CODEWITHSUNDEEP
c++
Rajeshwar
Rajeshwar

Reputation: 11651

Initialization of a pointer

I am currently confused with the following statement - I though this statement would yield an error during compile time however it doesn't. 

// statement 1:
someclass* q(someclass());

I understand if the statement was like this

// statement 2:
someclass* q(&someclass());

I would like to know why statment 1 doesnt generate an error or even if that is valid (is there anything I am missing behind the scenes ?)

Upvotes: 5

Views: 166

Answers (2)

Andy Prowl
Andy Prowl

Reputation: 126432

I would like to know why statment 1 doesnt generate an error or even if that is valid

The first statement is valid, although it is probably not doing what you expect: this statement is declaring a function named q which returns a pointer to an object of type someclass and takes in input a function which in turn accepts no arguments and returns an object of type someclass. This is called the Most Vexing Parse.

The second statement is not valid: it is trying to declare a pointer named q to an object of type someclass, and initialize this pointer to the address of the object constructed by the someclass() expression. Notice, however, that someclass() is a temporary, and taking the address of a temporary is illegal.

Upvotes: 12

Mankarse
Mankarse

Reputation: 40603

Statement 1 is actually a declaration for a function. This function is called q, and takes a pointer to a function taking no arguments and returning a someclass, and returns a pointer to someclass.

See Most Vexing Parse.

Upvotes: 3

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