[Bug c++/78896] New: Segmentation fault occurs when use variable initialized using structured binding with capture-by-ref lambda

[duongdominhchau at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78896

            Bug ID: 78896
           Summary: Segmentation fault occurs when use variable
                    initialized using structured binding with
                    capture-by-ref lambda
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: duongdominhchau at hotmail dot com
  Target Milestone: ---

I found a segmentation fault while trying structured binding using GCC 7:

This is the source code which caused the segmentation fault:
int main() {
  int a {10};
  auto [b]{ [&a](){} };
  return b - a;
}

The same code under Clang 4 would raise an error instead of a segmentation
fault.
GCC 7: http://melpon.org/wandbox/permlink/WDd8mSy4dCXj8CSa
Clang 4: http://melpon.org/wandbox/permlink/EQfQxrdTrbNbTw2b

If I change the lambda to capture by value, or never use the variable
initialized using structured binding (the variable `b` in my code), no
segmentation fault occurs.



This is the output of the compiler:
prog.cc: In function 'int main()':
prog.cc:4:10: internal compiler error: Segmentation fault
   return b - a;
          ^
0xb04b0f crash_signal
        /home/heads/gcc/gcc-source/gcc/toplev.c:333
0x88b893 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        /home/heads/gcc/gcc-source/gcc/expr.c:10107
0x895c1a store_expr_with_bounds(tree_node*, rtx_def*, int, bool, bool,
tree_node*)
        /home/heads/gcc/gcc-source/gcc/expr.c:5552
0x89684e expand_assignment(tree_node*, tree_node*, bool)
        /home/heads/gcc/gcc-source/gcc/expr.c:5321
0x7ab45d expand_gimple_stmt_1
        /home/heads/gcc/gcc-source/gcc/cfgexpand.c:3641
0x7ab45d expand_gimple_stmt
        /home/heads/gcc/gcc-source/gcc/cfgexpand.c:3737
0x7aca1f expand_gimple_basic_block
        /home/heads/gcc/gcc-source/gcc/cfgexpand.c:5744
0x7b1be6 execute
        /home/heads/gcc/gcc-source/gcc/cfgexpand.c:6355
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