Re: Is it possible to catch an exception raised by a member variable?

 James Kanze <>
Fri, 28 Sep 2007 22:38:45 -0000
On Sep 28, 11:30 am, "Chris ( Val )" <> wrote:

On Sep 28, 7:03 pm, James Kanze <> wrote:


But you still don't have an object. You can use function try
blocks to remap the exception, or to treat it as a fatal error
(e.g. by calling abort or exit), but you cannot return normally
from the constructor, and the object that was being constructed
will not exist.

I have produced a crude example that will attempt to
prove otherwise:

# include <iostream>
# include <string>
# include <exception>

struct DataSource {
  DataSource( std::string ds )
    if( ds != "" )
        throw "Could not connect to database";

class Base
    DataSource Ds;
    Base( std::string );
    ~Base() { std::cout << "Destructing now...\n"; }
    void Print()
    { std::cout << "I am still alive - Please try again.\n"; }

Base::Base( std::string ds )
try // function-try block
 : Ds( ds ) {}
catch( const char* msg ) {
  std::cout << "Exception Caught: \"" << msg << "\"" << '\n';
  throw std::exception();

int main()
  Base* B;

  try {
   B = new Base( "" );
 catch( const std::exception& e )

This is undefined behavior, since it accesses an uninitialized
pointer. If you get here, the assign in the try block has never
occured (and there is no Base object).

   delete B;

  return 0;

I am interested to hear your, and the groups
thoughts on the validity of such a construct.

Totally invalide.

James Kanze (GABI Software)
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