Initialize pointer to struct inside another struct

Question

I have two pointer variables (prevGuiMsg and currGuiMsg) to a struct inside another struct definition in a C++ source-file:

typedef struct
{
    bool re_pop_required;
    bool concurrent_popups;
    MlGuiMsg* prevGuiMsg;
    MlGuiMsg* currGuiMsg;
    uint32_t first_popup;
    uint32_t second_popup;
}RePopup;

The M1GuiMsg-struct is defined inside a different C header-file (I'm mixing C and C++ code). A pointer to the struct is passed as an argument to a function in the source file, where I wish to store the data that the parameter points to in the pointer variables prevGuiMsg and currGuiMsg.

I wish to explicitly declare a variable of the type struct RePopup and initialize its members along with the declaration in the C++ source file:

RePopup rp = {false, false, 0, 0, 0, 0};

My question is therefore: can/should one initialize a pointer to a struct with zero inside the explicit declaration of another struct?

Alan Birtles · Accepted Answer · 2019-01-15 12:48:42Z

3

You should use nullptr rather than 0 but otherwise there is nothing wrong with initialising a pointer to 0.

answered Jan 15, 2019 at 12:48

Alan Birtles

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6 Comments

Abdel Aleem Over a year ago

What is the advantage of using nullptr rather than 0?

thomas_f Over a year ago

If he's using C++11 or newer, yes.

aschepler Over a year ago

@AbdelAleem It wouldn't make a technical difference for directly initializing a pointer member like this, but it can make a difference in some cases involving overloaded functions and/or templates. So it's a good practice to use it by default for all pointers, and it also makes the intent of the code clearer.

Alan Birtles Over a year ago

It means you are being explicit that you are null initialising a pointer. Also you will get an error if you accidentally try to assign nullptr to an integer. e.g. if you mistyped your initialiser as {false, false, 0, nullptr, nullptr, 0} it wont compile

Lightness Races in Orbit Over a year ago

@AbdelAleem Self-documentingness only in this particular case, but it's a good habit generally.

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