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incompatible warning in C/C++

I am using MS Visual C/C++ 6.0. I get the following warning when compiling

C:model.ex.c(1221) : warning C4133: '=' : incompatible types - from
'struct s_lsp_def *' to 'struct s_lsp_def *'


In the .h file, I have
======================

typedef struct s_lsp_def;

typedef struct
{
int lsp_id;
int priority;


struct s_lsp_def* ptr_next_lsp_def;


}s_lsp_def;

in a .c file, model.ex.c, I have
================================

int bcModel_add_lspToList ( s_lsp_def* the_ptr_lsp_def,
{

s_lsp_def* curr_ptr_lsp_def;

// the following line is the PROBLEM

curr_ptr_lsp_def->ptr_next_lsp_def = the_ptr_lsp_def;


}


Does anyone understand why this warning.
Thanks.

Ali wrote:
> incompatible warning in C/C++
>
> I am using MS Visual C/C++ 6.0. I get the following warning when compiling
>
> C:model.ex.c(1221) : warning C4133: '=' : incompatible types - from
> 'struct s_lsp_def *' to 'struct s_lsp_def *'
>
>
> In the .h file, I have
> ======================
>
> typedef struct s_lsp_def;
>
> typedef struct
> {
> int lsp_id;
> int priority;
>
>
> struct s_lsp_def* ptr_next_lsp_def;
>
>
> }s_lsp_def;
>
> in a .c file, model.ex.c, I have
> ================================
>
> int bcModel_add_lspToList ( s_lsp_def* the_ptr_lsp_def,
> {
>
> s_lsp_def* curr_ptr_lsp_def;
>
> // the following line is the PROBLEM
>
> curr_ptr_lsp_def->ptr_next_lsp_def = the_ptr_lsp_def;
>
>
> }
>
>
> Does anyone understand why this warning.
> Thanks.
Try the following instead:
typedef struct
{
int lsp_id;
int priority;
s_lsp_def* ptr_next_lsp_def;
}s_lsp_def;

You don't need the struct, since you're doing a typedef

Ali wrote:
> incompatible warning in C/C++

There is no such thing as "C/C++". It's either C or it is C++. Find out
which and then post to the right newsgroup. If what you do is in fact C,
post to comp.lang.c. Post here again if it is (unlikely) C++.

> [...]

V

Axter wrote:
> [..]
> Try the following instead:
> typedef struct
> {
> int lsp_id;
> int priority;
> s_lsp_def* ptr_next_lsp_def;
> }s_lsp_def;
>
> You don't need the struct, since you're doing a typedef

In C++ you don't need any typedef. You simply write

struct s_lsp_def
{
...
s_lsp_def *ptr;
};

V

Axter wrote:
> Ali wrote:
>> incompatible warning in C/C++
>>
>> I am using MS Visual C/C++ 6.0. I get the following warning when compiling
>>
>> C:model.ex.c(1221) : warning C4133: '=' : incompatible types - from
>> 'struct s_lsp_def *' to 'struct s_lsp_def *'
>>
>>
>> In the .h file, I have
>> ======================
>>
>> typedef struct s_lsp_def;
>>
>> typedef struct
>> {
>> int lsp_id;
>> int priority;
>>
>>
>> struct s_lsp_def* ptr_next_lsp_def;
>>
>>
>> }s_lsp_def;
>>
>> in a .c file, model.ex.c, I have
>> ================================
>>
>> int bcModel_add_lspToList ( s_lsp_def* the_ptr_lsp_def,
>> {
>>
>> s_lsp_def* curr_ptr_lsp_def;
>>
>> // the following line is the PROBLEM
>>
>> curr_ptr_lsp_def->ptr_next_lsp_def = the_ptr_lsp_def;
>>
>>
>> }
>>
>>
>> Does anyone understand why this warning.
>> Thanks.
> Try the following instead:
> typedef struct
> {
> int lsp_id;
> int priority;
> s_lsp_def* ptr_next_lsp_def;
> }s_lsp_def;
>
> You don't need the struct, since you're doing a typedef
>
Yes, but you can't use the typedef inside its own definition. But you
can use the incomplete struct type itself. You just need to name it
before using it, like so:

typedef struct s_lsp_def
{
int lsp_id;
int priority;

struct s_lsp_def* ptr_next_lsp_def;

} s_lsp_def;


This is valid in both C and C++. In C++ you don't need the typedef,
because a struct name works like a class name, so you can always use it
without putting 'struct' in front of it.

