(Standard C99) What value will be contained in z.lines.line12 after assignment of -1 if sizeof(int) = 4?
union ZZZ {
    unsigned long long plain;
    struct {
        unsigned int line0:1;
        unsigned int line1:2;
        unsigned int line2:3;
        unsigned int line3:4;
        unsigned int line4:5;
        unsigned int line5:6;
        unsigned int line6:7;
        unsigned int line7:8;
        unsigned int line8:7;
        unsigned int line9:6;
        unsigned int line10:5;
        unsigned int line11:4;
        unsigned int line12:3;
        unsigned int line13:2;
        unsigned int line14:1;
    }lines;
};

void main() {
    ZZZ z;
    z.plain = (unsigned long long)-1;
}
Explanation
Bit fields that cross the type boundary will skip bits to align bits to the next type, for example, for an integer (unsigned int) cannot cross the 32-bit boundary. The line12 bit field will be located in the 9th byte from the beginning of z, i.e. it will not be initialized.

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