TweetFollow Us on Twitter

C++ Methods, Fortran
Volume Number:7
Issue Number:2
Column Tag:Jörg's Folder

Related Info: Quickdraw

C++ Methods In FORTRAN

By Jörg Langowski, Editorial Board

“C++ Methods in FORTRAN”

This article had to come. Next thing you’ll see, you may think, is calling Eiffel from Forth. But seriously, implementing cross-language calling very often helps you to understand how one particular language really works and how to get most out of it. Also, the Fortran run time system has some advantages, like well-designed console I/O that may help in debugging, file I/O, an easily accessible output window, and therefore adding it may be very helpful in some applications. So here we go, and write a C++ method in Language Systems Fortran.

C++ methods are really independent subroutines, and the association between a method and its class is done through the header file - on the source code side - and through the modified method name on the object code side. When you define two different classes with methods of the same name, as in

// 1

class aaa {
 public:
 void doit();
}

class bbbb {
 public:
 void doit();
}

the methods are usually defined in a place different from where they are actually used. In fact, most often they may be pre-compiled in a library. The linker can distinguish between the two different doit methods, because their symbolic name on the linker level is modified by the class name. The two methods’ names in this case would be: doit__3aaaFv and doit__4bbbbFv.

C++ Function Name Encoding

To remind you of the C++ linker naming conventions: the first part of the linker name is the method name (doit), followed by two underscores. Then follows the class name, preceded by the number of characters in that name. Appended to that are some symbols describing the parameter list. In our case, for methods taking no parameters, it is simply “Fv”. F stands for a function, v for a void parameter list. I am not describing all the modifiers that are used in creating a linker name out of a C++ method name; the full encoding scheme is described in the AT&T C++ release notes, chapter 6, page 22.

Usually, you never see the encoded names; only when e.g. a method is defined in a class header file, then referenced by some code using objects from that class, but never actually implemented, the linker might complain about a missing function. There, you will probably have seen those funny names already, and used the MPW unmangle tool to make sense out of them.

Here, we want to go the other direction. When we implement a C++ method in some non-object language, we must write a routine that has the encoded method’s name. The easiest way to find out about the linker name of a C++ method is not to construct it yourself (you never get it right in the first place), but just to define the method in the class header, use it in the code, and never actually implement it. The linker will tell you in its error message what function it is looking for.

That way I found out that the name for the method pascal void FtnCall() in the class TMacTutorDocument is FTNCALL__17TMACTUTORDOCUMENT. The characters “Fv” are not appended here, and the name is written in all capitals, because of the “pascal” keyword. This also means that all external Pascal-type methods of the same name in the same class will have the same linker name, regardless of the argument list.

Language Systems Fortran, of course, uses Pascal calling conventions, so a method written in Fortran will have to be defined in C++ as pascal. We want to pass some parameters, so lets define an argument list:

{2}

pascal void FtnCall(short *menuitem, long k, float *r);

The method will later be called from a menu handler, just for the fun of it, and we pass the number of the menu item selected, and some numbers. Note one restriction here: LS Fortran symbolic names are limited to 31 characters, so don’t use too complicated class and method names if you don’t want to run out of space.

The Sample Program

We use the sample program that I showed you in V6#1: Apple’s C++ mini-application skeleton. You should now go back to your library and get that MacTutor issue, or reorder it, because we obviously cannot reprint its full source here. Listing 2 only shows those parts that have been changed.

In the constructor and destructor methods of the application class we have added calls to InitFortran() and ExitFortran() for initializing the Fortran run time system at the start of the program and leaving it properly at the end. During the program, then, the run time system is at our disposal. The Fortran method is defined in the class TMacTutorDocument. It is used in the TMacTutorApp class, in its DoMenuCommand method:

// 3

x = 4.567;
fMacTutorCurDoc->FtnCall(&menuItem,3456,&x);

This way we have some calls by reference (standard Fortran calling convention), and one call by value.

