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How to use EmulateTags() call
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I'm trying to use the EmulateTags() function to access a 68K-only library.

I'm getting a crash reported when the following line executes:

BoardInfoPtr = (struct BoardInfo*) EmulateTags((APTR) (BoardsBase - 0x24), ET_RegisterD0, SB_DISABLE_CUSTOMCHECK, TAG_DONE);

The library is already open and its address is in BoardsBase. The function I want to access in this case is AllocBoardInfo() which has an offset of $24.

The 68K version works fine even on OS4 so it seems to be an issue with how I am calling EmulateTags() rather than with boards.library itself. I assume I don't need to use GetInterface() as it's a 68K-only library.


Edited by Minuous on 2013/8/14 21:24:07
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Re: How to use EmulateTags() call
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If you call the library like this, you expect that there never will be a ppc native version of boards.library. Is this what you want? Otherwise you should rather create a boards.l.main and use the ppc native interface.

Regarding EmulateTags, I guess you have to add ET_RegisterA6,BoardsBase.


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Re: How to use EmulateTags() call
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>Regarding EmulateTags, I guess you have to add ET_RegisterA6,BoardsBase.

Still has the same problem even when using that tag...

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Re: How to use EmulateTags() call
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When doing LVO library calls with EmulateTags() you can specify the LVO offset using ET_Offset.

This is from the source code of a xpkmaster.l.main file:
LONG _Xpkmaster_XpkExamine(  
  
struct XpkmasterIFace *Self,
  
struct XpkFib fib,
  
struct TagItem tags)
{
  
struct Library *LibBase Self->Data.LibBase;
  
struct ExecIFace *IExec = (struct ExecIFace *)Self->Data.IExecPrivate;
  
LONG retval;
  
ULONG *regs = (ULONG *)(((struct ExecBase *)(IExec->Data.LibBase))->EmuWS);
  
ULONG save_a6 regs[14];

  
retval = (LONG)IExec->EmulateTags((APTR)LibBase,
    
ET_Offset,     -36,
    
ET_RegisterA0fib,
    
ET_RegisterA1tags,
    
ET_RegisterA6LibBase,
    
TAG_DONE);

  
regs[14] = save_a6;
  return 
retval;
}


You can get the full source here:
http://os4depot.net/index.php?functio ... sc/xpkmaster-gluefile.lha

The "(BoardsBase - 0x24)" you have in your code likely doesn't do what you want because the BoardsBase variable points to a struct Library so you are subtracting 0x24 * sizeof(struct Library) bytes from the pointer rather than just 0x24 bytes. In order to get the result you want you would have to change it to "((uint8 *)BoardsBase - 0x24)".

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Re: How to use EmulateTags() call
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OK, many thanks.

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Re: How to use EmulateTags() call
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Quote:

thomas wrote:

If you call the library like this, you expect that there never will be a ppc native version of boards.library. Is this what you want? Otherwise you should rather create a boards.l.main and use the ppc native interface.


True. However, if you still want to use EmulateTags(), then the best thing to do would be to call IExec->IsNative(funcPtr) first to check if it's native or 68K, and then either call directly, or use EmulateTags().

Hans

http://hdrlab.org.nz/ - Amiga OS 4 projects, programming articles and more.
https://keasigmadelta.com/ - more of my work
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Re: How to use EmulateTags() call
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Actually it should be sufficient to try GetInterface(LibBase,"main"). If it fails, call the 68k functions with EmulateTags and if not, call the functions from the interface.


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