed|ios_base::scientific, ios_base::floatfield)
+  inline ios_base&
+  hexfloat(ios_base& __base)
+  {
+    __base.setf(ios_base::fixed | ios_base::scientific, ios_base::floatfield);
+    return __base;
+  }
+
+  /// Calls @c base.unsetf(ios_base::floatfield)
+  inline ios_base&
+  defaultfloat(ios_base& __base)
+  {
+    __base.unsetf(ios_base::floatfield);
+    return __base;
+  }
+#endif
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
diff --git a/libstdc++-v3/src/c++98/locale_facets.cc b/libstdc++-v3/src/c++98/locale_facets.cc
index 3669acb..7ed04e6 100644
--- a/libstdc++-v3/src/c++98/locale_facets.cc
+++ b/libstdc++-v3/src/c++98/locale_facets.cc
@@ -69,19 +69,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     if (__flags & ios_base::showpoint)
       *__fptr++ = '#';
 
-    // As per DR 231: _always_, not only when 
-    // __flags & ios_base::fixed || __prec > 0
-    *__fptr++ = '.';
-    *__fptr++ = '*';
+    ios_base::fmtflags __fltfield = __flags & ios_base::floatfield;
+
+    if (__fltfield != (ios_base::fixed | ios_base::scientific))
+      {
+        // As per DR 231: not only when __flags & ios_base::fixed || __prec > 0
+        *__fptr++ = '.';
+        *__fptr++ = '*';
+      }
 
     if (__mod)
       *__fptr++ = __mod;
-    ios_base::fmtflags __fltfield = __flags & ios_base::floatfield;
     // [22.2.2.2.2] Table 58
     if (__fltfield == ios_base::fixed)
       *__fptr++ = 'f';
     else if (__fltfield == ios_base::scientific)
       *__fptr++ = (__flags & ios_base::uppercase) ? 'E' : 'e';
+#ifdef _GLIBCXX_USE_C99
+    else if (__fltfield == (ios_base::fixed | ios_base::scientific))
+      *__fptr++ = (__flags & ios_base::uppercase) ? 'A' : 'a';
+#endif
     else
       *__fptr++ = (__flags & ios_base::uppercase) ? 'G' : 'g';
     *__fptr = '\0';
diff --git a/libstdc++-v3/testsuite/27_io/basic_ostream/inserters_arithmetic/char/hexfloat.cc b/libstdc++-v3/testsuite/27_io/basic_ostream/inserters_arithmetic/char/hexfloat.cc
new file mode 100644
index 0000000..485a485
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostream/inserters_arithmetic/char/hexfloat.cc
@@ -0,0 +1,152 @@
+// { dg-options "-std=gnu++11" }
+
+// 2014-03-27 RÃdiger Sonderfeld
+// test the hexadecimal floating point inserters (facet num_put)
+
+// Copyright (C) 2014 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 <iomanip>
+#include <sstream>
+#include <string>
+#include <testsuite_hooks.h>
+
+#ifndef _GLIBCXX_ASSERT
+#  define TEST_NUMPUT_VERBOSE 1
+#endif
+
+#ifdef TEST_NUMPUT_VERBOSE
+#  include <iostream>
+#endif
+
+using namespace std;
+
+void
+test01()
+{
+  ostringstream os;
+  double d = 272.; // 0x1.1p+8;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << os.precision() << endl;
+#endif
+  os << hexfloat << setprecision(1);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stod(os.str()) == d );
+  VERIFY( os.str().substr(0, 2) == "0x" );
+  VERIFY( os.str().find('p') != std::string::npos );
+
+  os.str("");
+  os << uppercase << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stod(os.str()) == d );
+  VERIFY( os.str().substr(0, 2) == "0X" );
+  VERIFY( os.str().find('P') != std::string::npos );
+
+  os << nouppercase;
+  os.str("");
+  os << defaultfloat << setprecision(6);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && os.str() == "272" );
+
+  os.str("");
+  d = 15.; //0x1.ep+3;
+  os << hexfloat << setprecision(1);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stod(os.str()) == d );
+  os.str("");
+  os << uppercase << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stod(os.str()) == d );
+  os << nouppercase;
+  os.str("");
+  os << defaultfloat << setprecision(6);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && os.str() == "15" );
+}
+
+void
+test02()
+{
+  ostringstream os;
+  long double d = 272.L; // 0x1.1p+8L;
+  os << hexfloat << setprecision(1);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stold(os.str()) == d );
+  os.str("");
+  os << uppercase << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stold(os.str()) == d );
+  os << nouppercase;
+  os.str("");
+  os << defaultfloat << setprecision(6);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && os.str() == "272" );
+
+  os.str("");
+  os << hexfloat << setprecision(1);
+  d = 15.; //0x1.ep+3;
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stold(os.str()) == d );
+  os.str("");
+  os << uppercase << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && std::stold(os.str()) == d );
+  os << nouppercase;
+  os.str("");
+  os << defaultfloat << setprecision(6);
+  os << d;
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "got: " << os.str() << endl;
+#endif
+  VERIFY( os && os.str() == "15" );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}

Follow-Ups:
- Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.
  - From: Andreas Schwab
- Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.
  - From: Rainer Orth

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