The Fortran routine (listing 1) receives the three parameters in the same order. Furthermore, on every method call a handle to the method’s current object (this) is pushed on the stack after all the method’s parameters. The Fortran code has to take that extra parameter into account. Thus, the first line of the Fortran routine will be

C 4

subroutine FTNCALL__17TMACTUTORDOCUMENT
 (menuitem,%val(k),r,%val(this))  .

menuitem and r are passed by reference, k is received by value (Language Systems Fortran has an option for receiving parameters by value in the subroutine definition). this is also received by value. Through this, we can access the instance variables of the method’s current object. We also define the list of instance variables, which becomes rather complicated as we have to dereference handles in the (Languages Systems) Fortran way. The structure definitions at the beginning of the Fortran routine show you how to do that.

this points to the beginning of the object’s instance variables, starting with those of the topmost ancestor class and descending through the class hierarchy. In our case, we have a window pointer fDocWindow and the pointer to the virtual methods table vptr from the TDocument class, then the instance variables of TMacTutorDocument, fItemSelected and fDisplayString.

The main body of the routine displays the passed parameters and some information about the instance variables in the Fortran output window.

That’s all! You’re now able to add Fortran code to C++ programs as you like, and have it behave like real C++ methods.

Listing 1: C++ method written in Fortran

CC++ test method written in Language Systems Fortran
CFor editing, some of the lines had to be split. I have not
Ccreated proper Fortran continuation lines, because a. C I’m lazy and 
b. I think the text can be read better that 
Cway -- jl --

 subroutine FTNCALL__17TMACTUTORDOCUMENT
 (menuitem,%val(k),r,%val(this))
Cpascal void FtnCall__17TMacTutorDocument
 (short *menuitem, long k, float *r, 
 struct TMacTutorDocument **);
 include “Quickdraw.f”

 structure /MTDocVars/
 record /WindowPtr/ fDocWindow
 integer*4 vptr
 integer*2 fItemSelected
 record /StringPtr/ fDisplayString
 end structure
 
 structure /MTDocPtr/
 pointer /MTDocVars/ p
 end structure
 
 structure /MTDocHdl/
 pointer /MTDocPtr/ h
 end structure
 
 record /MTDocHdl/ this
 
 integer*2 menuitem

 integer top,left,bottom,right
 
 call MoveOutWindow (20,260,490,340)
 write (*,*) “Arguments to FtnCall:”,menuitem,k,r
 write (*,*) “fItemSelected = “,this.h^.p^.fItemSelected
 write (*,*) “fDisplayString = 
 “,this.h^.p^.fDisplayString.sptr^
 
 top    = this.h^.p^.fdocwindow.wp^.portrect.top
 bottom = this.h^.p^.fdocwindow.wp^.portrect.bottom
 left   = this.h^.p^.fdocwindow.wp^.portrect.left
 right  = this.h^.p^.fdocwindow.wp^.portrect.right
 write (*,*) “doc window = “,top,left,bottom,right
 return
 end
Listing 2: Changes to the .cp and .h files from the V6#1 example

File MacTutorApp.make:

OBJECTS = TApplication.cp.o TDocument.cp.o 
 MacTutorApp.cp.o MacTutorDoc.cp.o 
 MacTutorGrow.cp.o FtnCall.f.o
HEADERS = MacTutorApp.h MacTutorDoc.h 
 MacTutorGrow.h

TApplication.cp.o ƒ TApplication.cp TApplication.h
  CPlus  TApplication.cp
TDocument.cp.o ƒ TDocument.cp TDocument.h
  CPlus  TDocument.cp
MacTutorApp.cp.o ƒ MacTutorApp.make 
 {HEADERS} MacTutorApp.cp
  CPlus  MacTutorApp.cp
MacTutorDoc.cp.o ƒ MacTutorApp.make 
 {HEADERS} MacTutorDoc.cp
  CPlus  MacTutorDoc.cp
MacTutorGrow.cp.o ƒ MacTutorApp.make 
 {HEADERS} MacTutorGrow.cp
  CPlus  MacTutorGrow.cp
FtnCall.f.o ƒ MacTutorApp.make FtnCall.f
  Fortran -mc68020 -mc68881 -opt=3 -bkg=0 FtnCall.f

MacTutorApp ƒƒ MacTutorApp.make {OBJECTS}
 Link -w -t APPL -c JLMT 
 “{CLibraries}”CRuntime.o 
 {OBJECTS} 
 “{Libraries}”Interface.o 
 “{CLibraries}”StdCLib.o 
 “{CLibraries}”CSANELib.o 
 “{CLibraries}”Math.o 
 “{CLibraries}”CInterface.o 
 “{CLibraries}”CPlusLib.o 
 #”{CLibraries}”Complex.o 
 “{FLibraries}FORTRANLib.o” 
 -o MacTutorApp

