FALSE NEGATIVE: Division-by-zero checking misses zero from a logical ternary

CHR — Fri, 18 Sep 2026 07:55:51 -0000

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/15052

FALSE NEGATIVE: `zerodiv` misses zero written through an out-parameter

CHR — Fri, 18 Sep 2026 07:43:35 -0000

Example added here: https://trac.cppcheck.net/ticket/14239

FALSE NEGATIVE: zerodiv misses a known zero divisor in a function template with an unknown branch condition

CHR — Fri, 18 Sep 2026 07:40:59 -0000

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/15051

FALSE NEGATIVE: Division-by-zero checking misses a divisor constrained by a switch case

CHR — Fri, 18 Sep 2026 07:29:24 -0000

See https://trac.cppcheck.net/ticket/10

FALSE NEGATIVE: `zerodiv` misses a scalar zeroed by `memset`

CHR — Fri, 18 Sep 2026 06:44:13 -0000

See https://trac.cppcheck.net/ticket/14239

FALSE NEGATIVE: `zerodiv` misses zero assigned by a temporary object's destructor

Rodri — Thu, 17 Sep 2026 17:21:31 -0000

Hi, I found a false negative in Cppcheck 2.21.0 and 2.22 dev when destruction of a temporary object changes a global value to zero before a division.

Affected tool

Cppcheck 2.21.0; also reproduced with Cppcheck 2.22 dev

Affected checker

Cppcheck CheckOther::checkZeroDivision (zerodiv / zerodivcond)

Minimal reproducer

int global;

struct Value {
    Value() { global = 1; }
    ~Value() { global = 0; }
};

int test() {
    Value{};
    return 1 / global;
}

Reproduction command

cppcheck --version
cppcheck --enable=warning --std=c++17 --checkers-report=checkers.txt --template='{file}:{line}:{column}: [{id}] {message}' cppcheck-zerodiv-fn-temporary-destructor.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 line 10 because the temporary's destructor assigns zero to global before the division.

FALSE NEGATIVE: zerodiv misses a known zero divisor in a function template with an unknown branch condition

Rodri — Thu, 17 Sep 2026 17:20:09 -0000

Hi, I found a false negative in Cppcheck 2.21.0 and 2.22 dev when a constant argument makes a division inside a function-template instantiation divide by zero.

Affected tool

Cppcheck 2.21.0; also reproduced with Cppcheck 2.22 dev

Affected checker

Cppcheck CheckOther::checkZeroDivision (zerodiv / zerodivcond)

Minimal reproducer

bool unknown();

template <class T>
void divide(T value) {
  if (unknown())
    value = 1 / (value - 5);
}

void test() {
  divide<int>(5);
}

Reproduction command

cppcheck --version
cppcheck --enable=warning --std=c++17 --checkers-report=checkers.txt --template='{file}:{line}:{column}: [{id}] {message}' cppcheck-zerodiv-fn-template-unknown-branch.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 line 6 because the instantiation receives value == 5, making value - 5 equal to zero.

FALSE NEGATIVE: Division-by-zero checking misses a divisor constrained by a switch case

Rodri — Thu, 17 Sep 2026 17:19:33 -0000

Hi, I found a false negative in Cppcheck 2.21.0 when a switch case constrains the divisor to zero.

Affected tool

Cppcheck 2.21.0

Affected checker

Cppcheck CheckOther::checkZeroDivision (zerodiv / zerodivcond)

Minimal reproducer

int divide_in_zero_case(int value) {
  switch (value) {
  case 0:
    return 1 / value;
  default:
    return 0;
  }
}

Reproduction command

cppcheck --version
cppcheck --enable=warning --std=c11 --checkers-report=checkers.txt --template='{file}:{line}:{column}: [{id}] {message}' cppcheck-zerodiv-fn-switch-case.c

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 4 because the case 0 branch executes the division with value == 0.

FALSE NEGATIVE: `zerodiv` misses zero written through an out-parameter

Rodri — Thu, 17 Sep 2026 17:18:24 -0000

Hi, I found a false negative in Cppcheck 2.21.0 and 2.22 dev when a helper writes zero through a pointer before the pointed-to value is used as a divisor.

Affected tool

Cppcheck 2.21.0; also reproduced with Cppcheck 2.22 dev

Affected checker

Cppcheck CheckOther::checkZeroDivision (zerodiv / zerodivcond)

Minimal reproducer

void set_zero(int *value) {
  *value = 0;
}

int test() {
  int value;
  set_zero(&value);
  return 1 / value;
}

Reproduction command

cppcheck --version
cppcheck --enable=warning --std=c++17 --checkers-report=checkers.txt --template='{file}:{line}:{column}: [{id}] {message}' cppcheck-zerodiv-fn-out-parameter.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 line 8 because set_zero(&value) stores zero in value before the division.

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

Rodri — Thu, 17 Sep 2026 17:17:23 -0000

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.

Recent posts to Discussion

FALSE NEGATIVE: Division-by-zero checking misses zero from a logical ternary

FALSE NEGATIVE: `zerodiv` misses zero written through an out-parameter

FALSE NEGATIVE: zerodiv misses a known zero divisor in a function template with an unknown branch condition

FALSE NEGATIVE: Division-by-zero checking misses a divisor constrained by a switch case

FALSE NEGATIVE: `zerodiv` misses a scalar zeroed by `memset`

FALSE NEGATIVE: `zerodiv` misses zero assigned by a temporary object's destructor

FALSE NEGATIVE: zerodiv misses a known zero divisor in a function template with an unknown branch condition

FALSE NEGATIVE: Division-by-zero checking misses a divisor constrained by a switch case

FALSE NEGATIVE: `zerodiv` misses zero written through an out-parameter

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