Re: c++/10307: constructor for static object of template omitted

[bangerth at dealii dot org]

Synopsis: constructor for static object of template omitted

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Thu Apr  3 22:23:54 2003
State-Changed-Why:
    Behavior confirmed with all versions of gcc (2.95 .. 3.4).
    Another testcase is this:
    ----------------------
    #include <iostream>
    
    // ------------- template
    
    int template_counter = 0;
    
    struct TemplateStatic {
        TemplateStatic () { ++template_counter; }
    };
    
    template <typename T> struct Template {
        static TemplateStatic s;
    };
    template <typename T> TemplateStatic Template<T>::s;
    
    // ------------ non-template
    
    int non_template_counter = 0;
    
    struct NonTemplateStatic {
        NonTemplateStatic () { ++non_template_counter; }
    };
    
    struct NonTemplate {
        static NonTemplateStatic s;
    };
    NonTemplateStatic NonTemplate::s;
    
    // ------------- use both
    
    int main() {
      Template<int> t;
      NonTemplate   nt;
    
      std::cout << template_counter << " "
                << non_template_counter << std::endl;
    }
    ---------------------------
    
    Both Template and NonTemplate have a static variable,
    but the constructor of them is only run for the non-template.
    
    I think this is actually what the standard prescribes,
    since static variables are only instantiated by use or
    by explicit instantiation, not by instantiation of
    the class they belong to. In fact, you can make the above
    code work as you expect it by adding this line:
      template TemplateStatic Template<int>::s;
    
    Maybe someone of those with more knowledge of these matters
    can confirm my interpretation?
    
    Regards
      Wolfgang
    
    PS: icc7 agrees with gcc in all this, so I'd say it's not
    a bug.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10307