How pass NULL for a parameter in a function?

This is a discussion on How pass NULL for a parameter in a function? within the C++ Programming forums, part of the General Programming Boards category; While the below compiles (g++ compiler) it throws a runtime error "terminated in an unusual way." How can I allow ...

  1. #1
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    Nov 2006
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    How pass NULL for a parameter in a function?

    While the below compiles (g++ compiler) it throws a runtime error "terminated in an unusual way." How can I allow passing NULL?

    Code:
    void doSmth(std::string str)
    {
          //This causes the error only if NULL was actually passed
         if ( &str == NULL ) printf( "null" );
    }
    
    int main(...)
    {
         //This one works fine
         doSmth( "string" );
    
         //This cause it to crash
         doSmth( NULL );
    
         //This will also cause a crash
         std::string tmp(NULL);
         doSmth( tmp );
    }

  2. #2
    Registered User
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    Jan 2005
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    7,344
    Do you just want to pass an empty string? Use string() or "" to do that.

    If you want something that is different than an empty string (because an empty string means something else) then you want to overload doSmth or have it take a pointer parameter that can be null.

  3. #3
    Registered User
    Join Date
    Nov 2006
    Posts
    184
    Cool.

    BTW, thank you to all of you guys who have been VERY helpful to someone learning c++. I really appreciate it!

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