libstdc++: Fix stream extraction of IEEE128 long double [PR100912]

The std::__convert_from_v helper that formats double and long double
values into a char buffer was not being duplicated for the two long
double ABIs. This resulted in an ODR violation inside the library, where
some callers needed it to use snprintf to format __ibm128 values and
other callers needed it to use __snprintfieee128 to format __ieee128
values. The linker discarded one of the definitions, leaving one set of
callers using the wrong code.

This puts __convert_from_v in the __gnu_cxx_ieee128 inline namespace
when long double is __ieee128, so that there are two different
definitions of the function.

The std::money_put::__do_put overload for __ibm128 values needs a
different fix, because that is defined when long double is __ieee128 and
so would call the one in the inline namespace. That can be fixed by just
inlining the code directly into the function and using an asm alias to
call the right version of snprintf for the __ibm128 format. The code to
do that can be simpler than __convert_from_v because if we're defining
the ALT128_COMPAT symbols we know that we have a recent glibc and so we
can assume that uselocale and snprintf are supported.

libstdc++-v3/ChangeLog:

	PR libstdc++/100912
	* config/locale/gnu/c_locale.h (__convert_from_v): Use inline
	namespace for IEEE128 long double mode.
	* config/os/gnu-linux/ldbl-ieee128-extra.ver: Add new symbol
	version and export __gnu_cxx_ieee128::__convert_from_v.
	* include/bits/locale_facets_nonio.tcc (money_put::__do_put):
	Make __ibm128 overload use snprintf directly
	* testsuite/util/testsuite_abi.cc: Add new symbol version.
	Remove stable IEEE128/LDBL versions.

1 files changed, 10 insertions, 13 deletions

diff --git a/libstdc++-v3/include/bits/locale_facets_nonio.tcc b/libstdc++-v3/include/bits/locale_facets_nonio.tcc
index 64737823374..98442418f51 100644
--- a/libstdc++-v3/include/bits/locale_facets_nonio.tcc
+++ b/libstdc++-v3/include/bits/locale_facets_nonio.tcc
@@ -635,6 +635,9 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL_OR_CXX11
 
 #if defined _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT \
       && defined __LONG_DOUBLE_IEEE128__
+extern "C"
+__typeof__(__builtin_snprintf) __glibcxx_snprintfibm128 __asm__("snprintf");
+
   template<typename _CharT, typename _OutIter>
     _OutIter
     money_put<_CharT, _OutIter>::
@@ -643,30 +646,24 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL_OR_CXX11
     {
       const locale __loc = __io.getloc();
       const ctype<_CharT>& __ctype = use_facet<ctype<_CharT> >(__loc);
-#if _GLIBCXX_USE_C99_STDIO
       // First try a buffer perhaps big enough.
       int __cs_size = 64;
       char* __cs = static_cast<char*>(__builtin_alloca(__cs_size));
+      const __c_locale __old = __gnu_cxx::__uselocale(_S_get_c_locale());
+
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 328. Bad sprintf format modifier in money_put<>::do_put()
-      int __len = std::__convert_from_v(_S_get_c_locale(), __cs, __cs_size,
-					"%.*Lf", 0, __units);
+      int __len = __glibcxx_snprintfibm128(__cs, __cs_size, "%.*Lf", 0,
+					     __units);
       // If the buffer was not large enough, try again with the correct size.
       if (__len >= __cs_size)
 	{
 	  __cs_size = __len + 1;
 	  __cs = static_cast<char*>(__builtin_alloca(__cs_size));
-	  __len = std::__convert_from_v(_S_get_c_locale(), __cs, __cs_size,
-					"%.*Lf", 0, __units);
+	  __len = __glibcxx_snprintfibm128(__cs, __cs_size, "%.*Lf", 0,
+					     __units);
 	}
-#else
-      // max_exponent10 + 1 for the integer part, + 2 for sign and '\0'.
-      const int __cs_size =
-	__gnu_cxx::__numeric_traits<long double>::__max_exponent10 + 3;
-      char* __cs = static_cast<char*>(__builtin_alloca(__cs_size));
-      int __len = std::__convert_from_v(_S_get_c_locale(), __cs, 0, "%.*Lf", 
-					0, __units);
-#endif
+      __gnu_cxx::__uselocale(__old);
       string_type __digits(__len, char_type());
       __ctype.widen(__cs, __cs + __len, &__digits[0]);
       return __intl ? _M_insert<true>(__s, __io, __fill, __digits)