Re: [patch] libstdc++/65352 fix ubsan errors in std::array

[Jonathan Wakely]

On 28/05/15 12:53 +0100, Jonathan Wakely wrote:

Unsurprisingly ubsan doesn't like referencing a null pointer.

With this change __array_traits::_S_ref is only used to access an
element, which is invalid for std::array<T, 0> anyway.

Tested powerpc64le-linux, committed to trunk.

I forgot the debug and profile modes, fixed like so.

1) Why do we even have _profile::array? What's it for?

2) If we could run 'make check-sanitize' I could have added tests for
  this bug, and could have found it still failed in debug and profile
  modes. We need to be able to run the testsuite with ubsan.

I'll commit it to trunk and gcc-5-branch after testing.


commit 7a673c403d77fb2c57620f5e4f027b679bf69635
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu May 28 15:35:43 2015 +0100

    	PR libstdc++/65352
    	* include/profile/array (array::data): Use _S_ptr.
    	* include/debug/array (array::data): Likewise.

diff --git a/libstdc++-v3/include/debug/array b/libstdc++-v3/include/debug/array
index 31d146e..411e816 100644
--- a/libstdc++-v3/include/debug/array
+++ b/libstdc++-v3/include/debug/array
@@ -216,11 +216,11 @@ namespace __debug
 
       pointer
       data() noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
 
       const_pointer
       data() const noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
     };
 
   // Array comparisons.
diff --git a/libstdc++-v3/include/profile/array b/libstdc++-v3/include/profile/array
index a90e396..5198bb3 100644
--- a/libstdc++-v3/include/profile/array
+++ b/libstdc++-v3/include/profile/array
@@ -178,11 +178,11 @@ namespace __profile
 
       pointer
       data() noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
 
       const_pointer
       data() const noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
     };
 
   // Array comparisons.