C++ only:

struct s_lsp_def
{
int lsp_id;
int priority;

s_lsp_def* ptr_next_lsp_def;

};

"Victor Bazarov" <> wrote in message
news:%%Zpf.58640$ o.verio.net...
> Ali wrote:
>> incompatible warning in C/C++
>
> There is no such thing as "C/C++". It's either C or it is C++. Find out
> which and then post to the right newsgroup. If what you do is in fact C,
> post to comp.lang.c. Post here again if it is (unlikely) C++.
>
>> [...]
>
> V

Actually, since c++ allows C code, I think your statement is a bit
misleading Victor.

I've seen "There is no such thing as "C/C++" too many times on this
newsgroup and it is quite obvious what that the poster means "in C or
C++...".

Have you no concept of what / means?

Jim Langston wrote:
> "Victor Bazarov" <> wrote in message
> news:%%Zpf.58640$ o.verio.net...
> > Ali wrote:
> >> incompatible warning in C/C++
> >
> > There is no such thing as "C/C++". It's either C or it is C++. Find out
> > which and then post to the right newsgroup. If what you do is in fact C,
> > post to comp.lang.c. Post here again if it is (unlikely) C++.
> >
> >> [...]
> >
> > V
>
> Actually, since c++ allows C code, I think your statement is a bit
> misleading Victor.
>
> I've seen "There is no such thing as "C/C++" too many times on this
> newsgroup and it is quite obvious what that the poster means "in C or
> C++...".
>
> Have you no concept of what / means?

I have no concept of what "in C or in C++" means. They are different
languages and solutions to the same problem in one language are often
inappropriate or even incorrect in the other. So whether you say "in
C/C++" or in "in C or in C++" you are probably doing so because you
don't realise that, either way, it's a meaningless question.

The use of "C/C++" seems to me to imply some muddled thinking along the
lines of " I know they are kind of different but C++ is just a better C
so they are basically the same thing". In which case, correcting that
muddles thinking, as I think Victor did, is helpful.

Gavin Deane

Victor Bazarov wrote:
> Ali wrote:
> > incompatible warning in C/C++
>
> There is no such thing as "C/C++". It's either C or it is C++. Find out
> which and then post to the right newsgroup. If what you do is in fact C,
> post to comp.lang.c. Post here again if it is (unlikely) C++.
>
> > [...]
>
> V

It is true there is no such language as C/C++ however you might want to
write header files that are compatible with both languages, as both
languages have the concept of a header file.

> typedef struct s_lsp_def;

Is that a valid forward declaration? typedef struct s_lsp_def to what?
Presumably you want to say that s_lsp_def is a typedef to an unknown
struct. I don't think that's allowed although it would be nice if it
were.

Now to answer the original problem, if you want to use the
struct/typedef features that is used in C then you should give the
struct a name, maybe s_lsp_def_tag. Then you can use that also within
the struct itself thus:

typedef struct s_lsp_def_tag
{
// code including a pointer to its own type
} s_lsp_def;

although I don't think you could use s_lsp_def for a forward
declaration.

"Jim Langston" <> writes:

> "Victor Bazarov" <> wrote in message
> news:%%Zpf.58640$ o.verio.net...
> > Ali wrote:
> >> incompatible warning in C/C++
> >
> > There is no such thing as "C/C++". It's either C or it is C++. Find out
> > which and then post to the right newsgroup. If what you do is in fact C,
> > post to comp.lang.c. Post here again if it is (unlikely) C++.
> >
> >> [...]
> >
> > V
>
> Actually, since c++ allows C code, I think your statement is a bit
> misleading Victor.

I think the statement above is more than a bit misleading.

A c++ compiler compiles C++ code. A c compiler compiles c code. C++
does *not* compile C code.

Try the following in your favorite c++ compiler:

struct class
{
enum { zero, one, two, three } new;
};

int main(void)
{
struct class throw;
return 0;
}

Or the following:

#include <stdlib.h>

int main(void)
{
int *x = malloc(1000 * sizeof *x);
/* do something useful with x */
free(x);
return 0;
}

/Niklas Norrthon

Earl Purple wrote:
> Victor Bazarov wrote:
>> typedef struct s_lsp_def;

I didn't write that.

> Is that a valid forward declaration? typedef struct s_lsp_def to what?
> Presumably you want to say that s_lsp_def is a typedef to an unknown
> struct. I don't think that's allowed although it would be nice if it
> were.

You should simply write

struct s_lsp_def;

At least in C++ it's a valid forward-declaration of 's_lsp_def' as
a struct (class).

> [..]

V