Re: void* passed as funtion parameters?

Hello Uli,

Sorry for bothering you with the sample, that was very nice of you to take
time and get back with a sample code. It is very appreciated.

I have entered your solution in VC++ compiler to try it, but I do get the
following warning:

1>c:\_dts_programming\c_programming\c\c_tests\c_string_samples\misc_c_samples\enumpointer.c(59)
: warning C4715: 'get_f1' : not all control paths return a value

But before discussing the warning, I have a 2 questions and I will outline
them at the end of this post. In the mean time here is how I tried it, note I
typedefed my structs though:

================================

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

enum type {type_pc, type_ddlb};

// TABLES
typedef struct tag_pc_table
{
long z;
long h;
}pc_table;

typedef struct tag_lb_table
{
long z;
long u;
}lb_table;

// OBJECTS
typedef struct tag_pc {
long w;
struct tag_pc_table *dc;
enum type type;
} pc;

typedef struct tag_lb {
long w;
struct tag_lb_table *dc;
enum type type;
} lb;

void* get_f1(void* p)
{
enum type* t = p;

switch(*t)
{
  case type_pc:
  {
   struct pc* pc = p;
   return pc; //pc->f1;
  }
break;

case type_ddlb:
  {
   struct ddlb* ddlb = p;
   return ddlb; //ddlb->f1;
  }
break;
}
}

int main()
{
long t;
pc *a;
lb *b;

pc_table apc[] = {101, 201, 301, 302}; // Fill table
lb_table alb[] = {102, 202, 401, 402}; // Fill table

a = malloc(sizeof (struct tag_pc));
get_f1(a);

b = malloc(sizeof (struct tag_lb));
get_f1(b);

free(a);
free(b);
return 0;
}
=================================

1- One thing I don't get is when I pass in the "a" variable when calling the
get_f1() function, its address gets assigned to *t byt he following line: in
the get_f1() function:

enum type* t = p;

and then we put *t in the switch command/case command, but the type_pc and
type_ddlb are 0, and 1 respectively and really don't match with (*t) ?

2- Why are we returning pc->f1, I don't think f1 is a member of the
structures?

3- What are we supposed to return? >>> pc or ddlb?

Anyhow, I have been experimenting with this and it turns out that you guys
were right that it works without implicitly casting to the correct type. I am
still scratching my head on that one as to why it would still work. I didn't
use any templates, macro functions or base structs. I will post the example
in a new post... this one has pretty well got its usage! The new post will be
called "No casting of void*"

Uli, I still am currious about the questions I asked here!

Thanks for your input!

--
Best regards
Roberto

"Ulrich Eckhardt" wrote: