Re: lua.h and c++

[David Jones <drj@...>]

On Sep 29, 2004, at 12:41, Daniel Walker wrote:

> Unfortunately I can't really accept that solution as the
> necessity for it is the exact problem I wished to address.
> Furthermore, you may notice that
>
>  #ifndef LUA_API
>  #ifdef __cplusplus
>  #define LUA_API extern "C"
>  #else
>  #define LUA_API extern
>  #endif
>  #endif
>
> is perfectly valid C code, which completely eliminates the
> need for any C++ specifics, and would keep the issue in
> question from ever arising again. There really isn't any
> benefit in not writing a header like this, so why not?

That code is conforming C code, but not strictly conforming C code.  
Since it uses a pre-processor token ("__cplusplus") that is in the 
namespace reserved for the implementation, then any given C 
implementation is allowed to assigned whatever meaning it likes to that 
code.  Only the language C++ assigns a meaning to __cplusplus, the 
language C makes no guarantees.  It is only when you use a cooperating 
C implementation that __cplusplus will have the meaning you like.  In 
other words a C implementation is at perfect liberty to define the 
token __cplusplus for its own purposes.

Adding C++ code to the standard Lua distribution would require the 
maintainers to maintain the C++ code as well.  I'm sure they don't want 
to do that.

The standard way for a C++ program to include a C header file is to go:
extern "C" {
#include "c-header.h"
}
why is it that C++ programmers seem so squeamish about doing this?

Basically, I approve of the Lua maintainers' current position.

David Jones