• Nick Sabalausky (8/8) Jun 02 2011 I found a user comment on an MDSN Windows API reference page (Which I've...
• Andrej Mitrovic (4/4) Jun 02 2011 Maybe they mean UCS-2? I know that for example Charles Petzold's
• Steven Schveighoffer (23/31) Jun 02 2011 Easy enough to test:
• Andrej Mitrovic (1/1) Jun 02 2011 Btw there's .alignof for these things, which will return 2 bytes.

"Nick Sabalausky" <a a.a> writes:

I found a user comment on an MDSN Windows API reference page (Which I've 
since lost, but I think it was somewhere in the Registry section.) that 
claims that the Unicode-taking functions in the Windows API (or at least 
some of them) require the unicode strings to be aligned on a two-byte 
boundary, otherwise they might not work.

Do D's wstrings (in both D1 and D2) always follow this two-byte alignment 
(provided that you're not doing any packed-alignment structs, or 
cast-trickery), or is it something that we need to manually check?

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Maybe they mean UCS-2? I know that for example Charles Petzold's
Programming Windows book assumes that UTF16 characters are *always* 2
bytes wide. So maybe that has something to do with that alignment
requirement.

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Thu, 02 Jun 2011 16:53:12 -0400, Nick Sabalausky <a a.a> wrote:

 I found a user comment on an MDSN Windows API reference page (Which I've
 since lost, but I think it was somewhere in the Registry section.) that
 claims that the Unicode-taking functions in the Windows API (or at least
 some of them) require the unicode strings to be aligned on a two-byte
 boundary, otherwise they might not work.

 Do D's wstrings (in both D1 and D2) always follow this two-byte alignment
 (provided that you're not doing any packed-alignment structs, or
 cast-trickery), or is it something that we need to manually check?

Easy enough to test:

steves steve-laptop:~/testd$ cat testalign.d
struct Foo
{
     ubyte pad;
     wchar wc;
}

pragma(msg, Foo.wc.offsetof.stringof);

struct Foo2
{
     ubyte pad;
     dchar dc;
}

pragma(msg, Foo2.dc.offsetof.stringof);
steves steve-laptop:~/testd$ ~/dmd-2.053/linux/bin32/dmd -c testalign.d
2u
4u

So I'd say it does align to 2-byte boundaries (and dchar to 4-byte).  I  
can't think of a situation where the compiler would break this rule,  
except for manually overridden (as you mentioned).

Note that all dynamic heap allocations are 16-byte aligned.

-Steve

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Btw there's .alignof for these things, which will return 2 bytes.