Re: [PATCH] c++/114409 - ANNOTATE_EXPR and templates

[Jason Merrill <jason@redhat.com>]

On 4/10/24 13:10, Richard Biener wrote:
> On Wed, 10 Apr 2024, Jakub Jelinek wrote:
> 
>> On Wed, Apr 10, 2024 at 06:43:02PM +0200, Richard Biener wrote:
>>> The following fixes a mismatch in COMPOUND_EXPR handling in
>>> tsubst_expr vs tsubst_stmt where the latter allows a stmt in
>>> operand zero but the former doesn't.  This makes a difference
>>> for the case at hand because when the COMPOUND_EXPR is wrapped
>>> inside an ANNOTATE_EXPR it gets handled by tsubst_expr and when
>>> not, tsubst_stmt successfully handles it and the contained
>>> DECL_EXPR in operand zero.
>>>
>>> The following makes handling of COMPOUND_EXPR in tsubst_expr
>>> consistent with that of tsubst_stmt for the operand that doesn't
>>> specify the result and thus the reason we choose either or the
>>> other for substing.
>>>
>>> Bootstrapped and tested on x86_64-unknown-linux-gnu, OK?
>>>
>>> Thanks,
>>> Richard.
>>>
>>> 	PR c++/114409
>>> gcc/cp/
>>> 	* pt.cc (tsubst_expr): Recurse to COMPOUND_EXPR operand
>>> 	zero using tsubst_stmt, when that returns NULL return
>>> 	the subst operand one, mimicing what tsubst_stmt does.
>>>
>>> gcc/testsuite/
>>> 	* g++.dg/pr114409.C: New testcase.
>>
>> I've posted https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114409#c16
>> for this already and Jason agreed to that version, so I just have to test it
>> tonight:
>> https://gcc.gnu.org/pipermail/gcc-patches/2024-April/649165.html
> 
> Ah, I saw the bugzilla patches and wanted this version to be sent
> because I think the COMPOUND_EXPR inconsistency is odd.  So Jason,
> please still have a look, not necessarily because of the bug
> which can be fixed in multiple ways but because of that COMPOUND_EXPR
> handling oddity (there are already some cases in tsubst_expr that
> explicitly recurse with tsubst_stmt).

The difference between tsubst_stmt and tsubst_expr handling of 
COMPOUND_EXPR seems consistent with the general difference between the 
two functions, so I think this change isn't needed.  The two existing 
uses of tsubst_stmt in tsubst_expr are statement-expressions (for the 
substatement) and transactions (strangely, non-statement transactions 
are handled in tsubst_stmt).

Jason