[Bug libstdc++/64560] New: [5 Regression] building libstdc++ with -fno-rtti fails in new cxx11-shim-facets.cc file

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64560

            Bug ID: 64560
           Summary: [5 Regression] building libstdc++ with -fno-rtti fails
                    in new cxx11-shim-facets.cc file
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

Someone on IRC pointed out that the build fails when configuring with
--enable-cxx-flags=-fno-rtti 

In file included from
/home/jwakely/src/gcc/libstdc++-v3/src/c++11/cow-shim_facets.cc:35:0:
/home/jwakely/src/gcc/libstdc++-v3/src/c++11/cxx11-shim_facets.cc: In member
function ‘const std::locale::facet* std::locale::facet::_M_cow_shim(const
std::locale::id*) const’:
/home/jwakely/src/gcc/libstdc++-v3/src/c++11/cxx11-shim_facets.cc:772:51:
error: ‘dynamic_cast’ not permitted with -fno-rtti
     if (auto* p = dynamic_cast<const __shim*>(this))
                                                   ^
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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++/64560] [5 Regression] building libstdc++ with -fno-rtti fails in new cxx11-shim-facets.cc file
Date: Sun, 11 Jan 2015 15:23:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd560

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
--- a/libstdc++-v3/src/c++11/cxx11-shim_facets.cc
+++ b/libstdc++-v3/src/c++11/cxx11-shim_facets.cc
@@ -768,9 +768,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   {
     using namespace __facet_shims;

+#if __cpp_rtti
     // If this is already a shim just use its underlying facet.
     if (auto* p = dynamic_cast<const __shim*>(this))
       return p->_M_get();
+#endif

     if (which == &numpunct<char>::id)
       return new numpunct_shim<char>{this};