MacTutorApp ƒƒ MacTutorApp.make MacTutorApp.r
 Rez MacTutorApp.r -append -o MacTutorApp

File MacTutorApp.h:

class TMacTutorApp : public TApplication {
public:
 TMacTutorApp(void); // Our constructor
 ~TMacTutorApp(void);
 // need a destructor to call EXITFORTRAN

private:
 // routines from TApplication we are overriding
 long HeapNeeded(void);
 unsigned long SleepVal(void);
 void AdjustMenus(void);
 void DoMenuCommand
 (short menuID, short menuItem);

 // routines for our own devious purposes
 void DoNew(void);
 void Terminate(void);
};

File MacTutorDoc.h:

class TMacTutorDocument : public TDocument {
  protected:
 short fItemSelected;
 // string corresponding to menu item selected
 StringPtr fDisplayString;

 void DrawWindow(void);

  public:
 TMacTutorDocument(short resID, StringPtr s);
 ~TMacTutorDocument(void); 
 // routine to access private variables
 void SetDisplayString (StringPtr s) {fDisplayString = s;}
 short GetItemSelected(void) {return fItemSelected;}
 void SetItemSelected(short item) {fItemSelected = item;}

 // methods from TDocument we override
 void DoUpdate(void);
 
 // Fortran calling;
 pascal void FtnCall(short *menuitem, long k, float *r);
};

File MacTutorApp.cp:

pascal void initFortran();
pascal void exitFortran();

// Methods for our application class
TMacTutorApp::TMacTutorApp(void)
{
 Handle menuBar;

 initFortran(); // initialize Fortran runtime system
 
 // read menus into menu bar
 menuBar = GetNewMBar(rMenuBar);
 // install menus
 SetMenuBar(menuBar);
 DisposHandle(menuBar);
 // add DA names to Apple menu
 AddResMenu(GetMHandle(mApple), ‘DRVR’);
 DrawMenuBar();

 // create empty mouse region
 fMouseRgn = NewRgn();
 // create a single empty document
 DoNew();
}

TMacTutorApp::~TMacTutorApp(void)
{
 exitFortran(); // exit Fortran runtime system
}

void TMacTutorApp::DoMenuCommand
 (short menuID, short menuItem)
{
 short  itemHit;
 Str255 daName;
 short  daRefNum;
 float  x;// for testing the Fortran call
 WindowPtrwindow;
 TMacTutorDocument* fMacTutorCurDoc =
 (TMacTutorDocument*) fCurDoc;

 window = FrontWindow();
 switch ( menuID ) {
 case mApple:
 switch ( menuItem ) {
 case iAbout:    // About box
 itemHit = Alert(rAboutAlert, nil);
 break;
 default: // DAs etc.
 GetItem(GetMHandle(mApple), menuItem, daName);
 daRefNum = OpenDeskAcc(daName);
 break;
   }
 break;
 case mFile:
 switch ( menuItem ) {
 case iNew:
 DoNew();
 break;
 case iClose:
 if (fMacTutorCurDoc != nil) {
 fDocList->RemoveDoc(fMacTutorCurDoc);
 delete fMacTutorCurDoc;
   }
 else CloseDeskAcc(((WindowPeek) 
 fWhichWindow)->windowKind);
 break;
 case iQuit:
 Terminate();
 break;
   }
 break;
 case mEdit: // SystemEdit for DA editing & MultiFinder 
 if ( !SystemEdit(menuItem-1) ) {
 switch ( menuItem ) {
 case iCut:
 break;
 case iCopy:
 break;
 case iPaste:
 break;
 case iClear:
 break;
    }
   }
 break;
 case myMenu:
 if (fMacTutorCurDoc != nil) {
 switch ( menuItem ) {
 case item1:
 fMacTutorCurDoc->
 SetDisplayString(“\pC++”);
 break;
 case item2:
 fMacTutorCurDoc->
 SetDisplayString(“\pSample”);
 break;
 case item3:
 fMacTutorCurDoc->
 SetDisplayString(“\pApplication”);
 break;
 case item5:
 fMacTutorCurDoc->SetDisplayString(“\pHave Fun”);
 x = 4.567;
 fMacTutorCurDoc->FtnCall(&menuItem,3456,&x);
 break;
    }
 fMacTutorCurDoc->SetItemSelected(menuItem);
 InvalRect(&(window->portRect));
 fMacTutorCurDoc->DoUpdate();
 }
 break;
   }
 HiliteMenu(0);
} // DoMenuCommand


