Object files compiled with `g++ -std=c++1y` won't link - c++

Question

I'm on Linux with g++ 5.3.0.
I thought I'd make myself an object file that, when linked, would initialized global variables Argc and Argv so that the main arguments would be available throughout the process.
Argv.hh:
#pragma once
extern char** Argv;
extern int Argc;
Argv.cc:
char** Argv;
int Argc;
static int set_argv(int argc, char** argv, char** env) { Argc = argc; Argv = argv; return 0; }
/* Put the function into the init_array */
__attribute__((section(".init_array"))) static void *ctr = (void*)&set_argv;
main.cc
#include "Argv.hh"
#include <stdio.h>
int main(){
for (int i = 0; i < Argc; ++i){
puts(Argv[i]);
}
return 0;
}
My original build script was:
com='g++ -std=c++1y'
for cc in *.cc; do $com -c $cc; done
g++ *.o
but it kept giving me a linking error. So I changed com to
gcc -x c -std=c99 and it worked, and it also worked with plain com=g++.
Each of the three compilers successfully compiles, only the linking part fails with g++ -std=c++1y.
nm *.o outputs:
For gcc -x c -std=c99:
Argv.o:
0000000000000004 C Argc
0000000000000008 C Argv
0000000000000000 t ctr
0000000000000000 t set_argv
main.o:
U Argc
U Argv
0000000000000000 T main
U puts
For g++:
Argv.o:
0000000000000008 B Argc
0000000000000000 B Argv
0000000000000000 t _ZL3ctr
0000000000000000 t _ZL8set_argviPPcS0_
main.o:
U Argc
U Argv
0000000000000000 T main
U puts
And for g++ -std=c++1y:
Argv.o:
0000000000000008 B Argc
0000000000000000 B Argv
0000000000000000 t _ZL3ctr
0000000000000000 t _ZL8set_argviPPcS0_
main.o:
0000000000000008 B Argc
0000000000000000 B Argv
0000000000000000 T main
U puts
The last set of object files fails to link with
main.o:(.bss+0x0): multiple definition of `Argv'
Argv.o:(.bss+0x0): first defined here
main.o:(.bss+0x8): multiple definition of `Argc'
Argv.o:(.bss+0x8): first defined here
collect2: error: ld returned 1 exit status
Why does g++ -std=c++1y generate B symbols for extern declarations when the other two generate (as they should?) undefined references? Is this a bug?