Oct 14 2020

V1067. Throwing from exception constructor may lead to unexpected behavior.

Oct 14 2020

The analyzer has detected an exception constructor that may throw another exception. Using such a class may cause the program to behave unexpectedly when handling exceptions.

Consider the following synthetic example:

#include <stdexcept>

class divide_by_zero_error : public std::invalid_argument
{
public:
  divide_by_zero_error() : std::invalid_argument("divide_by_zero")
  {
    ....
    if (....)
    {
      throw std::runtime_error("oops!");   // <=
    }
  }
};

void example(int a, int b)
{
  try
  {
    if (b == 0)
      throw divide_by_zero_error ();
    ....
  }
  catch (const divide_by_zero_error &e)
  {
    ....
  }

  // my_exception thrown and unhandled
}

In the code of the 'example' function, the programmer intends the raised 'divide_by_zero_error' exception to be handled, but instead of it, an 'std::runtime_error' exception will be thrown, which will not be caught by the subsequent 'catch' block. As a result, the exception will leave the 'example' function, thus causing one of the following situations:

the exception will be handled by another exception handler higher on the call stack, which may also be an undesired behavior;
there could be no appropriate exception handler higher on the call stack, in which case the program will crash by calling the 'std::terminate' function as soon as the exception leaves the 'main' function.

Write and use custom exception classes with particular care because their constructors may throw exceptions at unexpected points – for example, when calling other functions. In the following example, when creating a logging exception, a second exception may be thrown by the 'Log' function:

#include <ios>

static void Log(const std::string& message)
{
  ....
  // std::ios_base::failure may be thrown by stream operations
  throw std::ios_base::failure("log file failure");
}

class my_logging_exception : public std::exception
{
public:
  explicit my_logging_exception(const std::string& message)
  {
    Log(message); // <=
  }
};

This diagnostic rule is classified as: