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If an error has occured during the memory allocation.How to handle this in constructor?

Assuming you have a standard compliant compiler then if an exception is thrown during construction of an object all fully constructed members and bases (called sub-objects) will have their destructors called. All sub-objects for which construction has not yet completed will not have their destructors called (see the ANSI/ISO C++ Standard section 15.2).

This takes care of cleaning up most if not all cases where construction fails due to errors in the construction of a base class or a class member.

Now to catch and handle the exception in the constructor you may need to use special try - catch syntax that extends around the whole constructor to catch exceptions thrown in the initialiser list, here is an example from the standard with a few additional comments added by myself (see section 15 paragraph 3 of the standard):

       int f(int); // f() may throw

       class C
         int i;
         double d;
         C(int ii, double id);

       C::C(int ii, double id)
       : i( f(ii) ) // i initialised via call to f(), which may throw
       , d( id )
       // constructor function body
       catch (...)
       // handles exceptions thrown from the constructor-initialiser
       // and from the constructor function body

Hope this helps.


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Ralph McArdell


I am a software developer with more than 15 years C++ experience and over 25 years experience developing a wide variety of applications for Windows NT/2000/XP, UNIX, Linux and other platforms. I can help with basic to advanced C++, C (although I do not write just-C much if at all these days so maybe ask in the C section about purely C matters), software development and many platform specific and system development problems.


My career started in the mid 1980s working as a batch process operator for the now defunct Inner London Education Authority, working on Prime mini computers. I then moved into the role of Programmer / Analyst, also on the Primes, then into technical support and finally into the micro computing section, using a variety of 16 and 8 bit machines. Following the demise of the ILEA I worked for a small company, now gone, called Hodos. I worked on a part task train simulator using C and the Intel DVI (Digital Video Interactive) - the hardware based predecessor to Indeo. Other projects included a CGI based train simulator (different goals to the first), and various other projects in C and Visual Basic (er, version 1 that is). When Hodos went into receivership I went freelance and finally managed to start working in C++. I initially had contracts working on train simulators (surprise) and multimedia - I worked on many of the Dorling Kindersley CD-ROM titles and wrote the screensaver games for the Wallace and Gromit Cracking Animator CD. My more recent contracts have been more traditionally IT based, working predominately in C++ on MS Windows NT, 2000. XP, Linux and UN*X. These projects have had wide ranging additional skill sets including system analysis and design, databases and SQL in various guises, C#, client server and remoting, cross porting applications between platforms and various client development processes. I have an interest in the development of the C++ core language and libraries and try to keep up with at least some of the papers on the ISO C++ Standard Committee site at


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