[Bug c/67469] New: "-pie -fpie" result in BSS instead of undefined symbols

["nyh at math dot technion.ac.il" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67469

            Bug ID: 67469
           Summary: "-pie -fpie" result in BSS instead of undefined
                    symbols
           Product: gcc
           Version: 5.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nyh at math dot technion.ac.il
  Target Milestone: ---

I've noticed a really strange phenomenon in Gcc 5.1.1 compared to Gcc 4.9.2. I
don't know if it's a bug or a feature.

Consider the following simple C program:
    #include <stdio.h>
    int main(){
        printf("%p\n", stdout);
    }

I would expect, the compiled dynamic executable should have the symbol "stdout"
as an undefined ("U" in nm) symbol, because it is an external symbol which must
be defined by the shared library.

But, if I compile it on gcc 5.1.1 with the command:

   cc -pie -fpie file.c

and do "nm -D a.out", I see that stdout is in the BSS ("B") instead of being
undefined ("U")!

Strangely, if I use -fpic instead of -fpie, i.e. "cc -pie -fpic" - this issue 
does not appear and I get "U" as I expected. I also get "U" when compiling with
"-shared -fpic". In gcc 4.9.2 I got "U" in all these cases.

However, one reason I'm not sure this is actually a bug is that when I compile
without any pic/pie parameters (i.e., a normal non-relocatable executable), I
get the "B" symbol as well - and this also used to be the case in 4.9.2. So
maybe this was always the intended behavior, but I just don't understand why?