FALSE NEGATIVE: Division-by-zero checking misses a zero sum after two constraints

[Rodri]

Hi, I found a false negative in Cppcheck 2.21.0 when two branch constraints establish that an expression used as a divisor is zero.

Affected tool

Cppcheck 2.21.0

Affected checker

Cppcheck CheckOther::checkZeroDivision (zerodiv / zerodivcond)

Minimal reproducer

int divide_after_two_constraints(int x, int y) {
  if (y != 0)
    return 0;
  if (x + y != 0)
    return 0;
  return y / (x + y);
}

Reproduction command

cppcheck --version
cppcheck --enable=warning --std=c++11 --checkers-report=checkers.txt --template='{file}:{line}:{column}: [{id}] {message}' cppcheck-zerodiv-fn-multiple-constraints.cpp

Current behavior

Cppcheck produces neither a zerodiv nor a zerodivcond diagnostic. The checker report lists CheckOther::checkZeroDivision as active.

Expected behavior

Cppcheck should report a division-by-zero diagnostic at line 6 because reaching that statement establishes x + y == 0.

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/15061