[Bug c++/68939] ICE or wrong code with OpenMP privatization of reference to VLAs

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68939

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |openmp, wrong-code

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Adding openmp keyword, so that it not forgotten by me, but I see various other
issues.
E.g. on the following testcase, with -W -Wall and foo2 ifdefed out I see:
pr68939.C: In function ‘void foo(int)’:
pr68939.C:16:10: warning: ‘<anonymous>’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
       T1 b;
          ^
(and with foo2 not ifdefed out a warning in foo2 only, not in foo, strange),
and the gimple dump shows that the temporaries for the VLA type are only
initialized in the lexical block containing the a variable, but not the other
one:

int bar (void);
void baz (int *, long);
void
foo (int x)
{
  typedef int T1[bar () + x];
  if (x == 6)
    {
      T1 a;
      a[0] = 8;
      a[bar () + 5] = 9;
      baz (a, sizeof (a));
    }
  else if (x == 8)
    {
      T1 b;
      b[0] = 9;
      b[bar () + 7] = 10;
      baz (b, sizeof (b));
    }
}
void
foo2 (int x)
{
  typedef int T1[bar () + x];
  if (x == 6)
    {
      T1 buf;
      T1 &a = buf;
      a[0] = 8;
      a[bar () + 5] = 9;
      baz (a, sizeof (a));
    }
  else if (x == 8)
    {
      T1 buf;
      T1 &b = buf;
      b[0] = 9;
      b[bar () + 7] = 10;
      baz (b, sizeof (b));
    }
}

Bet we need to ensure that for the VLA types and REFERENCE_TYPE to VLAs that
they for typedefs they have corresponding DECL_EXPR with TYPE_DECL already at
the spot where the type is defined, and for the case in #c0, i.e. a decl with
REFERENCE_TYPE to non-typedef VLA type arrange for DECL_EXPR with TYPE_DECL to
that VLA type to come before the DECL_EXPR of the VAR_DECL.
Note the C FE e.g. on foo above (with foo2 containing C++ only code ifdefed
out) emits a DECL_EXPR with TYPE_DECL of T1 and thus it works properly.
Jason, any thoughts on this?