Could someone explain __declspec(naked) please?

Question

I'm looking into porting a script engine written for Windows to Linux; it's for Winamp's visualization platform AVS. I'm not sure if it's even possible at the moment. From what I can tell the code is taking the addresses of the C functions nseel_asm_atan and nseel_asm_atan_end and storing them inside a table that it can reference during code execution.

I've looked at MS's documentation, but I'm unsure what __declspec(naked) really does. What is prolog and epilog code mentioned in the documentation? Is that related to Windows calling conventions? Is this portable? Know of any Linux-based examples using similar techniques?

static double (*__atan)(double) = &atan;
__declspec ( naked ) void nseel_asm_atan(void)
{
  FUNC1_ENTER

  *__nextBlock = __atan(*parm_a);

  FUNC_LEAVE
}
__declspec ( naked ) void nseel_asm_atan_end(void) {}

Answer 1

Basically the function prologue sets up a stack frame for local variables and the epilogue takes care of cleaning it up. This is usually done automatically by the compiler. If you use __declspec(naked), setting up this stack frame will be up to you so it gives you more flexibility.

There are many references: here , here, also here and more.

The GNU gcc compiler also supports naked, but apparently not for x86: search for "naked" in the page (I haven't tried to see if it works on x86)