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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/103387] powerpc64le: segmentation fault on std::cout
 with ieee128 long double variable
Date: Tue, 28 Mar 2023 16:48:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103387

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This fixes the testcase, but I'll check for other problems using the cached
facets:

--- a/libstdc++-v3/include/bits/ostream.tcc
+++ b/libstdc++-v3/include/bits/ostream.tcc
@@ -69,7 +69,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            ios_base::iostate __err =3D ios_base::goodbit;
            __try
              {
+#ifndef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
                const __num_put_type& __np =3D __check_facet(this->_M_num_p=
ut);
+#else
+               const __num_put_type& __np
+                 =3D use_facet<__num_put_type>(this->_M_ios_locale);
+#endif
                if (__np.put(*this, *this, this->fill(), __v).failed())
                  __err |=3D ios_base::badbit;
              }

The _M_num_put cache exists to avoid doing the RTTI check implied by use_fa=
cet
every time we use the stream. But that RTTI check has been removed for GCC =
13
anyway. Since the cached facet is the cause of this bug, we can just ignore=
 it
for powercp64le when we support two forms of long double.=