[PATCH] Add xfail-if to some tests that fail with COW strings

[Jonathan Wakely]

These tests fail when run with -D_GLIBCXX_USE_CXX11_ABI=0 

        * testsuite/21_strings/basic_string/cons/char/deduction.cc: XFAIL for
        COW strings.
        * testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc:
        Likewise.
        * testsuite/21_strings/basic_string/requirements/
        explicit_instantiation/debug.cc: Likewise.
Tested powerpc64le-linux, committed to trunk.

commit 643a1bb749c54ecc5faed9c675d7f4a29cfbea6a
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Jul 5 17:44:09 2018 +0100

    Add xfail-if to some tests that fail with COW strings
    
    These tests fail when run with -D_GLIBCXX_USE_CXX11_ABI=0
    
            * testsuite/21_strings/basic_string/cons/char/deduction.cc: XFAIL 
for
            COW strings.
            * testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc:
            Likewise.
            * testsuite/21_strings/basic_string/requirements/
            explicit_instantiation/debug.cc: Likewise.

diff --git 
a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/deduction.cc 
b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/deduction.cc
index fc28467e29b..4662fbd4b4d 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/deduction.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/deduction.cc
@@ -17,6 +17,7 @@
 
 // { dg-options "-std=gnu++17" }
 // { dg-do compile { target c++17 } }
+// { dg-xfail-if "COW string missing deduction guides" { ! cxx11-abi } }
 
 #include <string>
 #include <testsuite_iterators.h>
diff --git 
a/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc 
b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc
index c40651f13db..7740af51123 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc
@@ -17,6 +17,7 @@
 
 // { dg-options "-std=gnu++17" }
 // { dg-do compile { target c++17 } }
+// { dg-xfail-if "COW string missing deduction guides" { ! cxx11-abi } }
 
 #include <string>
 #include <testsuite_iterators.h>
diff --git 
a/libstdc++-v3/testsuite/21_strings/basic_string/requirements/explicit_instantiation/debug.cc
 
b/libstdc++-v3/testsuite/21_strings/basic_string/requirements/explicit_instantiation/debug.cc
index a166a9b1d58..20b8f59ba3d 100644
--- 
a/libstdc++-v3/testsuite/21_strings/basic_string/requirements/explicit_instantiation/debug.cc
+++ 
b/libstdc++-v3/testsuite/21_strings/basic_string/requirements/explicit_instantiation/debug.cc
@@ -20,8 +20,9 @@
 #include <debug/string>
 
 // { dg-do compile }
+// { dg-xfail-if "COW string missing some required members" { ! cxx11-abi } }
 
 // libstdc++/21770
 namespace debug = __gnu_debug;
-template class debug::basic_string<int, std::char_traits<int>, 
+template class debug::basic_string<int, std::char_traits<int>,
                                   std::allocator<char> >;