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From Martin Sebor <>
Subject [Fwd: [jira] Created: (STDCXX-985) [Linux/gcc] 20.meta.rel.cpp fails is_base_of assertions]
Date Wed, 02 Jul 2008 22:34:23 GMT
Before you create too many of these, the Component for compiler
bugs should be External so we can tell them from bugs in our own


-------- Original Message --------
Subject: [jira] Created: (STDCXX-985) [Linux/gcc] 20.meta.rel.cpp fails 
is_base_of assertions
Date: Wed, 2 Jul 2008 15:24:45 -0700 (PDT)
From: Travis Vitek (JIRA) <>

[Linux/gcc] 20.meta.rel.cpp fails is_base_of assertions

                  Key: STDCXX-985
              Project: C++ Standard Library
           Issue Type: Bug
           Components: TR1.4 - Metaprogramming and Type Traits
     Affects Versions: 4.3
          Environment: gcc-4.3
             Reporter: Travis Vitek
              Fix For: 4.3

The {{__is_base_of()}} helper provided with gcc-4.3 doesn't detect 
protected and private inheritance as required by the draft standard. It 
appears that the helper may be based on an older version of the standard 
and needs to be updated. Here is a note from the description of the 
{{is_base_of}} trait.
{quote}[Note:Base classes that are private, protected, or ambigious are, 
nonetheless, base classes. —end note ]{quote}

This is the gcc description of the helper that they provide..
{quote}__is_base_of (base_type, derived_type)
If base_type is a base class of derived_type ([class.derived]) then the 
trait is true, otherwise it is false. Top-level cv qualifications of 
base_type and derived_type are ignored. For the purposes of this trait, 
a class type is considered is own base. Requires: if __is_class 
(base_type) and __is_class (derived_type) are true and base_type and 
derived_type are not the same type (disregarding cv-qualifiers), 
derived_type shall be a complete type. Diagnostic is produced if this 
requirement is not met.{quote}

Since there is no way to detect this from within the library, there 
isn't much we can do about fixing it.

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