[Bug c++/70555] New: ICE in expand_expr_real_1 accessing a multi-dimensional VLA via lambda-capture

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70555

            Bug ID: 70555
           Summary: ICE in expand_expr_real_1 accessing a
                    multi-dimensional VLA via lambda-capture
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The following test case derived from g++.dg/cpp1y/vla7.C causes an ICE in
todays's trunk of 6.0 as well as in 5.x and 4.9.3. 

$ cat t.c && /build/gcc-trunk/gcc/xgcc -B /build/gcc-trunk/gcc -S -Wall -Wextra
-Wpedantic -xc++ t.c
int f (int n)
{
  int x[n][n];

  [&x](int i) { 
    x[0][i] = 0;
  }(5);
}

t.c: In function âint f(int)â:
t.c:3:13: warning: ISO C++ forbids variable length array âxâ [-Wvla]
   int x[n][n];
             ^
t.c:3:13: warning: ISO C++ forbids variable length array âxâ [-Wvla]
t.c:8:1: warning: no return statement in function returning non-void
[-Wreturn-type]
 }
 ^
t.c: In lambda function:
t.c:5:15: warning: â<anonymous>â is used uninitialized in this function
[-Wuninitialized]
   [&x](int i) {
               ^
t.c:6:11: warning: â<anonymous>â is used uninitialized in this function
[-Wuninitialized]
     x[0][i] = 0;
     ~~~~~~^
t.c:5:15: internal compiler error: in expand_expr_real_1, at expr.c:9651
   [&x](int i) {
               ^
0x10a80e1f expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        /src/gcc/trunk/gcc/expr.c:9645
0x10a77f2f expand_expr_real(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        /src/gcc/trunk/gcc/expr.c:7962
0x10a56cf7 expand_expr
        /src/gcc/trunk/gcc/expr.h:256
0x10a7939f expand_expr_real_2(separate_ops*, rtx_def*, machine_mode,
expand_modifier)
        /src/gcc/trunk/gcc/expr.c:8181
0x1087a59b expand_gimple_stmt_1
        /src/gcc/trunk/gcc/cfgexpand.c:3654
0x1087a8eb expand_gimple_stmt
        /src/gcc/trunk/gcc/cfgexpand.c:3714
0x1088403f expand_gimple_basic_block
        /src/gcc/trunk/gcc/cfgexpand.c:5720
0x10886267 execute
        /src/gcc/trunk/gcc/cfgexpand.c:6335
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