Re: [C++ Patch] PR 71737

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

On 13/01/2017 15:51, Nathan Sidwell wrote:
> On 01/13/2017 09:45 AM, Paolo Carlini wrote:
> > Hi,
> >
> > in this error recovery issue get_underlying_template crashes when
> > TYPE_TEMPLATE_INFO_MAYBE_ALIAS is applied to a null orig_type. Simply
> > checking for that condition appears to solve the issue in a
> > straightforward way. Tested x86_64-linux.
>
> Wouldn't it be better if a scrogged alias got error_mark_node as the 
> underlying type?  (I have no idea whether that's an easy thing to 
> accomplish)
Your reply, Nathan, led me to investigate where exactly 
DECL_ORIGINAL_TYPE becomes null, and turns out that in tsubst_decl we 
have code actively doing that. That same code, a few lines below, only 
sets TYPE_DEPENDENT_P_VALID to false if type != error_mark_node. I 
cannot say to fully understand yet all the details, but certainly the 
patchlet below also passes testing. Do you have comments about this too?

Thanks!
Paolo.

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