Alignment testing

[Dmitry Timoshkov]

"Hans Leidekker" <hans at it.vu.nl> wrote:

> [Use a fixed width font to view this message]
> 
>                           MSVC   MinGW  GCC
> 
> Alignment of __int64:     8      8      8
> Size of __int64:          8      8      8
> 
> Alignment of large_int:   8      8      4
> Size of large_int:        8      8      8
> 
> Alignment of container1:  8      8      4
> Size of container1:       16     16     12
> 
> Alignment of container2:  8      8      4
> Size of container2:       16     16     12
> 
> Alignment of container3:  8      8      4
> Size of container3:       8      8      8
> 
> Clearly GCC is the odd one out. When a double is embedded in
> a structure GCC does not adjust the alignment of the structure
> to the size of a double.
> 
> So, should we add -malign-double to the compiler flags?

After another inspection of Wine's dlls/kernel/tests/generated.c
I think that MSVC case was actually never tested!

Here is an example of the code:

#if defined(_MSC_VER) && (_MSC_VER >= 1300) && defined(__cplusplus)
# define FIELD_ALIGNMENT(type, field) __alignof(((type*)0)->field)
#elif defined(__GNUC__)
# define FIELD_ALIGNMENT(type, field) __alignof__(((type*)0)->field)
#else
/* FIXME: Not sure if is possible to do without compiler extension */
#endif

I don't know what version of MS cl.exe has _MSC_VER >= 1300, but one
that comes with Visual Studio 6.0 has _MSC_VER set to 1200. Moreover,
since the test is a .c file __cplusplus is never defined, therefore
FIELD_ALIGNMENT is not defined by the above code and later in that
file we have:

#ifdef FIELD_ALIGNMENT
# define TEST_FIELD_ALIGNMENT(type, field, align) \
   ok(FIELD_ALIGNMENT(type, field) == align, \
       "FIELD_ALIGNMENT(" #type ", " #field ") == %d (expected " #align ")\n", \
           FIELD_ALIGNMENT(type, field))
#else
# define TEST_FIELD_ALIGNMENT(type, field, align) do { } while (0)
#endif

i.e. FIELD_ALIGNMENT gets an empty definition. Same for _TYPE_ALIGNMENT.

Patrik, did you actually got it working with MS cl.exe?

-- 
Dmitry.