Writing a shared library - ASM Help

[nyteschayde]

So I have been following this guide to create a shared library in C for the Amiga. So far the default example works fine. The questions I have, as I want to adopt my code for the library, are these:

• How do the registers work? What's the difference between A0/A1/D0 etc...?
• What happens if I have more than one argument? Which registers do I use?
• What about var args?
• Does anybody know how this would differ if done in GCC? Can I, do I have to, link the SAS/C libinit.o/libinitr.o files?

I want to not only post the library I am building, but I want to be able to quickly reuse it for my own applications as I write them. Anybody else do this? Any fun stuff to share?

[nyteschayde]

So it seems that A[0-7] is for addresses and D[0-7?] is for data? I am still not quite sure which parameters to associate with which registers. I am guessing that anything that is a not a pointer would get D register and all pointers an A register? However, that is purely a guess.

[nyteschayde]

Answering my previous question, any argument that is a pointer to something goes in an __a register and anything that is a direct value goes in a __d register. It appears there are roughly 7 usable pointer registers and perhaps 7-8 direct value registers per function definition.

Code: [Select]

void __saveds __asm someFunction(
  register __a0 APTR ptr1,
  register __a0 APTR ptr1,
  register __a1 APTR ptr2,
  register __a2 APTR ptr3,
  register __a3 APTR ptr4,
  register __a4 APTR ptr5,
  register __a5 APTR ptr6,
  register __a6 APTR ptr7,
/*register __a7 APTR ptr8,      Seems this one is special */
  register __d0 BPTR val1,
  register __d1 BPTR val2,
  register __d2 BPTR val3,
  register __d3 BPTR val4,
  register __d4 BPTR val5,
  register __d5 BPTR val6,
  register __d6 BPTR val7,
  register __d7 BPTR val8
);

Alright folks, I have this all working fairly well. I have now run into another issue that I am not sure how to fix and I cannot, as of yet, find any docs around. When making the shared library you typically have to tag and define the functions that the library will use with register designations. But I am not sure what to do for varargs style functions

Code: [Select]

/* Typical Example */

struct Person {
  STRPTR name;
  SHORT age;
};

int __saveds __asm getAge(register __a0 struct Person *p) {
  return p->age;
}

/** Varargs?! */

int * __saveds __asm getAges(register __a0 struct Person *first, ...) {
  /* Loop through and collect the ages and return as int array */
}


Does the ... need to be tagged with a register?