[Bug c++/83730] New: Unnecessary generation of guard variables with -fno-threadsafe-statics

[klaus.doldinger64 at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83730

            Bug ID: 83730
           Summary: Unnecessary generation of guard variables with
                    -fno-threadsafe-statics
           Product: gcc
           Version: 7.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: klaus.doldinger64 at googlemail dot com
  Target Milestone: ---

Compiling the following example using -fno-threadsafe-statics and -Os still
generates the guard-variables for the member mTop. This is unnecessary and
occupies 8 Bytes on an avr target.

struct A {
    A() = default; // if commented out, no guards are allocated
    void foo() {}
};

template<typename T>
struct B {
    static void foo() {
        mTop.foo();
    }
    inline static T mTop;
};

int main() {
    B<A>::foo();
}