Help: Convert C to C++

Hello,
I'm trying to convert a program from C to C++.

Code:

 
#define RANDSIZL   (4)  /* I recommend 8 for crypto, 4 for simulations */
#define RANDSIZ    (1<<RANDSIZL)

/* context of random number generator */
struct randctx{
  int randcnt;
  int randrsl[RANDSIZ];
  int randmem[RANDSIZ];
  int randa;
  int randb;
  int randc;
};

typedef  struct randctx  randctx;

The typedef line doesn't make sense to me. A new name (randctx) for struct randctx? If I delete the typedef line it should still compile, but it doesn't. Any idea why? What's the point of having such a typedef line?

A new name (randctx) for struct randctx?

Yes.

If I delete the typedef line it should still compile, but it doesn't.

Did you compile with a C++ compiler?

Any idea why? What's the point of having such a typedef line?

So that you can use the name randctx instead of struct randctx, but obviously this does not apply in C++.

The code I posted compiles both wit h gcc and g++. The program that I'm converting won't compile (gcc) if I remove the typedef line.

What's the easiest way to convert C to C++ if you don't know C?

Compile the program as it is with a C++ compiler, and fix the errors.

It should work. Otherwise, what's the error?

I can't post the error cause it's too big. The program that I'm trying to convert to c++ is called Flam3.

Post a few compile errors first. Fix them. Go on to the next.

Originally Posted by Arlenik

Code:

 
/* context of random number generator */
struct randctx{
  int randcnt;
  int randrsl[RANDSIZ];
  int randmem[RANDSIZ];
  int randa;
  int randb;
  int randc;
};

typedef  struct randctx  randctx;

The typedef line doesn't make sense to me. A new name (randctx) for struct randctx? If I delete the typedef line it should still compile, but it doesn't. Any idea why? What's the point of having such a typedef line?

In C, the declaration of struct randctx declares a struct tag named "randctx" and (effectively) a type named "struct randctx". The typedef makes randctx an alternative name for the type "struct randctx".

In C++, the declaration of struct randctx implicitly also declares a type named randctx, so the typedef is not required.

Hence you can expect the above to compile happily with a C compiler, but not with a C++ compiler (with some ambiguity in that statement depending on compatibility settings supported by some compilers).

Compiles just fine even in pedantic mode. C++ was made with C compatibility in mind, and therefore has no problem with a typedef overriding the struct name.