Hi folks,

I'm trying to learn some really simple C but can't seem to get past the very basics.

Trying to follow some simple tutorials, I can't get this to compile:


Quote:

struct Library *OpenLibrary(); struct IntuitionBase *IntuitionBase; int main() { IntuitionBase=(struct IntuitionBase *)OpenLibrary("intuition.library",39); return 0; }

The error is Quote:

undefined reference to `OpenLibrary'

I'm aware this is probably something stupid but would appreciate if anyone can point it out to me.

Cheers

Last edited by Robert on 03-Mar-2018 at 04:13 PM.

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Robert
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@Robert

You are defining a function OpenLibrary() (otherwise it would complain at compiler level), but you fail to implement it or tell the linker where to find it.

A lot can be different depending on which compiler you use, how it is invoked on which version of AOS is the target.

Try replacing that line with:

#include >proto/exec.h>

Edit: Forum doesn't like the left-hand version of ">" so turn the 1st around.....

Last edited by Kronos on 03-Mar-2018 at 03:54 PM.
Last edited by Kronos on 03-Mar-2018 at 03:52 PM.

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@Kronos

Quote:

Kronos wrote: @Robert You are defining a function OpenLibrary() (otherwise it would complain at compiler level), but you fail to implement it or tell the linker where to find it. A lot can be different depending on which compiler you use, how it is invoked on which version of AOS is the target.

Thanks Kronos. The compiler is GCC 4.2.4, it's invoked from shell (e.g. gcc -o test test.c) and the OS is AmigaOS4.1.

Quote:

Try replacing that line with: #include >proto/exec.h> Edit: Forum doesn't like the left-hand version of ">" so turn the 1st around.....

Thanks but still seeing the same error:

undefined reference to `OpenLibrary'

Last edited by Robert on 03-Mar-2018 at 04:14 PM.

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Robert
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@Robert

Hey up. So, I think a problem you are facing is that Libraries in OS4 work rather differently than they did in 3.x.

Depending on how your compiler is configured, you'll want to use something like declaring:

struct IntuitionBase* IntuitionBase = NULL;
struct IntuitionIFace* IIntuition = NULL;

Get the library base:

IntuitionBase = (struct IntuitionBase*)IExec->OpenLibrary(...);

and then obtain the interface for it:

IIntuition = (struct IntuitionIface*) IExec->GetInterface((Library*)IntuitionBase, "main", 1, NULL));

It's a bit more involved. Although I am sure there is some glue logic that allows the code you have written to work as-is.

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I tend to use the following template logic for C++ at least:

template<typename L, typename I>
inline bool openMainLibInterface(L*& library, I*& interface, const char* name, uint32 version)
{
if ( (library = (L*)IExec->OpenLibrary(name, version)) ) {
if ( (interface = (I*)IExec->GetInterface((Library*)library, "main", 1, NULL)) ) {
return true;
}
else {
std::fprintf(stderr, "Opened %s [%p] but failed to get main\n", name, library);
}
}
else {
std::fprintf(stderr, "Failed to open: %s\n", name);
}
return false;
}

template<typename L, typename I>
inline void closeMainLibInterface(L*& library, I*& interface)
{
if (interface) {
IExec->DropInterface((Interface*)interface);
interface = 0;
}
if (library) {
IExec->CloseLibrary((Library*)library);
library = 0;
}
}

So that I can open/close libraries and their main interfaces easily.

struct IntuitionBase* IntuitionBase = 0;
struct IntuitionIFace* IIntuition = 0;

if (openMainLibInterface(IntuitionBase, IIntuition, "intuition.library")) {
...
}

Also, I forgot how to post indentible in xoops lol.

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@Robert

Actually, I think that is a linker error. If it were the compiler, it would say something like

Quote:

error: implicit declaration of function 'OpenLibrary'

You probably need to compile with something like

Quote:

gcc -o test test.c -lfoo

where 'foo' is the name of the library.

I know how to find library names on Linux, not not on AmigaOS 4.x -- perhaps someone else can add this information.

Update: or maybe not. Take a look at this:

http://wiki.amigaos.net/wiki/The_Hacking_Way:_Part_1_-_First_Steps#Myth_.231:_AmigaOS_behaves_like_UNIX

Last edited by bison on 03-Mar-2018 at 04:55 PM.

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@Karlos

Hey Karlos! Long time no' speak, etc. Hope you're well, sir.

Anyway, back to the issue at hand, that's helped at least as far as getting rid of the error.
Thanks.

_________________
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A1XE G4, OS4.1. Peg1 G3, MOS 1.4.
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@Robert

Quote:

Trying to follow some simple tutorials, I can't get this to compile:

Well the tutorial is wrong, maybe not so good idea to learn how to code from some one who is clueless.
Quote:

struct Library *OpenLibrary();

I not sure what your trying to do here?
It is 110% wrong.

you need includes on top file.

#include "proto/exec.h"
#include "proto/dos.h"
#include "proto/IIntuition.h"

should " should be greater or smaller but breaks.

you should compile with:

gcc source.c -o your_program_name -D__USE_INLINE__

"-D__USE_INLINE__" allows you drop "IEXEC->" from OpenLibrary, or else it is.

DOSBase = IExec->OpenLibrary("dos.library",50);

Next you need to Obtain a Interface before you call any function inside the library..
(this only AmigaOS4.1)

See the AmigaOS4.1 SDK autodocs for Exec.library
It in the SDK:Documentation/Autodocs directory.

Last edited by NutsAboutAmiga on 03-Mar-2018 at 05:10 PM.
Last edited by NutsAboutAmiga on 03-Mar-2018 at 05:08 PM.
Last edited by NutsAboutAmiga on 03-Mar-2018 at 05:02 PM.
Last edited by NutsAboutAmiga on 03-Mar-2018 at 04:59 PM.

