问题调用(未声明)函数

问题描述

我们正在计算圆半径

We are computing circle radius

846:      r  = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
005AE147   fld         qword ptr [x2]
005AE14A   fsub        qword ptr [x1]
005AE14D   fld         qword ptr [x2]
005AE150   fsub        qword ptr [x1]
005AE153   fmulp       st(1),st
005AE155   fld         qword ptr [y2]
005AE158   fsub        qword ptr [y1]

005AE15B   fld         qword ptr [y2]

< ---- EIP = 005AE15B下一步操作要做

<---- EIP = 005AE15B Next Operation To do

005AE15E   fsub        qword ptr [y1]
005AE161   fmulp       st(1),st
005AE163   faddp       st(1),st
005AE165   sub         esp,8
005AE168   fstp        qword ptr [esp]
005AE16B   call        _sqrt (006d0e94)
005AE170   add         esp,8
005AE173   fstp        qword ptr [r]

直到这里没事

Until here all right

ST0 = +0.00000000000000000e+0000
ST1 = +1.00000000000000000e+0000
ST2 = 1#IND
ST3 = 1#IND
ST4 = 1#IND
ST5 = 1#IND
ST6 = 1#IND
ST7 = 1#IND

之后
005AE15B fld qword ptr [y2]
在堆栈顶部?

after this
005AE15B fld qword ptr [y2]
at the top of the stack this?

ST0 = 1#IND
ST1 = +0.00000000000000000e+0000
ST2 = +1.00000000000000000e+0000
ST3 = 1#IND
ST4 = 1#IND
ST5 = 1#IND
ST6 = 1#IND
ST7 = 1#IND
CTRL = 027F STAT = 5A61
TAGS = A1AA EIP = 005AE15B
CS = 001B DS = 0023

编译器VC6，带有所有修补程序的Windows XP SP2，处理器Pentium m 1.7Ghz(Centrino)

Compiler VC6, Windows XP SP2 with all patches, processor Pentium m 1.7Ghz (Centrino)

推荐答案

r  = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)); 

我们称之为:

we call:

distance=me_pnt_dist_2d(p_mt->pref, pc);
if(fabs(distance-radius)<p_mt->fOsnap){
    p_mt->bFind=1;
    return(0);
}
return(0);

未声明me_pnt_dist_2d的地方，

where me_pnt_dist_2d was undeclared ,

double me_pnt_dist_2d(PNT_2D *p1, PNT_2D *p2);

编译器假定返回的是int，因此
我们将fabs()的值引导到
处理器处于不一致状态.
奇怪的是，代码的一部分运行良好.

846:r = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));

005AE147 fld qword ptr [x2]
005AE14A fsub qword ptr [x1]
005AE14D fld qword ptr [x2]
005AE150 fsub qword ptr [x1]
005AE153 fmulp st(1)，st
005AE155 fld qword ptr [y2]
005AE158 fsub qword ptr [y1]

the compiler assumes returning int, so
we call fabs() with a value that leads the
processor in an inconsistent state.
The strangeness is that part of the code works well.

846: r = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));

005AE147 fld qword ptr [x2]
005AE14A fsub qword ptr [x1]
005AE14D fld qword ptr [x2]
005AE150 fsub qword ptr [x1]
005AE153 fmulp st(1),st
005AE155 fld qword ptr [y2]
005AE158 fsub qword ptr [y1]

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