[Bug c++/70594] New: [6 Regression] -fcompare-debug failure

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70594

            Bug ID: 70594
           Summary: [6 Regression] -fcompare-debug failure
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org
                CC: ppalka at gcc dot gnu.org
  Target Milestone: ---

No example as I failed to reduce one; I also tried to use a reduced set of
flags; this set worked on the original file - but not on the delta-reduced
file. All of those point to a memory-related issue. Interestingly, with
-save-temps it didn't occur while w/o -save-temps, the result differed as
follows (two lines shifted down by five lines):

--- /tmp/ccRrTlry.gkd   2016-04-08 09:12:27.463899521 +0200
+++ /tmp/ccV2i7s5.gk.gkd        2016-04-08 09:12:35.739842097 +0200
@@ -74901,2 +74900,0 @@
-29:   void yyreduce = <<< error >>>;
-1861:   void yyerrlab = <<< error >>>;
@@ -74906,0 +74905,2 @@
+29:   void yyreduce = <<< error >>>;
+1861:   void yyerrlab = <<< error >>>;


Bisecting GCC points to Patrick Palka's commit r234753:

    Fix PR c++/70452 (regression in C++ parsing performance)

    gcc/cp/ChangeLog:

        PR c++/70452
        * constexpr.c (struct fundef_copy): New struct.
        (struct fundef_copies_table_t): New struct.
        (fundef_copies_table): New static variable.
        (maybe_initialize_fundef_copies_table): New static function.
        (get_fundef_copy): New static function.
        (save_fundef_copy): New static function.
        (cxx_eval_call_expression): Use get_fundef_copy, and
        save_fundef_copy.
        (constexpr_call_table): Add "deletable" GTY marker.

    gcc/testsuite/ChangeLog:

        PR c++/70452
        * g++.dg/ext/constexpr-vla4.C: New test.