[Bug c++/70649] New: [6 Regression] Incorrect C++ warning on zero-sized array passing

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70649

            Bug ID: 70649
           Summary: [6 Regression] Incorrect C++ warning on zero-sized
                    array passing
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: jason at redhat dot com
  Target Milestone: ---

[hjl@gnu-6 pr60336d]$ cat x.i
struct dummy0 { int i; };
struct dummy { struct dummy0 d[0]; };
extern void fun(struct dummy, int);
void
foo (void)
{
  struct dummy d;
  fun(d, 1);
}
[hjl@gnu-6 pr60336d]$ g++ -S -Wabi=9 x.i 
[hjl@gnu-6 pr60336d]$ cat x.s
        .file   "x.i"
        .text
        .globl  _Z3foov
        .type   _Z3foov, @function
_Z3foov:
.LFB0:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    $1, %edi
        call    _Z3fun5dummyi
        nop
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   _Z3foov, .-_Z3foov
        .ident  "GCC: (GNU) 5.3.1 20160406 (Red Hat 5.3.1-6)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-6 pr60336d]$ /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xg++
-B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -S -Wabi=9 x.i 
x.i: In function ‘void foo()’:
x.i:8:12: warning: call to ‘fun’: empty class ‘dummy’ parameter passing ABI
changes in -fabi-version=10 (GCC 6) [-Wabi]
   fun(d, 1);
            ^
[hjl@gnu-6 pr60336d]$ cat x.s
        .file   "x.i"
        .text
        .globl  _Z3foov
        .type   _Z3foov, @function
_Z3foov:
.LFB0:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    $1, %edi
        call    _Z3fun5dummyi
        nop
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   _Z3foov, .-_Z3foov
        .ident  "GCC: (GNU) 6.0.0 20160413 (experimental)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-6 pr60336d]$ 

The warning is incorrect since there is no change in zero-sized array passing.