mmap 是否总是返回更高的地址
mmap（当使用 MAP_ANONYMOUS 调用时，即用于分配内存时）是否总是返回比先前调用更高的内存地址？如果不是这样，有什么办法让它始终返回更高的地址吗？
Does mmap (when called with MAP_ANONYMOUS, that is, for allocating memory) always return higher memory address than a previous call? If not so, Is there any way to make it return a higher address always?
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默认情况下，
mmap可以以任何顺序返回在页面边界上对齐的任何地址。如果您想强制返回的地址是您指定的地址，则可以使用 MAP_FIXED 标志，但这不太便携且可靠。通过这种方式，您可以将代码与特定内核上的
mmap的特定实现联系起来。但无论如何，为什么你总是需要比前一个地址更高的地址呢？可能更好的方法是改变程序的逻辑。
By default,
mmapcan return any address aligned on a page boundary, in any order.If you want to enforce that the returned address is the one you specify, you can use the
MAP_FIXEDflag, but that isn't very portable and reliable. This way you are tying your code with the particular implementation ofmmapon a particular kernel.But anyway, why would you always need a higher address than the previous one? Possibly a better way is to change the logic of your program.
不一定，至少根据它的定义不是。
我相信，使用 ASLR 可能会发生高地址不再可用的情况，因此
mmap必须选择一些较低的地址范围。显然，在 32 位处理器（和内核）上，内存空间可能几乎被填满，因此当要求一个大的
mmap范围时，内核应该找到一个合适的，并且可以在任何地方。如果你想要一个单调的方向，请使用 sbrk （但我真的建议不要使用它）。
另一种可能性是在程序初始化时使用
mmap和MAP_NORESERVE预先分配大量（例如几 TB）的地址空间，并调用mmapcode> 与 MAP_FIXED 再次在该范围内以获得真正可用的空间（在更易于管理的块中，例如几十兆字节）。@MetallicPriest：你真的应该激励并解释更多你的问题。这些问题是如此神秘和奇怪（甚至我无法猜出所有上下文），以至于回答它们并不是很有趣。
Not necessarily, at least not according to its definition.
And I would believe that with ASLR it could happen that upper addresses are no more available, so
mmaphas to choose some lower address range.Obviously, on 32 bits processors (& kernels) the memory space could be nearly filled, so when asking for a big
mmap-ed range the kernel should find one which fits, and that could be anywhere.If you want a monotone direction, use sbrk (but I really recommend against using it).
Another possibility could be to pre-allocate a very large amount (e.g. several terabytes) of address space using
mmapwithMAP_NORESERVEat program initialization, and callmmapwithMAP_FIXEDinside that range again to get the really usable space (in more manageable chunks, e.g. dozens of megabytes).@MetallicPriest: you really should motivate and explain much more your questions. There are so mysterious and weird (and even I cannot guess all the context) that it is not very fun to answer them.