gcc gdb 调试出现的奇怪现象，有遇到过的吗？

450 tmpquestlist = pqlist;
(gdb) n
454 sendbuflen = panaddr - psb;
(gdb)
452 memcpy(psb, prb, sizeof(MHEAD_T) + tres.qlen);
(gdb)
454 sendbuflen = panaddr - psb;
(gdb)
455 while(tmpquestlist)
(gdb)
454 sendbuflen = panaddr - psb;
(gdb)
457 //¸謇囈ݽs²ꑯ
(gdb) display sendbuflen
4: sendbuflen = 34
(gdb) n
460 tmprrslist = data;
4: sendbuflen = 34
(gdb)

源码是：
450 tmpquestlist = pqlist;
451 /¸´׆messageµèeadº̱uest²¿·ֵ½ЬӦ˽¾ݵèeadº̱uestא/
452 memcpy(psb, prb, sizeof(MHEAD_T) + tres.qlen);
453 panaddr = psb + sizeof(MHEAD_T) + tres.qlen;
454 sendbuflen = panaddr - psb;
455 while(tmpquestlist)
456 {
457 //¸謇囈ݽs²ꑯ

很奇怪的现象啊，头一次遇到！

gdb 调试单步执行顺序乱了，还缺少了
注释行也在单步调试中显示了