Re: [PATCH] Fix PR 101515 (ICE in pp_cxx_unqualified_id, at cp/cxx-pretty-print.c:128)

[Qing Zhao <qing.zhao@oracle.com>]

> On Feb 9, 2022, at 12:23 PM, Jason Merrill <jason@redhat.com> wrote:
> 
> On 2/9/22 10:51, Qing Zhao wrote:
>>> On Feb 8, 2022, at 4:20 PM, Jason Merrill <jason@redhat.com> wrote:
>>> 
>>> On 2/8/22 15:11, Qing Zhao wrote:
>>>> Hi,
>>>> This is the patch to fix PR101515 (ICE in pp_cxx_unqualified_id, at  cp/cxx-pretty-print.c:128)
>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101515
>>>> It's possible that the TYPE_NAME of a record_type is NULL, therefore when
>>>> printing the TYPE_NAME, we should check and handle this special case.
>>>> Please see the comment of pr101515 for more details.
>>>> The fix is very simple, just check and special handle cases when TYPE_NAME is NULL.
>>>> Bootstrapped and regression tested on both x86 and aarch64, no issues.
>>>> Okay for commit?
>>>> Thanks.
>>>> Qing
>>>> =====================================
>>>> From f37ee8d21b80cb77d8108cb97a487c84c530545b Mon Sep 17 00:00:00 2001
>>>> From: Qing Zhao <qing.zhao@oracle.com>
>>>> Date: Tue, 8 Feb 2022 16:10:37 +0000
>>>> Subject: [PATCH] Fix PR 101515 ICE in pp_cxx_unqualified_id, at
>>>>  cp/cxx-pretty-print.c:128.
>>>> It's possible that the TYPE_NAME of a record_type is NULL, therefore when
>>>> printing the TYPE_NAME, we should check and handle this special case.
>>>> gcc/cp/ChangeLog:
>>>> 	* cxx-pretty-print.cc (pp_cxx_unqualified_id): Check and handle
>>>> 	the case when TYPE_NAME is NULL.
>>>> gcc/testsuite/ChangeLog:
>>>> 	* g++.dg/pr101515.C: New test.
>>>> ---
>>>>  gcc/cp/cxx-pretty-print.cc      |  5 ++++-
>>>>  gcc/testsuite/g++.dg/pr101515.C | 25 +++++++++++++++++++++++++
>>>>  2 files changed, 29 insertions(+), 1 deletion(-)
>>>>  create mode 100644 gcc/testsuite/g++.dg/pr101515.C
>>>> diff --git a/gcc/cp/cxx-pretty-print.cc b/gcc/cp/cxx-pretty-print.cc
>>>> index 4f9a090e520d..744ed0add5ba 100644
>>>> --- a/gcc/cp/cxx-pretty-print.cc
>>>> +++ b/gcc/cp/cxx-pretty-print.cc
>>>> @@ -171,7 +171,10 @@ pp_cxx_unqualified_id (cxx_pretty_printer *pp, tree t)
>>>>      case ENUMERAL_TYPE:
>>>>      case TYPENAME_TYPE:
>>>>      case UNBOUND_CLASS_TEMPLATE:
>>>> -      pp_cxx_unqualified_id (pp, TYPE_NAME (t));
>>>> +      if (TYPE_NAME (t))
>>>> +	pp_cxx_unqualified_id (pp, TYPE_NAME (t));
>>>> +      else
>>>> +	pp_string (pp, "<unnamed type>");
>>> 
>>> Hmm, but it's not an unnamed class, it's a pointer to member function type, and it would be better to avoid dumping compiler internal representations like the __pfn field name.
>> Yes, It’s not an unnamed class, but the ICE happened when try to print the compiler generated member function type “__ptrmemfunc_type”, whose TYPE_NAME is NULLed during building this type in c++ FE and the c++ FE does not handle the case when TYPE_NAME is NULL correctly.
>> So, there are two levels of issues:
>> 1. The first level issue is that the current C++ FE does not handle the case TYPE_NAME being NULL correctly, this is indeed a bug in the current code and should be fixed as in the current patch.
> 
> Sure, we might as well make this code more robust.  But we can do better than <unnamed type> if we check TYPE_PTRMEMFUNC_P.
Okay, so what should we print to the user if it's “TYPE_PTRMEMFUNC_P”? Print nothing or some special string? 
> 
>> 2. The second level issue is what you suggested in the above, shall we print the “compiler generated internal type”  to the user? And I agree with you that it might not be a good idea to print such compiler internal names to the user.  Are we do this right now in general? (i.e, check whether the current TYPE is a source level TYPE or a compiler internal TYPE, and then only print out the name of TYPE for the source level TYPE?) and is there a bit in the TYPE to distinguish whether a TYPE is user -level type or a compiler generated internal type?
> 
>>> I think the real problem comes sooner, when c_fold_indirect_ref_for_warn turns a MEM_REF with RECORD_TYPE into a COMPONENT_REF with POINTER_TYPE.
> 
>> What’s the major issue for this transformation? (I will study this in more details).
> 
> We told c_fold_indirect_ref that we want a RECORD_TYPE (the PMF as a whole) and it gave us back a POINTER_TYPE instead (the __pmf member). Folding shouldn't change the type of an expression like that.

Yes, this is not correct transformation, will study in more detail and try to fix it.

Qing
> 
> Jason