[Bug c++/25632] [4.0/4.1/4.2 Regression] ICE with const int copied into two different functions

["rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from rakdver at atrey dot karlin dot mff dot cuni dot cz  2006-01-03 23:24 -------
Subject: Re:  [4.0/4.1/4.2 Regression] ICE with const int copied into two
different functions

> ------- Comment #7 from mark at codesourcery dot com  2006-01-03 23:01 -------
> Subject: Re:  [4.0/4.1/4.2 Regression] ICE with const int copied
>  into two different functions
> 
> rakdver at gcc dot gnu dot org wrote:
> > ------- Comment #6 from rakdver at gcc dot gnu dot org  2006-01-03 22:40 -------
> > Patch:
> > 
> > http://gcc.gnu.org/ml/gcc-patches/2006-01/msg00136.html
> 
> This patch is not OK, but it's close.
> 
> We should not call unshare_expr on DECL_INITIAL until after the
> mark_used call, as static data members in templates will not have proper
> initializers until after that point.  Also, there's no need to unshare
> *before* calling fold_non_dependent_expr.
> 
> In fact, there's no need to unshare before the return statement at the
> end of the function.  That will avoid creating trees that will only be
> thrown away later.
> 
> So, why not just do:
> 
> return unshare_expr (decl);
> 
> at the end of the function?

because that causes bootstrap failure --
fold_decl_constant_value does

   tree const_expr = expr;
   do
     {
       expr = fold_non_dependent_expr (const_expr);
       const_expr = integral_constant_value (expr);
     }
   while (expr != const_expr);

and if constant_value_1 (called by integral_constant_value) unshares the
expression unconditionally (not only when it processes DECL_INITIAL),
this loop never ends.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25632