C: Dynamic string using variable number of arguments

[negru]

I need to create dynamic string by given format(%d,%s,%f,%lf,%c) using variable number of arguments in function. This code gives me an error(main.exe has stopped working):

    #include<stdio.h>
    #include<stdarg.h>
    #include<string.h>
    #include<stdlib.h>

    char *form(char *format,...);
    char *form(char *format,...)
    {
        char *res=(char *)calloc(1,1),val_int[12],*pos_int,*val_str,*pos_str,*val_float,*pos_float,*val_lf,*pos_lf,*val_char,*pos_char;
        va_list args;
        va_start(args,format);
        do
        {
          pos_int=strstr(format,"%d");pos_str=strstr(format,"%s");pos_float=strstr(format,"%f");pos_lf=strstr(format,"%lf");pos_char=strstr(format,"%c");
          if(pos_int && (!pos_str || pos_int < pos_str) && (!pos_float || pos_int < pos_float) &&
             (!pos_lf || pos_int < pos_lf) && (!pos_char || pos_int < pos_char))
          {
            itoa(va_arg(args,int),val_int,10);
            res=(char *)realloc(res,strlen(res)+(pos_int-format)+strlen(val_int)+1);
            strncat(res,format,pos_int-format);
            strcat(res,val_int);
            format=pos_int+2;
          }
          else if(pos_str && (!pos_int || pos_str < pos_int) && (!pos_float || pos_str < pos_float) &&
                  (!pos_lf || pos_str < pos_lf) && (!pos_char || pos_str < pos_char))
          {
             val_str=va_arg(args,char *);
             res=(char *)realloc(res,strlen(res)+(pos_str-format)+strlen(val_str)+1);
             strncat(res,format,pos_str-format);
             strcat(res,val_str);
             format=pos_str+2;
          }

          else if(pos_float && (!pos_int || pos_float < pos_int) && (!pos_str || pos_float < pos_str) &&
                  (!pos_lf || pos_float < pos_lf) && (!pos_char || pos_float < pos_char))
          {
             fcvt(va_arg(args,double),val_float,6,0);
             res=(char *)realloc(res,strlen(res)+(pos_float-format)+strlen(val_float)+1);
             strncat(res,format,pos_float-format);
             strcat(res,val_float);
             format=pos_float+2;
          }

          else if(pos_lf && (!pos_int || pos_lf < pos_int) && (!pos_str || pos_lf < pos_str) &&
                  (!pos_float || pos_lf < pos_float) && (!pos_char || pos_lf < pos_char))
          {
              ecvt(va_arg(args,double),val_lf,6,0);
              res=(char *)realloc(res,strlen(res)+(pos_lf-format)+strlen(val_lf)+1);
              strncat(res,format,pos_lf-format);
              strcat(res,val_lf);
              format=pos_lf+2;
          }
          else if(pos_char && (!pos_int || pos_char < pos_int) && (!pos_str || pos_char < pos_str) &&
                  (!pos_float || pos_char < pos_float) && (!pos_lf || pos_char < pos_lf))
          {
              val_char=va_arg(args,char *);
              res=(char *)realloc(res,strlen(res)+(pos_char-format)+strlen(val_char)+1);
              strncat(res,format,pos_char-format);
              strcat(res,val_char);
              format=pos_char+2;
          }
        }
        while(pos_int || pos_str || pos_float || pos_lf || pos_char);
        va_end(args);
        res=(char *)realloc(res,strlen(res)+strlen(format)+1);
        strcat(res,format);
        return res;
    }

    int main()
    {
        char *s;
        s=form("John is %d years old and has an %c in %s. He is going to school for %lf years.",9,'A',"maths",1.5);
        printf("%s",s);
        free(s);
        return 0;
    }

I assume the error is in functions(itoa,fcvt,ecvt). Thanks for replies.

 

[xwb]

Which compiler are you using? It should have told you that the parameter types for fcvt and ecvt are incorrect. The 2nd parameter is the number of decimal places/number of digits