在 2020/5/24 21:31, Thamilarasu Kandasamy (thamil) via Gcc-help 写道: > > int size = 100; > unsigned int usize = 100; > > result1 = (void *) (((uintptr_t) &var) & ~(size - 1)); > result2 = (void *) (((uintptr_t) &var) & ~(usize - 1)); > result3 = (void *) (((uintptr_t) &var) & ~((unsigned long int)usize - 1)); > `result1` is bitwise AND `&var` with `(uintptr_t)~(int)99` which is `(uintptr_t)(int)-100` which is probably `0xFFFFFFFFFFFFFF9C` on a 64-bit machine. `result2` is bitwise AND `&var` with `(uintptr_t)~(unsigned)99` which is likely `(uintptr_t)(unsigned)4294967196` which is `0xFFFFFF9C` on a 64-bit machine. So higher half is truncated as expected. `result3` is bitwise AND `&var` with `(uintptr_t)~(unsigned long)99` which is probably `0xFFFFFFFFFFFFFF9C` on a 64-bit machine. There is no bug. -- Best regards, LH_Mouse
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