[Bug c++/42840] New: const-ref argument in a variadic template arglist is mishandled

["navin dot kumar at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

When a static-const primitive is passed as a const-ref argument to function
with a variadic template arglist, GCC generates code that references the
static-const primitive, and optimizes away the static-const primitive,
resulting in a "undefined reference" linker error.

/* Start of Example */
class Foo {
public:
    template <typename... T>
    static void foo(const T&... blah) { }
};

class Test {
public:
    static const int tmp = 1;
};

int main(int argc, char** argv) {
    Foo::foo(Test::tmp); // THIS COMPILES BUT LINKER FAILS
    //Foo::foo(static_cast<int>(Test::tmp)); // THIS COMPILES AND LINKS FINE
}
/* END OF EXAMPLE */

LINKER ERROR:
/tmp/ccfV1opu.o: In function `main':
tmp.cc:(.text+0x10): undefined reference to `Test::tmp'
collect2: ld returned 1 exit status

Since static cast of the static-const int primitive to an int fixes the
problem, it's clear that GCC is somehow mishandling how it optimizes away
Test::tmp even though it's being used as a const int& in Foo::foo(...)


-- 
           Summary: const-ref argument in a variadic template arglist is
                    mishandled
           Product: gcc
           Version: 4.3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: navin dot kumar at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42840