A question regarding exception specification

[LarryChen]

If a class inherits from another and overrides a virtual function, then the exception-specification for the overridden function must be at least as restrictive. What does it mean? Here is an example,

class B
{
public:
	virtual void foo() throw (int)
	{
	}
};

class D: public B
{
public:
	virtual void foo() throw (double)
	{
	}
};

It compiles fine. In the derived class, virtual function foo throws double and in the base class, foo throws int. So double is supposed to be at least as restrictive? Thanks.

[Paul McKenzie]

If a class inherits from another and overrides a virtual function, then the exception-specification

Not to cut you off, but exception specifications have been deprecated in the new C++ standard.

Here are two links explaining this:

http://herbsutter.com/2010/03/13/tri...dards-meeting/
http://www.gotw.ca/publications/mill22.htm

So are you going to spend time on a "feature" that hardly anyone used, considered broken, and is now deprecated?

Regards,

Paul McKenzie

[LarryChen]

Not to cut you off, but exception specifications have been deprecated in the new C++ standard.

Here are two links explaining this:

http://herbsutter.com/2010/03/13/tri...dards-meeting/
http://www.gotw.ca/publications/mill22.htm

So are you going to spend time on a "feature" that hardly anyone used, considered broken, and is now deprecated?

Regards,

Paul McKenzie

It is good to know. Thanks.

[OReubens]

not to mention that hardly any compiler even actually implemented it, even if they supported the syntax.

but what the old rule basically said...
if your base class implementation throws X and Y then a derived class implementation can be specified to throw
* nothing
* only X
* only Y
* X and Y
it can't throw something else than those, because any code working off the base class only knows of a possible X and Y being thrown. So an overloaded implementation can't be allowed to throw something the base class doesn't specify.

but as stated, this is deprecated, and even in pre C++11 compilers you'd be hard pressed to find a compiler actually fully implementing it.

[LarryChen]

not to mention that hardly any compiler even actually implemented it, even if they supported the syntax.

but what the old rule basically said...
if your base class implementation throws X and Y then a derived class implementation can be specified to throw
* nothing
* only X
* only Y
* X and Y
it can't throw something else than those, because any code working off the base class only knows of a possible X and Y being thrown. So an overloaded implementation can't be allowed to throw something the base class doesn't specify.

but as stated, this is deprecated, and even in pre C++11 compilers you'd be hard pressed to find a compiler actually fully implementing it.

Your explanation is very clear. Thank you very much!