 

Community Search:
MacTech Search:

Software Updates via MacUpdate

BusyCal 3.7.2 - Powerful calendar app wi...
BusyCal is the powerful, flexible, reliable calendar app for macOS. It's packed with time-saving features and compatible with all leading cloud services including iCloud, Google, Exchange and more.... Read more
BusyContacts 1.4.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
iShowU Instant 1.3.0 - Full-featured scr...
iShowU Instant gives you real-time screen recording like you've never seen before! It is the fastest, most feature-filled real-time screen capture tool from shinywhitebox yet. All of the features you... Read more
Capo 3.8 - Slow down and learn to play y...
Capo lets you slow down your favorite songs so you can hear the notes and learn how they are played. With Capo, you can quickly tab out your songs atop a highly-detailed OpenCL-powered spectrogram... Read more
Viber 11.7.0 - Send messages and make fr...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device, so... Read more
Drive Genius 5.3.1 - $79.00
Drive Genius features a comprehensive Malware Scan. Automate your malware protection. Protect your investment from any threat. The Malware Scan is part of the automated DrivePulse utility. DrivePulse... Read more
CorelDRAW 21.2.0.708 - Graphic design so...
CorelDRAW - professional graphic design software for vector illustration, layout, and so much more. Get started quickly and easily with a wealth of intuitive tools, built-in learning materials,... Read more
Navicat Premium Essentials 12.1.27 - Pro...
Navicat Premium Essentials is a compact version of Navicat which provides basic and necessary features you will need to perform simple administration on a database. It supports the latest features... Read more
OmniFocus 3.4.3 - GTD task manager with...
OmniFocus is an organizer app. It uses projects to organize tasks naturally, and then add tags to organize across projects. Easily enter tasks when you’re on the go, and process them when you have... Read more
Microsoft OneNote 16.30 - Free digital n...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more

Latest Forum Discussions

See All

Breakout: Dark Prison is a fast-paced ac...
Breakout: Dark Prison is an action RPG from LaterSoft. Set in the aftermath of a deadly virus outbreak your daughter has been taken from you because she has an immunity to the illness in her DNA. Not being a fan of experimentation on children –... | Read more »
Apple Arcade in review
This weekend, Apple Arcade will officially be one month old. That means anyone who signed up for the free trial on day one has a decision to make: Stick with the service and shell out $5 a month, or cancel and go about your merry way. | Read more »
Alluris is a choose-your-own adventure g...
Alluris is an RPG that the developer's are calling a swipe-your-own adventure game. This is because the game incorporates a Reigns-style - swiping left or right - selection mechanic to make all the decisions you'd usually expect to make across... | Read more »
Hello Hero All Stars receives update wit...
The first Hello Hero game hit global platforms in 2013 and proved a huge success, with developer Fincon adding two more entries to this popular series of casual RPG games since. Released in June this year, Hello Hero All Stars brings many of the... | Read more »
Zombieland: Double Tapper, a cartoon idl...
Zombieland: Double Tapper is the idle RPG tie-in to the upcoming Zombieland: Double Tap. Oddly, it's one of two different Zombieland games launching today, with the other being the Switch title Zombieland: Double Tap - Road Trip. [Read more] | Read more »
Rusty Lake's The White Door launche...
Rusty Lake and Second Maze's intriguing point-and-click adventure game, The White Door, is now up for pre-order on the App Store. This one sees you playing as Robert Hill, a mental health patient who is suffering from severe memory loss. The game... | Read more »
Hellrule is an auto-runner inspired by G...
Hellrule is an upcoming auto-runner game from independent developer Pedrocorp where players will take control of a dapperly dressed gentlemen who comes equipped with a razor-sharp umbrella for slicing up his foes. The game will be available for... | Read more »
Grobo is a gravity bending puzzle platfo...
Grobo is a 2D puzzle platformer that marks the first release from developers Hot Chocolate Games. You'll find yourself manipulating gravity as you make your through this title that's available now for iOS and Android. [Read more] | Read more »
Adrenaline, Compulsive Entertainment’s h...
Compulsive Entertainment’s high-octane arcade racer, Adrenaline, has now made its way to the App Store following a successful launch on Google Play. It’s a ton of challenging, fast-paced fun, boasting easy-to-learn controls and a varied selection... | Read more »
Mario Kart Tour is adding Super Mario Ga...
Earlier today on Twitter, Nintendo announced that Mario Kart Tour is getting a new racer and track. Fans of Super Mario Galaxy will be pleased to hear that Rosalina is the first post-launch character being added, while the iconic Rainbow Road is... | Read more »

