[Bug c++/85108] [7/8 Regression] Incorrect warning for constexpr lambda with -Wunused-but-set-variable

2018-03-29 Thread rguenth at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85108

Richard Biener  changed:

   What|Removed |Added

   Priority|P3  |P2
   Target Milestone|--- |7.4

[Bug c++/85108] [7/8 Regression] Incorrect warning for constexpr lambda with -Wunused-but-set-variable

2018-03-28 Thread msebor at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85108

Martin Sebor  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
  Known to work||6.4.0
   Keywords||diagnostic
   Last reconfirmed||2018-03-28
 CC||msebor at gcc dot gnu.org
 Ever confirmed|0   |1
Summary|Incorrect warning for   |[7/8 Regression] Incorrect
   |constexpr lambda with   |warning for constexpr
   |-Wunused-but-set-variable   |lambda with
   ||-Wunused-but-set-variable
  Known to fail||7.3.0, 8.0

--- Comment #2 from Martin Sebor  ---
Confirmed.  Bisection points to r239267 (gcc 7.0.0):

r239267 | jason | 2016-08-09 00:33:42 -0400 (Tue, 09 Aug 2016) | 7 lines

Fix empty class parameters with constexpr.

PR c++/67131
* class.c (is_really_empty_class): Call complete_type.
* constexpr.c (cxx_eval_constant_expression): Check
is_really_empty_class.
(potential_constant_expression_1): Likewise.  Check for error type.