looser throw specifier for virtual...

This is a discussion on looser throw specifier for virtual... within the C++ Programming forums, part of the General Programming Boards category; Hey, here's the error: "error: looser throw specifier for virtual OutOfMemory::~OutOfMemory " What does it mean, why does it happen, ...

  1. #1
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    looser throw specifier for virtual...

    Hey, here's the error: "error: looser throw specifier for virtual OutOfMemory::~OutOfMemory
    "
    What does it mean, why does it happen, what do i do to fix? Thanks. (Compiling with GNU compiler)
    Code:
    #include <exception>
    
    using namespace std; 
    
    class OutOfMemory : public std::exception
    {
    	private: 
    		string identification; 
    	
    	public:
    		OutOfMemory(string ident) : identification(ident) {}
    		string what() { return "identification"; }		
    };

  2. #2
    The larch
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    My compiler continues the error message:
    overriding `virtual std::exception::~exception() throw ()'
    Apparently OutOfMemory should have a destructor which promises not to throw, too.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  3. #3
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    Unhappy

    I've never seen a declaration like that before and I don't really know how to promise things to the compiler

  4. #4
    C++ Witch laserlight's Avatar
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    Basically, you define:
    Code:
    ~OutOfMemory() throw() {}
    Incidentally, I note that what() returns a const char*, and is const, and apparently also has throw().

    EDIT:
    Interestingly, I do not recall having to bother with this, but then the only exception classes I have written derive from a subclass of std::exception, e.g., std::logic_error. As such, I could use the constructor that takes a string instead of providing my own string member variable.

    I suggest that you do the same.
    Last edited by laserlight; 02-08-2008 at 09:56 AM.
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  5. #5
    Kernel hacker
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    Quote Originally Posted by laserlight View Post
    Incidentally, I note that what() returns a const char*, and is const, and apparently also has throw().
    You mean that it SHOULD, because right now it calls the std::string constructor with a constant string. This may well cause a memory exception in itself, if the system is very low on memory, since the string constructor will have to allocate memory to store the string.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
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  6. #6
    C++ Witch laserlight's Avatar
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    You mean that it SHOULD
    No, it does, since we are talking about a method that is supposed to be overriden. At the moment the what() hides the virtual function inherited.

    This may well cause a memory exception in itself, if the system is very low on memory, since the string constructor will have to allocate memory to store the string.
    I think that is related to the current compile error, though I do not quite understand why it affected the destructor instead of the constructor.
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  7. #7
    and the hat of sweating
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    Quote Originally Posted by matsp View Post
    You mean that it SHOULD, because right now it calls the std::string constructor with a constant string. This may well cause a memory exception in itself, if the system is very low on memory, since the string constructor will have to allocate memory to store the string.

    --
    Mats
    I'm guessing std::terminate() would be called and your program would abort if that happened?

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