initialize multiple bools in c++

Question

I have some input flags in a C++ program, they all start out false. I thought it might be nice, if I could initialize all of them to false. So I tried:

bool flagA, flagB, flagH = false;

but the flags did not get set properly, when I tried this. flagA evidently was initialized as true? Setting the flags explicitly works.

bool flagA = false;
bool flagB = false;
bool flagH = false;

I am using g++, and I do not get compiler errors or warnings. I know the program is misbehaving because flagA when set true sends program output to the local printer. Just wondering.

If you declare them as global scope then all start with false. — ashiquzzaman33, Oct 24 '15 at 14:18

score 5 · Accepted Answer · answered Oct 24 '15 at 14:14

5

When compiler sees bool flagA, flagB, flagH = false; he translates is as

User needs three bool values, named flagA, flagB and flagC. Oh, and flagC shall be initialized to false.

It's just shorter writing for

bool flagA;
bool flagB;
bool flagC = false;

And since they are local scope variables (probably), they are not guaranteed to be initialized with default value.

answered Oct 24 '15 at 14:14

Zereges

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In C++, bools are objects right? So, won't the default contructor kick in and initialize to 0? – nirvanaswap Aug 11 '17 at 16:54
@nirvanaswap In C++, `bool` is not object and no default construction happens. But you can force default initialization using `bool flagA{};`. – Zereges Aug 12 '17 at 16:49

initialize multiple bools in c++

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