Hi Walter,

I ran into a problem compiling foreign C-code. The authors write code like this:

  ------ Header file  pro.h ----
  typedef struct {
     int a, b, c;
  } ABC;
  void Func(ABC * ap, int ini);

  ----- Implementation  pro.c -----
  #include "pro.h"

  void Func(ABC * const ap, int ini)
  /*              ^^^^^^  */
  {
     ap->a = ini;
     ap->b = ini;
     ap->c = ini;
  }/*Func*/

According to postings in comp.lang.c this seems to be legal in ANSI-C.  DMC complains about const vs. non-const. It makes sense to treat both function prototypes the same as the passed by value parameters can't change from the callers view. Using const in the definition is a promise to the compiler that the passed value should not be modified in the function body. May also be a hint to the optimizer to generate better code?

I think this is also true for C++ code.


	Heinz



I would expect that this

Heinz Saathoff schrieb...
> 
> I think this is also true for C++ code.

I've just looked to the C++ standard. It's true here also. In chapter 8.3.5 (3) Functions I found this:

  "After producing the list of parameter types, several
   transformations take place upon these types to determine
   the function type. Any cv-qualifier modifying a parameter
   type is deleted. [Example: the type  void (*)(const int)
   becomes void (*)(int) -end example]. Such cv-qualifiers
   affect only the definition of the parameter within the body
   of the function; they do not affect the function type."

So this declarations are equal:

  void func(int);
  void func(const int);
  void func(volatile int);


Regards,
	Heinz

I've never run into that before. Thanks for posting it. I'll add it to the list to be fixed. -Walter

"Heinz Saathoff" <hsaat@bre.ipnet.de> wrote in message news:MPG.16ffcfd81cfe4dc198969e@news.digitalmars.com...
> Hi Walter,
>
> I ran into a problem compiling foreign C-code. The authors write code like this:
>
>   ------ Header file  pro.h ----
>   typedef struct {
>      int a, b, c;
>   } ABC;
>   void Func(ABC * ap, int ini);
>
>   ----- Implementation  pro.c -----
>   #include "pro.h"
>
>   void Func(ABC * const ap, int ini)
>   /*              ^^^^^^  */
>   {
>      ap->a = ini;
>      ap->b = ini;
>      ap->c = ini;
>   }/*Func*/
>
> According to postings in comp.lang.c this seems to be legal in
> ANSI-C.  DMC complains about const vs. non-const. It makes sense to
> treat both function prototypes the same as the passed by value
> parameters can't change from the callers view. Using const in the
> definition is a promise to the compiler that the passed value should not
> be modified in the function body. May also be a hint to the optimizer to
> generate better code?
>
> I think this is also true for C++ code.
>
>
> Heinz
>
>
>
> I would expect that this
>