[Bug tree-optimization/69253] New: g++ ICE (segfault) at -O0 on x86_64-linux-gnu in "cxx_incomplete_type_diagnostic"

["helloqirun at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69253

            Bug ID: 69253
           Summary: g++ ICE (segfault) at -O0 on x86_64-linux-gnu in
                    "cxx_incomplete_type_diagnostic"
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: helloqirun at gmail dot com
  Target Milestone: ---

The following code causes an ICE when compiled with the current g++ trunk at
-O0  on x86_64-linux-gnu in both 32-bit and 64-bit modes.

Please note that g++ with -O1 and above compiles the code snippet. Should g++
allow the initialization of flexible array members?




$ g++-trunk -v
Using built-in specs.
COLLECT_GCC=g++-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20160112 (experimental) [trunk revision 232269] (GCC)



$ g++-trunk  -O0 -c abc.cc
abc.cc: In function 'void fn1()':
abc.cc:5:33: internal compiler error: in cxx_incomplete_type_diagnostic, at
cp/typeck2.c:567
 void fn1() { (struct str){1, ""}; }
                                 ^

0x6c53cf cxx_incomplete_type_diagnostic(tree_node const*, tree_node const*,
diagnostic_t)
        ../../gcc/gcc/cp/typeck2.c:567
0xf863fa size_in_bytes(tree_node const*)
        ../../gcc/gcc/tree.c:2925
0xa1369c int_expr_size
        ../../gcc/gcc/expr.c:11639
0xa2709a store_expr_with_bounds(tree_node*, rtx_def*, int, bool, bool,
tree_node*)
        ../../gcc/gcc/expr.c:5360
0xa28821 expand_assignment(tree_node*, tree_node*, bool)
        ../../gcc/gcc/expr.c:5021
0x91a9be expand_gimple_stmt_1
        ../../gcc/gcc/cfgexpand.c:3606
0x91a9be expand_gimple_stmt
        ../../gcc/gcc/cfgexpand.c:3702
0x91e0a4 expand_gimple_basic_block
        ../../gcc/gcc/cfgexpand.c:5708
0x923076 execute
        ../../gcc/gcc/cfgexpand.c:6323
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.


------------------
$ cat abc.cc
struct str {
  int a;
  char s[];
};
void fn1() { (struct str){1, ""}; }