[Bug c++/84373] New: g++ incorrectly resolves names for default parameters

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84373

            Bug ID: 84373
           Summary: g++ incorrectly resolves names for default parameters
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: smcallis at gmail dot com
  Target Milestone: ---

Created attachment 43409
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43409&action=edit
Reproduction of issue

Code is attached, the gist is that when defining a default parameter, gcc
allows you to refer to a global variable with the same name, whereas the spec
would indicate that the function parameters should be included in the name
lookup and cause an error.

Stackoverflow reference:
https://stackoverflow.com/questions/48771614/is-gcc-or-clang-correct-about-this-behavior

For posterity, the part of the spec quoted regarding the behavior is:

basic.scope.pdecl:
    The point of declaration for a name is immediately after its complete
declarator (Clause [dcl.decl]) and before its initializer (if any), except as
noted below. [ Example:

    int x = 12;{ int x = x; }

    Here the second x is initialized with its own (indeterminate) value. — end
example ]

and dcl.fct.default:

Default arguments are evaluated each time the function is called. The order of
evaluation of function arguments is unspecified. Consequently, parameters of a
function shall not be used in a default argument, even if they are not
evaluated. Parameters of a function declared before a default argument are in
scope and can hide namespace and class member names