From: Paolo Carlini <pcarlini@unitus.it>
Date: Mon, 6 Jan 2003 15:51:49 +0000 (+0100)
Subject: re PR libstdc++/9151 (std::setprecision limited to 16 digits when outputting a double... 
X-Git-Tag: releases/gcc-3.2.2~138
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4b2ba0956dde87cc5e6de0c5893ddcd13236f47;p=thirdparty%2Fgcc.git

re PR libstdc++/9151 (std::setprecision limited to 16 digits when outputting a double to a stream)

2003-01-06  Paolo Carlini  <pcarlini@unitus.it>

	PR libstdc++/9151
	* include/bits/locale_facets.cc (num_put::_M_convert_float):
	Limit __prec to digits10 + 2, not digits10 + 1, taking into
	account the possibility of %{g,G} conversion specifiers
	inside _S_format_float.
	* testsuite/27_io/ostream_inserter_arith.cc (test06): Add.

From-SVN: r60941
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 09d86d8676f0..0cd1b50a19b8 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2003-01-06  Paolo Carlini  <pcarlini@unitus.it>
+
+	PR libstdc++/9151
+	* include/bits/locale_facets.cc (num_put::_M_convert_float):
+	Limit __prec to digits10 + 2, not digits10 + 1, taking into
+	account the possibility of %{g,G} conversion specifiers
+	inside _S_format_float.
+	* testsuite/27_io/ostream_inserter_arith.cc (test06): Add.
+
 2003-01-06  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* testsuite/lib/libstdc++-v3-dg.exp (libstdc++-v3-init):
diff --git a/libstdc++-v3/include/bits/locale_facets.tcc b/libstdc++-v3/include/bits/locale_facets.tcc
index ce6f3d7d5ffa..1bf3d7ce7962 100644
--- a/libstdc++-v3/include/bits/locale_facets.tcc
+++ b/libstdc++-v3/include/bits/locale_facets.tcc
@@ -622,9 +622,14 @@ namespace std
       _M_convert_float(_OutIter __s, ios_base& __io, _CharT __fill, char __mod,
 		       _ValueT __v) const
       {
-	// Note: digits10 is rounded down.  We need to add 1 to ensure
+	// Note: digits10 is rounded down: we need to add 1 to ensure
 	// we get the full available precision.
-	const int __max_digits = numeric_limits<_ValueT>::digits10 + 1;
+	// Then, in general, one more 1 needs to be added since, when the
+	// %{g,G} conversion specifiers are chosen inside _S_format_float, the
+	// precision field is "the maximum number of significant digits", *not*
+	// the "number of digits to appear after the decimal point", as happens
+	// for %{e,E,f,F} (C99, 7.19.6.1,4).
+	const int __max_digits = numeric_limits<_ValueT>::digits10 + 2;
 	streamsize __prec = __io.precision();
 
 	if (__prec > static_cast<streamsize>(__max_digits))
@@ -1628,7 +1633,7 @@ namespace std
 	  // Find smallest matching string.
 	  size_t __minlen = 10;
 	  for (size_t __i2 = 0; __i2 < __nmatches; ++__i2)
-	    __minlen = min(__minlen, 
+	    __minlen = min(__minlen,
 			   __traits_type::length(__names[__matches[__i2]]));
 	  
 	  if (__pos < __minlen && __beg != __end)
diff --git a/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc b/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc
index 041f3149011f..e4e618d68d86 100644
--- a/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc
+++ b/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc
@@ -368,7 +368,26 @@ test05()
   istringstream istr (sval);
   double d;
   istr >> d;
-  VERIFY (abs(pi-d)/pi < DBL_EPSILON);
+  VERIFY( abs(pi-d)/pi < DBL_EPSILON );
+  return 0;
+}
+
+
+// libstdc++/9151
+int
+test06()
+{
+  int prec = numeric_limits<double>::digits10 + 2;
+  double oval = numeric_limits<double>::min();
+
+  stringstream ostr;
+  ostr.precision(prec);
+  ostr << oval;
+  string sval = ostr.str();
+  istringstream istr (sval);
+  double ival;
+  istr >> ival;
+  VERIFY( abs(oval-ival)/oval < DBL_EPSILON ); 
   return 0;
 }
 
@@ -380,6 +399,7 @@ main()
   test03();
   test04();
   test05();
+  test06();
 #ifdef TEST_NUMPUT_VERBOSE
   cout << "Test passed!" << endl;
 #endif