Price Scanner via MacPrices.net

11″ WiFi iPad Pros on sale today for up to $2...
Amazon has new 2018 Apple 11″ WiFi iPad Pros in stock today and on sale for up to $250 off Apple’s MSRP. These are the same iPad Pros sold by Apple in its retail and online stores. Be sure to select... Read more
Apple offers clearance 2018 15″ 6-Core MacBoo...
Apple has clearance 2018 15″ 6-Core Touch Bar MacBook Pros, Certified Refurbished, available starting at only $1999. Each model features a new outer case, shipping is free, and an Apple 1-year... Read more
Apple continues to offer refurbished 2019 21″...
Apple has Certified Refurbished 2019 21″ & 27″ iMacs available starting at $929 and up to $350 off the cost of new models. Apple’s one-year warranty is standard, shipping is free, and each iMac... Read more
Verizon offers free iPhone 7 for customers wh...
Verizon is offering a free 32GB iPhone 7 for new or existing customers who open a new line of service, no trade-in required. Cost of the phone is credited to your account monthly for 24 months. The... Read more
13″ 2.4GHz 4-Core MacBook Pros remain availab...
Apple has a full line of Certified Refurbished 2019 13″ 2.4GHz 4-Core Touch Bar MacBook Pros available starting at $1529 and up to $300 off MSRP. Apple’s one-year warranty is included, shipping is... Read more
Lease one iPhone Xs, Xr, or X at Sprint and g...
Purchase an Apple iPhone X, Xr, Xs, or Xs Max at Sprint, and get a 64GB iPhone Xr for free. Requires 2 new lines or 1 upgrade-eligible line and 1 new line. The fine print: “iPhone Xs (64 GB) $37.50/... Read more
How to use your Apple Education discount to s...
Purchase a new MacBook Pro or MacBook Air using Apple’s Education discount, and take up to $200 off MSRP. All teachers, students, and staff of any educational institution with a .edu email address... Read more
Base 2019 13″ 1.4GHz 4-Core MacBook Pro on sa...
Amazon has the new 2019 13″ 1.4GHz/128GB 4-Core Space Gray Touch Bar MacBook Pro on sale for $100 off Apple’s MSRP. This is the same MacBook Pro sold by Apple in its retail and online stores: – 2019... Read more
Save up to $30 on Apple’s AirPods at these re...
Amazon is offering discounts on new 2019 Apple AirPods ranging up to $30 off MSRP. Shipping is free: – AirPods with Charging Case: $144 $15 off MSRP – AirPods with Wireless Charging Case: $169 $30... Read more
Save $15 on Apple Watch Series 5 models on Wa...
Walmart has new Apple Watch Series 5 models on sale for $15 off Apple’s MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only... Read more

Jobs Board

*Apple* Mobile App Developer - eiWorkflow So...
…eiWorkflow Solutions, LLC is currently looking for a consultant for the following role. Apple Mobile App Developer Tasks the role will be performing: ? Mobile App Read more
Essbase Developer - *Apple* - Theorem, LLC...
Job Summary Apple is seeking an experienced, detail-minded Essbase developer to join our worldwide business development and strategy team. If you are someone who Read more
Best Buy *Apple* Computing Master - Best Bu...
**738230BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Location Number:** 000233-Almeda-Store **Job Description:** The Core Read more
Best Buy *Apple* Computing Master - Best Bu...
**738182BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 000036-Independence MO-Store **Job Description:** **What Read more
*Apple* Mobility Pro - Best Buy (United Stat...
**741450BR** **Job Title:** Apple Mobility Pro **Job Category:** Store Associates **Location Number:** 000168-Mentor-Store **Job Description:** At Best Buy, our Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.