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Incorrect allocation-error handling

ID: cpp/incorrect-allocation-error-handling
Kind: problem
Security severity: 7.5
Severity: warning
Precision: medium
Tags:
   - correctness
   - security
   - external/cwe/cwe-570
   - external/cwe/cwe-252
   - external/cwe/cwe-755
Query suites:
   - cpp-security-extended.qls
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

Different overloads of the new operator handle allocation failures in different ways. If new T fails for some type T, it throws a std::bad_alloc exception, but new(std::nothrow) T returns a null pointer. If the programmer does not use the corresponding method of error handling, allocation failure may go unhandled and could cause the program to behave in unexpected ways.

Recommendation

Make sure that exceptions are handled appropriately if new T is used. On the other hand, make sure to handle the possibility of null pointers if new(std::nothrow) T is used.

Example

// BAD: the allocation will throw an unhandled exception
// instead of returning a null pointer.
void bad1(std::size_t length) noexcept {
  int* dest = new int[length];
  if(!dest) {
    return;
  }
  std::memset(dest, 0, length);
  // ...
}

// BAD: the allocation won't throw an exception, but
// instead return a null pointer.
void bad2(std::size_t length) noexcept {
  try {
    int* dest = new(std::nothrow) int[length];
    std::memset(dest, 0, length);
    // ...
  } catch(std::bad_alloc&) {
    // ...
  }
}

// GOOD: the allocation failure is handled appropriately.
void good1(std::size_t length) noexcept {
  try {
    int* dest = new int[length];
    std::memset(dest, 0, length);
    // ...
  } catch(std::bad_alloc&) {
    // ...
  }
}

// GOOD: the allocation failure is handled appropriately.
void good2(std::size_t length) noexcept {
  int* dest = new(std::nothrow) int[length];
  if(!dest) {
    return;
  }
  std::memset(dest, 0, length);
  // ...
}

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