[llvm-bugs] [Bug 33442] New: UBSAN: right shift by negative value is not caught for some values

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=33442

            Bug ID: 33442
           Summary: UBSAN: right shift by negative value is not caught for
                    some values
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: babokin at gmail.com
                CC: llvm-bugs at lists.llvm.org

clang trunk
RHS of shift operator is negative, but UBSAN doesn't trigger. Effect is value
sensitive (change to x-1 to see that UBSAN triggers). Computation in the
example do not involve overflow/underflow.

> cat f.cpp
long long int x = -2869500996303312813LL;
int i;
int main() {
  i = 0 >> (x - 280373316);
  return 0;
}

> clang++ -std=c++11 -fsanitize=undefined f.cpp -o out
> ./out

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