??????些??????????????? C ???????
???????????? ???????[ 2015/10/14 11:54:54 ] ???????????????
??????????渭??????????????????????? C ?????????????????? C?????????????? C ???????些??????????????????懈???????????些??????????邪?????未??????????
????????????????????械????????????械???????????????械?????????????
????1.
????int i;
????int i = 10;
????Q????未??????????????????????????????味????鈥�??????????????????????????????????????????????蔚???????
????A????????未????????????????????????????????????????????械???????????????“????”??
????2.
????extern void bar(void);
????void foo(int *x)
????{
????int y = *x;
????/* (1) */
????if(!x)
????/* (2) */
????{
????return;
????/* (3) */
????}
????bar();
????return;
????}
????Q: ????写???????? x ?????? bar() ???????????????????????????????????????????????????????????
????A: ???????????????? x ??????未??????????????? (1) ?校? ????????????????????????????? (1) ?斜????? ??????????? (2) ?蟹???????????????械? (1) ?小??????????????????????????????????渭??????小????? (1) ?械???????????????? x ??????????????????? (2) ?泻? ?? (3) ?斜?????????????????? y ????????????????????????卸?????????????????? *x ????????????????volatile????
??????????????????蔚??????????效???????
????3.???????????????
????#define ZP_COUNT 10
????void func_original(int *xp?? int *yp?? int *zp)
????{
????int i;
????for(i = 0; i < ZP_COUNT; i++)
????{
????*zp++ = *xp + *yp;
????}
????}
????????????????路???????????
????void func_optimized(int *xp?? int *yp?? int *zp)
????{
????int tmp = *xp + *yp;
????int i;
????for(i = 0; i < ZP_COUNT; i++)
????{
????*zp++ = tmp;
????}
????}
????Q???????????????????????????????????? zp ????锌????貌???????
????A????????????? yp == zp ?????????
????4.
????double f(double x)
????{
????assert(x != 0.);
????return 1. / x;
????}
????Q: ???????????????????纾╥nf?? ?????韪�?????????????IEEE 754 ???????????????????械?? ?????????????????NDEBUG ????斜????澹�??
????A???????????????????????????娣�???? x ????????? 1e-309.
??????

???路???
??????????????????
2023/3/23 14:23:39???写?貌??????????
2023/3/22 16:17:39????????????????????些??
2022/6/14 16:14:27??????????????????????????
2021/10/18 15:37:44???????????????
2021/9/17 15:19:29???路???????路
2021/9/14 15:42:25?????????????
2021/5/28 17:25:47??????APP??????????
2021/5/8 17:01:11