Re: gcc pragma pack on hpux

[Eric Frias <efrias at syncad dot com>]

John David Anglin wrote:
[regarding enabling #pragma pack on HP-UX, which for some reason is
 disabled in gcc]
> The maximum alignment available for bss/common variables is 8 bytes
> with the 32-bit SOM linker.  That's the only restriction that I'm
> aware of,  Thus, it may be ok to define HANDLE_PRAGMA_PACK_PUSH_POP
> in the file hpux.h.

I've just tried running the GCC test suite (make check-gcc), and it
looks good.  I did three tests: first with the gcc-3.4.2 distribution,
next with HANDLE_PRAGMA_PACK_PUSH_POP in pa/pa-hpux.h, and finally
defining HANDLE_PRAGMA_PACK defined instead.  The results of all three
tests were identical:

                === gcc Summary ===
# of expected passes            24024
# of expected failures          69
# of unresolved testcases       22
# of untested testcases         7
# of unsupported tests          373
/devel/syncad/build-gcc-3.4.2/gcc/xgcc version 3.4.2

I don't know how you choose which version of #pragma pack should be
enabled for this platform.  If the choice is based on what the native
compilers do, it looks like the non-push-pop version is closer to the
desired behavior.  The native HP compiler's pragma pack is documented here:
	http://docs.hp.com/en/8/pragmas.htm#pragma-pack

I'd like to make one of these #pragma pack options enabled by default on 
HP-UX, unless there's a good reason why it should remain disabled. 
Enabling it would make my life a lot easier and my source code a lot 
cleaner (I'm not the only one, google turns up a two or three other 
discussions where people had to work around the lack of #pragma pack on 
hp).  If this is possible, what can I do to help make it happen?

Thanks,

Eric

John David Anglin wrote:
> > I have a question about the HP-UX port of gcc, and from looking at the
> > gcc Contributors list it looks like you're the person to ask.  I'm
> > working on porting some software (winelib) that makes heavy use of
> > #pragma pack, and gcc doesn't support this pragma on HP-UX.  I was
> > hoping you could tell me why it is disabled.
> >
> > I tried adding the HANDLE_PRAGMA_PACK define to gcc's config files and
> > it looks like #pragma pack started working correctly (I haven't run the
> > regression tests yet to confirm it).
>
>
> I don't know.  It hasn't come up in the period that I have been
> involved in GCC.
>
>
> > If necessary, I think I can use __attribute__((packed,aligned(x))) to
> > work around this, but it needs to be applied on a structure-by-structure
> > basis.  The software I'm porting has about 10k lines surrounded by
> > pragma pack directives, so converting it to use attributes would be very
> > tedious.
> >
> > Do you know if turning on these options will break anything?  Is there
> > any chance future releases of gcc will have this enabled by default?