C++ object declaration and no default constructor (user-declared or implicitly-declared)

Question

If I have

class Something
{
public:
    Something(int whatever) : whatever_(whatever) {}
private:
    int whatever_;
}

Then what happens when I create an object on the stack

Something something;

since there is no default constructor?

KamilCuk · Accepted Answer · 2019-01-18 03:00:12Z

1

On a conforming compiler you get a compilation error.

The following code:

class Something
{
public:
    Something(int whatever) : whatever_(whatever) {}
private:
    int whatever_;
};

Something something;

When compiled with gcc8.2 results in the following compilation error:

<source>:9:11: error: no matching function for call to 'Something::Something()' 
 Something something;
           ^~~~~~~~~    
<source>:4:5: note: candidate: 'Something::Something(int)'    
     Something(int whatever) : whatever_(whatever) {}    
     ^~~~~~~~~    
<source>:4:5: note:   candidate expects 1 argument, 0 provided    
<source>:1:7: note: candidate: 'constexpr Something::Something(const Something&)'    
 class Something    
       ^~~~~~~~~    
<source>:1:7: note:   candidate expects 1 argument, 0 provided    
<source>:1:7: note: candidate: 'constexpr Something::Something(Something&&)'    
<source>:1:7: note:   candidate expects 1 argument, 0 provided    
Compiler returned: 1

Live example available at godbolt.

edited Jan 18, 2019 at 3:00

answered Jan 18, 2019 at 2:57

KamilCuk

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4 Comments

Martin F Over a year ago

Can you add a ; after the last } and try again? It compiles for me.

KamilCuk Over a year ago

Yes, a typo, fixed.

KamilCuk Over a year ago

@MartinF So what compiler, compiler version and compiler options are you using?

Martin F Over a year ago

The problem was that I didn't do a clean build after removing the default constructor. It's complaining now. Sorry...

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