codeql/cpp/ql/test/query-tests/Likely Bugs/RedundantNullCheckSimple/RedundantNullCheckSimple.cpp

void test_simple_bad(int *p) {
  int x;
  x = *p;
  if (p == nullptr) { // BAD
    return;
  }
}

void test_not_same_basic_block(int *p) {
  int x = *p;
  if (x > 100)
    return;
  if (!p) // BAD
    return;
}

void test_indirect(int **p) {
  int x;
  x = **p;
  if (*p == nullptr) { // BAD
    return;
  }
}

struct ContainsIntPtr {
  int **intPtr;
};

bool check_curslist(ContainsIntPtr *cip) {
  // both the deref and the null check come from the same instruction, but it's
  // an AliasedDefinition instruction.
  return *cip->intPtr != nullptr; // GOOD
}

void test_no_single_dominator(int *p, bool b) {
  int x;
  if (b) {
    x = *p;
  } else {
    x = *p;
  }
  if (p == nullptr) { // BAD [NOT DETECTED]
    return;
  }
}

int test_postdominator_same_bb(int *p) {
  int b = (p == nullptr); // BAD
  // This dereference is a postdominator of the null check, meaning that all
  // paths from the check to the function exit will pass through it.
  return *p + b;
}

int test_postdominator(int *p) {
  int b = (p == nullptr); // BAD [NOT DETECTED]

  if (b) b++; // This line breaks up the basic block

  // This dereference is a postdominator of the null check, meaning that all
  // paths from the check to the function exit will pass through it.
  return *p + b;
}

int test_inverted_logic(int *p) {
  if (p == nullptr) { // BAD [NOT DETECTED]
    // The check above should probably have been `!=` instead of `==`.
    return *p;
  } else {
    return 0;
  }
}

void test_indirect_local() {
  int a = 0;
  int *p = &a;
  int **pp = &p;
  int x;
  x = **pp;
  if (*pp == nullptr) { // BAD
    return;
  }
}

void test_field_local(bool boolvar) {
  int a = 0;
  struct {
    int *p;
  } s = { &a };
  auto sp = &s;

  if (boolvar) {
    int x = *sp->p;
    if (sp->p == nullptr) { // BAD
      return;
    }
  } else {
    int *x = sp->p;
    if (sp == nullptr) { // BAD [NOT DETECTED]
      return;
    }
  }
}

struct S {
  long **pplong;

  void test_phi() {
    while (*pplong != nullptr) { // GOOD
      pplong++;
    }
  }
};