PR libstdc++/68737 Do not use vsnprintf on HPUX

It doesn't conform to the spec, so use vsprintf with a large buffer
instead.

	PR libstdc++/68737
	* config/locale/generic/c_locale.h (__convert_from_v)
	[_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
	* config/os/hpux/os_defines.h: Define _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
	* include/bits/locale_facets.tcc (num_put::_M_insert_float)
	[_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.

From-SVN: r268350

libstdc++-v3/ChangeLog

+2019-01-28  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/68737
+	* config/locale/generic/c_locale.h (__convert_from_v)
+	[_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
+	* config/os/hpux/os_defines.h: Define _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
+	* include/bits/locale_facets.tcc (num_put::_M_insert_float)
+	[_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
+
 2019-01-24  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/88840

libstdc++-v3/config/locale/generic/c_locale.h

@@ -70,7 +70,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __builtin_va_list __args;
     __builtin_va_start(__args, __fmt);
 
-#if _GLIBCXX_USE_C99_STDIO
+#if _GLIBCXX_USE_C99_STDIO && !_GLIBCXX_HAVE_BROKEN_VSNPRINTF
     const int __ret = __builtin_vsnprintf(__out, __size, __fmt, __args);
 #else
     const int __ret = __builtin_vsprintf(__out, __fmt, __args);

libstdc++-v3/config/os/hpux/os_defines.h

@@ -109,4 +109,9 @@ typedef long int __padding_type;
 #if defined (__hppa__)
 #define _GLIBCXX_HAVE_BROKEN_STRTOLD 1
 #endif
+
+// The vnsprintf function returns -1 when the buffer is too small.
+// See PR libstdc++/68737.
+#define _GLIBCXX_HAVE_BROKEN_VSNPRINTF 1
+
 #endif

libstdc++-v3/include/bits/locale_facets.tcc

@@ -992,7 +992,7 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL
 	char __fbuf[16];
 	__num_base::_S_format_float(__io, __fbuf, __mod);
 
-#if _GLIBCXX_USE_C99_STDIO
+#if _GLIBCXX_USE_C99_STDIO && !_GLIBCXX_HAVE_BROKEN_VSNPRINTF
 	// Precision is always used except for hexfloat format.
 	const bool __use_prec =
 	  (__io.flags() & ios_base::floatfield) != ios_base::floatfield;