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Re: [C++ Patch] PR 71737
On Fri, Jan 13, 2017 at 11:42 AM, Paolo Carlini
<paolo.carlini@oracle.com> wrote:
> 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?
The clearing of DECL_ORIGINAL_TYPE is to allow set_underlying_type to
then set it to something more appropriate. That function currently
avoids setting DECL_ORIGINAL_TYPE to error_mark_node, perhaps that
should be changed.
Jason