std::any with small object optimization and safe numerical conversion

The purpose of this tiny header-only library is to provide a type called SafeAny::Any which can hold any type, just like std::any or boost::any. But it has few importants features:

• It has small object optimization for objects smaller than two words (16 bytes on a 64bits platform), thanks to this 3rdparty implementation thelink2012/any.

• it is less pedantic than usual when an arithmetic value (integer, floating point, enum, etc.) is casted into another one. The library will check for narrowing, signedness conversions and numerical cancellation.

Example

using SafeAny::Any;

{
  Any val( int(-1000) );

  int    int_val = val.cast<int>(); //OK
  double real_val = val.cast<double>(); //OK
  double long_val = val.cast<long>(); //OK

  int8_t small_val      = val.cast<uint8_t>(); // throws exception
  uint16_t unsigned_val = val.cast<uint16_t>(); // throws exception
}

{
  Any val( float(3.1) );

  float  f_val = val.cast<float>(); //OK
  double d_val = val.cast<double>(); //OK
  
  int i_val = val.cast<int>(); // throws exception. 
}

Implementation

SafeAny extends std::any with few ideas from Poco::DynamicAny.

The main drawback of Poco::DynamicAny is that it requires heap allocation, something that is slow and not very cache-friendly.