[B2-devel] Memory mapping

[<ni...@in...>]

1) Mac OS X mmap() doesn't work.
   It always sets errno=ENOTSUP - Not Supported.
   I may be able to use a Mach primitive in the future,
   but for now, REAL_ADDRESSING is out of the question.

2) main_unix.cpp currently does this for DIRECT_ADDRESSING:

	// Create areas for Mac RAM and ROM
#if REAL_ADDRESSING || DIRECT_ADDRESSING
...
	{
		RAMBaseHost = (uint8 *)mmap(0, mapped_ram_rom_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, zero_fd, 0);
		if (RAMBaseHost == (uint8 *)MAP_FAILED) {
			ErrorAlert(GetString(STR_NO_MEM_ERR));
			QuitEmulator();
		}
		ROMBaseHost = RAMBaseHost + aligned_ram_size;
	}
#else
	RAMBaseHost = (uint8 *)malloc(RAMSize);
	ROMBaseHost = (uint8 *)malloc(0x100000);
	if (RAMBaseHost == NULL || ROMBaseHost == NULL) {
		ErrorAlert(GetString(STR_NO_MEM_ERR));
		QuitEmulator();
	}
#endif



   Now, because mmap() always fails, direct addressing also seems
   out of the question. But, my question is, why can't we just do
   a malloc() in this case?

   What is this mmap() actually doing, apart from allocating memory?

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