[Bug target/39545] New: structures with zero-length array passed/returned inconsistently

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

[hjl@gnu-6 tmp]$ cat f-1.c
struct line {
int length;
char contents[];
};

void foo (struct line);

struct line
bar ()
{
 struct line x;
 x.length = sizeof (struct line);
 foo (x);
 return x;
}
[hjl@gnu-6 tmp]$ /usr/gcc-4.4/bin/gcc -fno-asynchronous-unwind-tables -O2 -S
f-1.c
[hjl@gnu-6 tmp]$ cat f-1.s
        .file   "f-1.c"
        .text
        .p2align 4,,15
.globl bar
        .type   bar, @function
bar:
        pushq   %rbx
        movq    %rdi, %rbx
        subq    $32, %rsp
        movl    $4, (%rdi)
        movl    $4, (%rsp)
        call    foo
        movl    $4, (%rbx)
        movq    %rbx, %rax
        addq    $32, %rsp
        popq    %rbx
        ret
        .size   bar, .-bar
        .ident  "GCC: (GNU) 4.4.0 20090317 (experimental) [trunk revision
144915]"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$ cat f-2.c
struct line {
int length;
struct {} c;
};

void foo (struct line);

struct line
bar ()
{
 struct line x;
 x.length = sizeof (struct line);
 foo (x);
 return x;
}
[hjl@gnu-6 tmp]$ /usr/gcc-4.4/bin/gcc -fno-asynchronous-unwind-tables -O2 -S
f-2.c
[hjl@gnu-6 tmp]$ cat f-2.s
        .file   "f-2.c"
        .text
        .p2align 4,,15
.globl bar
        .type   bar, @function
bar:
        subq    $8, %rsp
        movl    $4, %edi
        call    foo
        movl    $4, %eax
        addq    $8, %rsp
        ret
        .size   bar, .-bar
        .ident  "GCC: (GNU) 4.4.0 20090317 (experimental) [trunk revision
144915]"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$


-- 
           Summary: structures with zero-length array passed/returned
                    inconsistently
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl dot tools at gmail dot com
GCC target triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39545