[cfe-dev] On instantiations of template declarations.

[Abramo Bagnara]

Il 01/06/2010 17:44, Douglas Gregor ha scritto:
> 
> On Jun 1, 2010, at 7:38 AM, Enea Zaffanella wrote:
>> Consider now the following variant, where we have a static data member:
>>
>> template <typename T>
>> struct A { static int a; };
>>
>> template <typename T>
>> int A<T>::a = 0;
>>
>> A<int> si;
>> A<double> sd;
>>
>> void bar() {
>>   sd.a = 13;
>> }
>>
>> Here, we have two implicit instantiations of the template A.
>> Each of those declares the corresponding static data member.
>> For one of those (A<double>), we also have an implicit instantiation of 
>> the *definition* of the static data member A<double>::a.
>> This implicit definition is reachable starting from the implicit 
>> declaration using method:
>>
>>   VarDecl* VarDecl::getOutOfLineDefinition();
>>   If this is a static data member, find its out-of-line definition.
>>
>> Strangely, the very same implicit definition is also listed in the 
>> context of the translation unit. This can be seen when dumping the AST, 
>> just after the definition of function bar():
>>
>> ===================
>> [...]
>> void bar() (CompoundStmt 0x2151fb0 <var_template.cc:10:12, line:12:1>
>>   (BinaryOperator 0x216be70 <line:11:3, col:10> 'int' '='
>>     (MemberExpr 0x216bdf0 <col:3, col:6> 'int' .a 0x216b160
>>       (DeclRefExpr 0x216bdb0 <col:3> 'A<double>':'struct A<double>' 
>> Var='sd' 0x216ae10))
>>     (IntegerLiteral 0x216be30 <col:10> 'int' 13)))
>>
>>
>> static int a = (IntegerLiteral 0x216a8d0 <var_template.cc:5:15> 'int' 0)
>> ;
>> ===================
>>
>> So, finally, our question is: why such a difference?
>>
>> That is, why does the translation unit context contains these 
>> (implicitly instantiated) definitions of static data members?
>> It was not containing the (implicitly instantiated) specialization of 
>> the class template ... or of its methods.
> 
> Definitely a bug. Implicit instantiations should not show up in the translation unit context.

The attached patch should fix this, right? Should I commit it?

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