Managed code, .H and .CPP

[Guest]

When creating forms with Visual C++ 2005, all the code for building the
interface (the InitializeComponent method) and event handlers are set in the
..H file, as they were inline methods. So I ask, for managed code they are
effectively inline methods or they are handled indifferently if they are in
the class declaration or outside of it? Do I still have to write declarations
and definitions in different files for avoiding multiple compiling when
including the headers or it is handled more like C# for managed code?

Thank you,
Ignazio

 

[Carl Daniel [VC++ MVP]]

When creating forms with Visual C++ 2005, all the code for building
the interface (the InitializeComponent method) and event handlers are
set in the .H file, as they were inline methods. So I ask, for
managed code they are effectively inline methods or they are handled
indifferently if they are in the class declaration or outside of it?
Do I still have to write declarations and definitions in different
files for avoiding multiple compiling when including the headers or
it is handled more like C# for managed code?

Methods defined in the class body are (I believe) NOT implicitly inline in a
managed class - they have to be represented in the IL as methods, and then
it's up to the JIT to inline them if it decides to.

That said, methods defined in the class definition are linked "as if" they
were inline, just as with standard C++, and fairly analogously to C#.

-cd

 

[Guest]

Thank you. If I understood well, I can write all the code of the forms in
their .H without any problem.
The only problem is with cross-dependance of two classes. For example:

// A.h
#include "B.h"

ref class A {
void f () {
B::g();
}
void g () {
Console::WriteLine("test");
}
};

// B.h
#include "A.h"
ref class B {
void g() {
A::g();
}
};

The compiler encounters an error, as it is right to do in C++. So, it is
necessary to write a header and a cpp file for one of the two classes...
Don't you find it a little tricky that I need just the .H for some files and
both for other files?

Ignazio

 

[Carl Daniel [VC++ MVP]]

Thank you. If I understood well, I can write all the code of the
forms in their .H without any problem.
The only problem is with cross-dependance of two classes. For example:

// A.h
#include "B.h"

ref class A {
void f () {
B::g();
}
void g () {
Console::WriteLine("test");
}
};

// B.h
#include "A.h"
ref class B {
void g() {
A::g();
}
};

The compiler encounters an error, as it is right to do in C++. So, it
is necessary to write a header and a cpp file for one of the two
classes... Don't you find it a little tricky that I need just the .H
for some files and both for other files?

Yep.

You can thank C++'s one-pass compilation model for that. Until (and unless)
C++ adopts a multi-pass compilation model we'll always have that limitation.

-cd

 

[Guest]

There's an approach outlined by Stephen Fraser where you place all the code
in .h files (using #pragma once), and then in a single .cpp file you #include
all those .h files in the appropriate order.

This allows you to avoid the archaic separation of definition and
implementation (which had it's reasons 20 years ago, but is unnecessary with
modern IDE's).
--
David Anton
www.tangiblesoftwaresolutions.com
Instant C#: VB.NET to C# Converter
Instant VB: C# to VB.NET Converter
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[Guest]

Thank you.
Ignazio

Yep.

You can thank C++'s one-pass compilation model for that. Until (and unless)
C++ adopts a multi-pass compilation model we'll always have that limitation.

-cd

 

[Guest]

Yes, but there's some problem with that approach:
1. maybe even unmodified files are recompiled each time (the .cpp changes
because even only one .h is modified, and all the .h get recompiled)
2. look at the reply to Carl Daniel for the message I wrote about
cross-dependancy.

Thank you,
Ignazio

 

[Guest]

Right. I'm not so concerned about the excessive compilation, but the
cross-dependency issue is the show stopper to that approach.

I'm still waiting for the day when C++ compilers sort out these dependency
issues (like C#, VB, Java, etc.). Having worked a lot in these other
languages, it really does seem like a major step backwards to have to worry
about cross dependencies.
--
David Anton
www.tangiblesoftwaresolutions.com
Instant C#: VB.NET to C# Converter
Instant VB: C# to VB.NET Converter
Instant C++: C# to C++ Converter
Instant J#: VB.NET to J# Converter

 

[Peter Oliphant]

Hi Ignazio,

Personally, I try to put everything in the .H file. The reason is it makes
the generated code in-line (performance) and all in one place (source
organization). With so much RAM in computers nowadays it usually makes sense
to optimize for speed rather than size, and in-line usually contributes in
this regard.

However, there are times you MUST put stuff in a .CPP file. This is when you
have two classes which both must reference each other in a 'detailed' way
(i.e., each calls a method in the other). If just the pointer is needed to
an instance of another class, one can still stay in the .H by declaring the
other class before it is used without defining it.

That is, this is ok to stay in two different .H files:

--------------------------------
----------------------------------
header file A:

#include "B.h"
class A
{
void Method_A()
{
m_B_Ptr->Method_B() ;
} ;
:
B* m_B_Ptr ;
} ;
--------------------------------
header file B:

class A;
class B
{
:
A* m_A_Ptr ;
} ;
-------------------------------
-------------------------------
But this is NOT ok:
-------------------------------
-------------------------------
header file A:

#include "B.h"
class A
{
void Method_A()
{
m_B_Ptr->Method_B() ;
} ;
:
B* m_B_Ptr ;
} ;
-----------------------------
header file B:

class A; // replacing this with #include "A.h" causes circular definition
errors
class B
{
void Method_B()
{
m_A_Ptr->Method_A( ) ; // error since doesn't know about Method_A
}
:
A* m_A_Ptr ;
} ;
-----------------------------
-----------------------------
This can be corrected by changing the B.H file and adding a B.CPP like so:
-----------------------------
-----------------------------
header file B:

#include "A.h" ; // change declaration to included A.h

class B
{
void Method_B() ; // declaration only
:
A* m_A_Ptr ;
} ;
------------------------------
CPP file B:

#include "B.h" ;

ClassB::Method_B()
{
m_A_Ptr->Method_A( ) ; // no error
}
-----------------------------
-----------------------------

Note that B.CPP gets its definition of class A from the include of A.h in
B.h.

Also, it is STRONGLY recommended you place a "#pragma once" at the top of
each .H file (but never in a .CPP file) which means if it occurs more than
once in a definition the compiler will ignore all but one include of this
header file. That way you can have more than one .H file included in the
same definition, all of which have a common .H included (e.g., program
equates/defines header), file without problems...

[==P==]