[Bug libstdc++/48547] iostream and some other C++ libraries do not work with -fpack-struct

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48547

--- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-04-11 07:56:16 UTC ---
(In reply to comment #18)
> 
> it sounds to me from your post that it would be a lot of extra work for the
> compiler builders, making 2 sets of binaries for the cases of -fpack-struct and
> not -fpack-struct.  If this could be accomplished and even have statically
> linked libstdc++ (at least the latter) I think a lot of people would be very
> happy, and for the former, a lot of compiler users would be a lot less
> disgruntled with g++.

I think you overestimate the number of people who care about this issue.

> so... why is -fpack-struct even there?  is it for gcc only and not for g++? 
> because it works fine for ANSI C.  just not any lib with dependent upon
> iostream (like iterator - gaah!).

It works ok for some C++ code, but not if you include the standard library
headers.

> by the way, in the header files of the C++ files where I see the structures
> defined for win32, I *don't* remember ever seeing see #pragma pack().
> but yes, it is in VC++.
> I just put a link to #pragma pack() on my web site for new compiler users.
> I've been writing programs in C for about 20 years and I have not learned about
> this until now.  never heard about it.  nobody talks about it.

It's documented in the manual:
http://gcc.gnu.org/onlinedocs/gcc/Structure_002dPacking-Pragmas.html