[gcc r12-5342] libstdc++: Fix std::type_info::before for ARM [PR103240]

[Jonathan Wakely]

https://gcc.gnu.org/g:054bf99841aad3869c70643b2ba2d9f85770c980

commit r12-5342-g054bf99841aad3869c70643b2ba2d9f85770c980
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Nov 16 21:03:21 2021 +0000

    libstdc++: Fix std::type_info::before for ARM [PR103240]
    
    The r179236 fix for std::type_info::operator== should also have been
    applied to std::type_info::before. Otherwise two distinct types can
    compare equivalent due to using a string comparison, when they should do
    a pointer comparison.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/103240
            * libsupc++/tinfo2.cc (type_info::before): Use unadjusted name
            to check for the '*' prefix.
            * testsuite/util/testsuite_shared.cc: Add type_info object for
            use in new test.
            * testsuite/18_support/type_info/103240.cc: New test.

Diff:
---
 libstdc++-v3/libsupc++/tinfo2.cc                   |  5 ++-
 .../testsuite/18_support/type_info/103240.cc       | 36 ++++++++++++++++++++++
 libstdc++-v3/testsuite/util/testsuite_shared.cc    | 12 ++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/libsupc++/tinfo2.cc b/libstdc++-v3/libsupc++/tinfo2.cc
index b587cfd037b..d02021fe538 100644
--- a/libstdc++-v3/libsupc++/tinfo2.cc
+++ b/libstdc++-v3/libsupc++/tinfo2.cc
@@ -36,7 +36,10 @@ type_info::before (const type_info &arg) const _GLIBCXX_NOEXCEPT
 #if __GXX_MERGED_TYPEINFO_NAMES
   return name () < arg.name ();
 #else
-  return (name ()[0] == '*') ? name () < arg.name ()
+  /* The name() method will strip any leading '*' prefix. Therefore
+     take care to look at __name rather than name() when looking for
+     the "pointer" prefix.  */
+  return (__name[0] == '*') ? name () < arg.name ()
     :  __builtin_strcmp (name (), arg.name ()) < 0;
 #endif
 }
diff --git a/libstdc++-v3/testsuite/18_support/type_info/103240.cc b/libstdc++-v3/testsuite/18_support/type_info/103240.cc
new file mode 100644
index 00000000000..3d5968ac25c
--- /dev/null
+++ b/libstdc++-v3/testsuite/18_support/type_info/103240.cc
@@ -0,0 +1,36 @@
+// { dg-do run }
+// { dg-require-sharedlib "" }
+// { dg-options "./testsuite_shared.so" }
+
+#include <typeinfo>
+#include <testsuite_hooks.h>
+
+namespace __gnu_test
+{
+namespace
+{
+  struct S { };
+  struct T { };
+}
+
+// Defined in testsuite_shared.so, referring to private type in that library
+// with the same mangled name as __gnu_test::<anonymous>::S defined here.
+extern const std::type_info& pr103240_private_S;
+}
+
+const std::type_info& private_S = __gnu_test::pr103240_private_S;
+const std::type_info& local_S = typeid(__gnu_test::S);
+const std::type_info& local_T = typeid(__gnu_test::T);
+
+int main()
+{
+  VERIFY( local_S == local_S );
+  VERIFY( ! local_S.before(local_S) );
+
+  VERIFY( local_S != local_T );
+  VERIFY( local_S.before(local_T) || local_T.before(local_S) );
+
+  VERIFY( local_S != private_S );
+  // PR libstdc++/103240
+  VERIFY( local_S.before(private_S) || private_S.before(local_S) );
+}
diff --git a/libstdc++-v3/testsuite/util/testsuite_shared.cc b/libstdc++-v3/testsuite/util/testsuite_shared.cc
index c4a7ed4abe5..8c10534c511 100644
--- a/libstdc++-v3/testsuite/util/testsuite_shared.cc
+++ b/libstdc++-v3/testsuite/util/testsuite_shared.cc
@@ -23,6 +23,9 @@
 #include <map>
 #include <ext/mt_allocator.h>
 #include <bits/functexcept.h>
+#if __cpp_rtti
+# include <typeinfo>
+#endif
 
 namespace __gnu_test
 {
@@ -130,4 +133,13 @@ try_function_random_fail()
   }
 #endif
 
+#if __cpp_rtti
+// PR libstdc++/103240
+namespace
+{
+  struct S { };
+}
+const std::type_info& pr103240_private_S = typeid(S);
+#endif
+
 } // end namepace __gnu_test