------- Comment #28 from rguenther at suse dot de 2009-04-09 07:58 -------
Subject: Re: C++ empty struct is passed incorrectly
On Wed, 8 Apr 2009, hjl dot tools at gmail dot com wrote:
> ------- Comment #23 from hjl dot tools at gmail dot com 2009-04-08 23:41
> -------
> This looks like an ABI issue:
>
> [...@gnu-6 pr39678]$ cat pr39678.c
> #include <stdio.h>
>
> struct Y {};
> struct X {
> struct Y y;
> __complex__ float val;
> };
>
> struct X __attribute__((noinline))
> foo (float *p)
> {
> struct X x;
> __real x.val = p[0];
> __imag x.val = p[1];
> return x;
> }
> #ifdef __cplusplus
> extern "C"
> #endif
> void abort (void);
> float a[2] = { 3., -2. };
> int main()
> {
> struct X x = foo(a);
> printf ("X: %d\n", (int) sizeof (struct X));
> printf ("Y: %d\n", (int) sizeof (struct Y));
> if (__real x.val != 3.)
> abort ();
> if (__imag x.val != -2.)
> abort ();
> return 0;
> }
> [...@gnu-6 pr39678]$ gcc pr39678.c
> [...@gnu-6 pr39678]$ ./a.out
> X: 8
> Y: 0
> [...@gnu-6 pr39678]$ g++ pr39678.c
> [...@gnu-6 pr39678]$ ./a.out
> X: 12
> Y: 1
> Aborted
> [...@gnu-6 pr39678]$
>
> "struct Y {};" isn't handled properly in C++.
sizeof(Y) is 1 according to the C++ standard.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39678
