[Bug c++/84608] New: Hang in cxx_eval_constant_expression() with -fsanitize=undefined

[vegard.nossum at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84608

            Bug ID: 84608
           Summary: Hang in cxx_eval_constant_expression() with
                    -fsanitize=undefined
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vegard.nossum at gmail dot com
  Target Milestone: ---

Created attachment 43525
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43525&action=edit
GDB stack trace

Input:

void f(void) {
        return { 00 + 0 << 101 >> 2 + 0 >> 0 >> ~010 + 0 << 0 >> ~~00 << 1 <<
~~0 + ~010 + 0 << 0 << 0 + 0 + 0 >> 0 + ~0 << ~0 + 22 + 2120 + ~0 >> 200 << 01
>> 10 << ~0 + 0 >> 0 << 0 >> 210 >> 0 << ~100 + 0 >> 0 << 1021 + 10 >> 02 >> 0
>> 2 + 20 };
}

Output:

$ xgcc -x c++ -fsanitize=undefined -c -
<stdin>: In function 'void f()':
<stdin>:2:21: warning: left shift count >= width of type
[-Wshift-count-overflow]
<stdin>:2:49: warning: right shift count is negative [-Wshift-count-negative]
<stdin>:2:85: warning: left shift count is negative [-Wshift-count-negative]
<stdin>:2:113: warning: right shift count is negative [-Wshift-count-negative]
<stdin>:2:136: warning: left shift count >= width of type
[-Wshift-count-overflow]
<stdin>:2:141: warning: right shift count >= width of type
[-Wshift-count-overflow]
<stdin>:2:165: warning: left shift count is negative [-Wshift-count-negative]
<stdin>:2:180: warning: right shift count >= width of type
[-Wshift-count-overflow]
[hang]

Version:

xgcc (GCC) 8.0.1 20180204 (experimental)

built from git fdae6180ad24fa6303fa046114f3e4b66b8db34d

It seems to have been introduced somewhere between 5.5.0 and 6.1.0.

Please see attachment for gdb stack trace.