[Linux/gcc] 20.meta.rel.cpp fails is_base_of assertions
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Key: STDCXX-985
URL: https://issues.apache.org/jira/browse/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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