Is it okay to manually throw an std::bad_alloc?

Question

I have this code..

 CEngineLayer::CEngineLayer(void)  {     // Incoming creation of layers. Wrapping all of this in a try/catch block is     // not helpful if logging of errors will happen.      logger = new (std::nothrow) CLogger(this);      if(logger == 0)     {      std::bad_alloc exception;      throw exception;     }      videoLayer = new (std::nothrow) CVideoLayer(this);      if(videoLayer == 0)     {      logger->log("Unable to create the video layer!");       std::bad_alloc exception;      throw exception;     }  }   IEngineLayer* createEngineLayer(void)  {     // Using std::nothrow would be a bad idea here as catching things thrown     // from the constructor is needed.      try     {      CEngineLayer* newLayer = new CEngineLayer;       return (IEngineLayer*)newLayer;     }     catch(std::bad_alloc& exception)     {      // Couldn't allocate enough memory for the engine layer.      return 0;     }  } 

I've omitted most of the non-related information, but I think the picture is clear here.

Is it okay to manually throw an std::bad_alloc instead of try/catching all of the layer creations individually and logging before rethrowing bad_allocs?

Answer 1

Just to answer the question (since nobody else seems to have answered it), the C++03 standard defines std::bad_alloc as follows:

namespace std {   class bad_alloc : public exception {   public:     bad_alloc() throw();     bad_alloc(const bad_alloc&) throw();     bad_alloc& operator=(const bad_alloc&) throw();     virtual ˜bad_alloc() throw();     virtual const char* what() const throw();   }; } 

Since the standard defines a public constructor, you'd be perfectly safe to construct and throw one from your code. (Any object with a public copy constructor can be thrown, IIRC).

Answer 2

You don't need to do that. You can use the parameterless form of the throw statement to catch the std::bad_alloc exception, log it, then rethrow it:

logger = new CLogger(this); try {     videoLayer = new CVideoLayer(this); } catch (std::bad_alloc&) {     logger->log("Not enough memory to create the video layer.");     throw; } 

Or, if logger is not a smart pointer (which it should be):

logger = new CLogger(this); try {     videoLayer = new CVideoLayer(this); } catch (std::bad_alloc&) {     logger->log("Not enough memory to create the video layer.");     delete logger;     throw; } catch (...) {     delete logger;     throw; }