prevent multi-call in Assert.
If cond calls malloc and failed at the first time, but success at the second time, nemu will execute line 35-38 and output error info but do not stop at line 39.
Since line 34 make sure that cond is 0. assert(0) in line 39 is fine.
prevent multi-call in Assert. If cond calls malloc and failed at the first time, but success at the second time, nemu will execute line 35-38 and output error info but do not stop at line 39. Since line 34 make sure that cond is 0. assert(0) in line 39 is fine.