But you never ever want to catch anything by value (slicing) - assuming C++ of course. You always want to throw by value and catch by reference, or else bad things may happen.
Inline try/catch
You already have stack space for that. of course assuming the exception do not allocate extra memory in copy ctor...
Note that throwing an exception from a destructor is also super bad mojo in C++. Basically any exception guarantees go out the window if you have destructors that throw. It's sufficiently bad that C++11 gave all destructors an implicit noexcept exception specification, meaning that an exception from a destructor will immediately call terminate() unless you specifically enable exceptions for the destructor for the class or one of the subobjects of that class contains a destructor which has exception enabled destructors.
You still don't want to catch by value though, since the object will be sliced if it is a derived class and you catch the base class.
See: http://stackoverflow.com/questions/2522299/c-catch-blocks-catch-exception-by-value-or-reference
Note that throwing an exception from a destructor is also super bad mojo in C++. Basically any exception guarantees go out the window if you have destructors that throw. It's sufficiently bad that C++11 gave all destructors an implicit noexcept exception specification, meaning that an exception from a destructor will immediately call terminate() unless you specifically enable exceptions for the destructor for the class or one of the subobjects of that class contains a destructor which has exception enabled destructors.
Actually I find this one of the more valuable additions to C++11, because if your destructor throws, something is seriously fucked up. At least, usually... there may be singular cases where it may be allowable and desirable, but I must admit I don't see them. I do see the problems, though.
Either you have a "conditional destructor" with some (hopefully bulletproof) logic that prevents it from throwing while being unwound, then your class behaves differently although the expectation would be that it works the same. You now need a separate way of detecting the error condition, or you must simply ignore the error. Either way, this stinks.
Or, you are unaware of what happens when you throw from a destructor during unwind, and do it anyway. This is even worse, in two respects (first, because you don't know the implications, and second because it actually happens, and the program is now in an undefined, unrecoverable state). And, what's worst, now you don't even know what happened, or where.
So, for that this case, crashing hard by terminating the program is a good thing. It forces the programmer to address the issue. Actually, the mere presence of the throw keyword inside a destructor should preferrably generate a build error, if you ask me.
One problem I see with inlineing try catch like that is that it makes it too easy to use. Throwing and catching an exception is an expensive operation, and it's good when the code reflects that complexity. You don't want to encourage non exceptional cases to throw exceptions for the sake of convenient syntax.
Ruby allows this with a simpler syntax.
'Normal' exception handling:
begin
10 / 0
rescue
puts "Please do not divide by zero."
ensure #the 'ensure' section will always execute when the block exits, regardless of exceptions
puts "Moving right along..."
end
'Inline' exception handling:
10 / 0 rescue puts "Please do not divide by zero."
puts "Moving right along..."
In the 'inline' case, the handler extends to the end of the line. You can have multiple statements if you use semicolons to separate them.
Note that throwing an exception from a destructor is also super bad mojo in C++. Basically any exception guarantees go out the window if you have destructors that throw. It's sufficiently bad that C++11 gave all destructors an implicit noexcept exception specification, meaning that an exception from a destructor will immediately call terminate() unless you specifically enable exceptions for the destructor for the class or one of the subobjects of that class contains a destructor which has exception enabled destructors.
Since all guarantees go out of the window if you throw in the destructor it is a *good thing* that destructors are marked noexcept, that way you have a guarantee that terminate is called, which I'll take over all kinds of undefined behavior (which throwing in the destructor will cause when used in conjunction with pretty much any library class or template which doesn't expect that... which includes all standard containers) any day.
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