Re: [C++] fix a latent bug in cp-tree.h

[Geoffrey Keating <geoffk at apple dot com>]

On 27/05/2004, at 5:29 AM, Steven Bosscher wrote:

> Hi,
>
> While working on switch lowering for trees, I got a bootstrap error 
> because
> in one of the c++ gt headers, a switch label was out of range of the 
> switch's
> controlling expression.  This turned out to be a switch with three 
> case labels
> on a single-bit bitfield, is_lang_type_class in struct 
> lang_type_header.
> The attached patch should fix that.  Is it safe to use GTY((skip(""))) 
> in a
> union like this?  Bootstapping/testing on amd64 seems to think so, but
> I'd like to be sure and hear from the experts :)

Yes, I think this is OK.  You can check by looking at the generated 
file, which will be gtype-cp.h I think.

> Index: cp/cp-tree.h
> ===================================================================
> RCS file: /cvs/gcc/gcc/gcc/cp/cp-tree.h,v
> retrieving revision 1.968
> diff -c -3 -p -r1.968 cp-tree.h
> *** cp/cp-tree.h        20 May 2004 11:36:14 -0000      1.968
> --- cp/cp-tree.h        27 May 2004 12:20:51 -0000
> *************** struct lang_type GTY(())
> *** 1091,1097 ****
>   {
>     union lang_type_u
>     {
> !     struct lang_type_header GTY((tag ("2"))) h;
>       struct lang_type_class  GTY((tag ("1"))) c;
>       struct lang_type_ptrmem GTY((tag ("0"))) ptrmem;
>     } GTY((desc ("%h.h.is_lang_type_class"))) u;
> --- 1091,1097 ----
>   {
>     union lang_type_u
>     {
> !     struct lang_type_header GTY((skip (""))) h;
>       struct lang_type_class  GTY((tag ("1"))) c;
>       struct lang_type_ptrmem GTY((tag ("0"))) ptrmem;
>     } GTY((desc ("%h.h.is_lang_type_class"))) u;
--
Geoff Keating <geoffk@apple.com>

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