struct tm 在通过 function 时变为 PST

Question

Good day, I have a problem with struct tm that is in GMT but when passed through a function, it minuses 8 hours and turns to my local time (PST)

void TestFunction(glob_t* globbuf, struct tm *tm)
{
    char buffx[300];
    time_t timeif = timegm(tm);


    strftime(buffx, 100, "%Y-%m-%d %H:%M:%S.000", gmtime(&timeif));
    //print the buffx
    // the print shows the time in PST, -8 hours from what it was because at this point tm becomes
    // PST
}

int main()
{
    time_t t = time(NULL);
    struct tm *tm = gmtime(&t);
    tm->tm_sec = 0;

    char buffx[300];
    time_t timeif = timegm(tm);


    strftime(buffx, 100, "%Y-%m-%d %H:%M:%S.000", gmtime(&timeif));
    //print the buffx
    // Prints the time in GMT.
    // Do some other unrelated stuff

    TestFunction(&unRelatedParameterOne, tm); // Variable tm is in GMT

    return 0;
}

Answer 1

I instead pass on time_t timeif to the function now. This works as time if does not change when passed through a function.

I still do not know why struct tm would change time zone.