c - qsort compare function behaviour -

everyone. trying change compare function , okay if write sth 0 -5.5 in infile output recive (after qsort) -5.5 greater 0, , that's not true. check code , tell me should chage?

    int compare(const void *str1, const void *str2)     {     char *number1, *number2;     int len1=0, len2=0, dot1=0, dot2=0, value=0;     int minus1=0, minus2=0;      number1 = *(char**)str1;     number2 = *(char**)str2;      while(*number1=='0') number1++;     while(*number2=='0') number2++;      while(*number1 || *number2){         if(value==0) {value= *number1-*number2;}          if(*number1){             if(*number1=='-') number1++;             if(*number1=='-') minus1=1;             if(*number1!='.'){                 number1++;                 if(dot1==1) len1++;}                  if(*number1=='.'){                     number1++;                     dot1=0;}         }          if(*number2){             if(*number2=='-') number2++;             if(*number2=='-') minus2=1;             if(*number2!='.'){                 number2++;                 if(dot2==1) len2++;}                  if(*number2=='.'){                     number2++;                     dot2=0;}         }     }      if(minus1>0 && minus2==0){return -1;}     if(minus1==0 && minus2>0){return 1;}     if(minus1>0 && minus2>0){         if(len1>len2) return -1;         if(len2>len1) return 1;         return (-value);}         if(len1>len2) return 1;         if(len2>len1) return -1;         return value; } 

i suggest use double array treated qsort , bsearch.

but if insist use char *:

int compare( const void * l, const void * r ) {    char * lerr  = null;    char * rerr  = null;    double left  = strtod((const char *)l, &lerr );    double right = strtod((const char *)l, &rerr );    return (*lerr||*rerr) ? (int)(l-r) : (int)(left-right); } 

documentation of strtod