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@NutsAboutAmiga

Quote:

NutsAboutAmiga wrote: Well the tutorial is wrong, maybe not so good idea to learn how code from some who is clueless.

It's from here:
http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node0578.html

If anyone knows a decent resource for OS4-specific beginner tutorials, that would be appreciated.

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Abel Soul - Check out our tunes on Spotify

@Robert

Have look here:

http://wiki.amigaos.net/wiki/Tutorials:Main

This one nice to start with, learn what this does.

http://wiki.amigaos.net/wiki/Programming_AmigaOS_4:_Exec_-_The_Kernel

Last edited by NutsAboutAmiga on 03-Mar-2018 at 05:13 PM.

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@Robert

/* easy.c: a complete example of how to open an Amiga function library in
 * C. In this case the function library is Intuition.  Once the Intuition
 * function library is open, any Intuition function can be called.  This
 * example uses the DisplayBeep() function of Intuition to flash the
 * screen With SAS/C (Lattice), compile with lc -L easy.c
 */

/* Declare the return type of the functions we will use.                 */
struct Library *OpenLibrary();  /* These Exec library functions can be   */
void            CloseLibrary(); /* called anytime (Exec is always open). */

void            DisplayBeep();  /* Before using this Intuition function, */
                                /* the Intuition library must be opened  */

struct IntuitionBase *IntuitionBase; /* Get storage for the library base */
                                     /* The base name MUST be            */
                                     /* IntuitionBase                    */

int main()
{
    IntuitionBase=(struct IntuitionBase *)
                  OpenLibrary("intuition.library",33L);

    if(IntuitionBase)           /* Check to see if it actually opened.   */
        {                       /* The Intuition library is now open so  */

        DisplayBeep(0L);        /* any of its functions may be used.     */

        CloseLibrary(IntuitionBase); /* Always close a library if not    */
                                     /* in use.                          */


   
you need to close the interface after obtaining a interface.



        }
    else                        /* The library did not open so return an */
       {                        /* error code.  The exit() function is   */
       exit(20);                /* not part of the OS, it is part of the */
       }                        /* compiler link library.                */
}

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@NutsAboutAmiga

Quote:

NutsAboutAmiga wrote: @Robert Have look here: http://wiki.amigaos.net/wiki/Tutorials:Main This one nice to start with, learn what this does. http://wiki.amigaos.net/wiki/Programming_AmigaOS_4:_Exec_-_The_Kernel

Thanks very much, I'll check that out.

Last edited by Robert on 03-Mar-2018 at 05:52 PM.

_________________
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@Robert

Not bad mate. One or two minor changes since we last spoke I guess. Married, two children :D

Hope all is well with yourself.

Last edited by Karlos on 03-Mar-2018 at 08:30 PM.

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@Karlos

Quote:

Karlos wrote: @Robert Not bad mate. One or two minor changes since we last spoke I guess. Married, two children :D

Yes, minor changes indeed!

Belated congratulations on all counts.

Quote:

Hope all is well with yourself.

As well as could be reasonably expected for an auld geek.
Finally finding the odd half hour here and there to play with my Amigas again, which has been a pleasant distraction. Got the A1 and Peg1 up and running again.
Unfortunately the A1200 remains switched off for now as I have been unable to locate the cable that connects it to the 1084s but it still looks nice sitting there.

_________________
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A1XE G4, OS4.1. Peg1 G3, MOS 1.4.
Abel Soul - Check out our tunes on Spotify

@Robert

I don't think that would work on an actual Amiga either. As stated it's missing includes. That's makes a bad example.

@Hypex

Quote:

don't think that would work on an actual Amiga either. As stated it's missing includes. That's makes a bad example.

It doesn't need any includes. All the functions have been declared, so it would build, but it would need linking against a libamiga to get the library call stubs.

It is ofcourse a pretty bad example.

@Robert

Here is how you would do it now

#define __USE_INLINE__

#include <proto/exec.h>
#include <proto/intuition.h>

struct Library *IntuitionBase;
struct IntuitionIFace *IIntuition;

int main(int argc, char *argv[])
{
	if((IntuitionBase = OpenLibrary("intuition.library",0L)))
	{
#if defined (__amigaos4__)
		if((IIntuition = (struct IntuitionIFace *)GetInterface(IntuitionBase, "main",1,0)))
		{
#endif
			DisplayBeep(0L);
			
#if defined  (__amigaos4__)
			DropInterface((struct Interface *)IIntuition);
		}
#endif
		CloseLibrary(IntuitionBase);
	}
}

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@NutsAboutAmiga

Quote:

DisplayBeep(0L) wont work on RTG screen, you wont see any color change on the screen.

Except that it does. It's patched by Iprefs (I think) since quite some time, to play a sound and or flash the title bar.

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@broadblues

I guess that beta or something you have?

I know nothing, not part of inner circle.

Last edited by NutsAboutAmiga on 04-Mar-2018 at 09:02 PM.
Last edited by NutsAboutAmiga on 04-Mar-2018 at 09:00 PM.

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@broadblues (& all)

These replies are excellent, thanks.
I'm already getting a *slightly* better understanding of things.

Cheers.

_________________
Robert
--
A1XE G4, OS4.1. Peg1 G3, MOS 1.4.
Abel Soul - Check out our tunes on Spotify

@NutsAboutAmiga

Quote:

I guess that beta or something you have? I know nothing, not part of inner circle.

Hardly beta, it's been that way since 3.1 and I think even 2.04 but I don't have 2..04 to check on.

If you *don't* see flash or hear a beep, chack your sound prefs settings.

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