Initializing default values in a struct

Yes. bar.a and bar.b are set to true, but bar.c is undefined. However, certain compilers will set it to false.

See a live example here: struct demo

According to C++ standard Section 8.5.12:

if no initialization is performed, an object with automatic or dynamic storage duration has indeterminate value

For primitive built-in data types (bool, char, wchar_t, short, int, long, float, double, long double), only global variables (all static storage variables) get default value of zero if they are not explicitly initialized.

If you don’t really want undefined bar.c to start with, you should also initialize it like you did for bar.a and bar.b.

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