Reorganizing the address space

Posted Jul 1, 2004 1:54 UTC (Thu) by ajax (guest, #7251)
Parent article: Reorganizing the address space

> Any application which is sensitive to how virtual memory is
> laid out is buggy to begin with; according to Arjan van de
> Ven, the most common case is applications which store
> pointers in integer variables and then do the wrong thing
> when they see a "negative" value.

Changing the address space layout rules also affects those applications that specify where in the address space their mmaps are to be placed. Changing the rules where the 'holes' are can and usually break such applications.

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Reorganizing the address space

Posted Jul 1, 2004 17:48 UTC (Thu) by vmole (guest, #111) [Link] (1 responses)

Such applications are already broken. There's never been any guarantee that the the specified start address would be honored, and the mmap documentation has always been clear on that.

Reorganizing the address space

Posted Jul 1, 2004 18:56 UTC (Thu) by obobo (guest, #684) [Link]

There's a difference between non-portable and broken. For example, I've used the mmap start address specification to do emulation and testing (on my desktop machine) of a flash filesystem that would run on an embedded device (and that was located at a certain address on that device). While the mmap call wasn't guaranteed to work, it did, and saved me a few weeks of effort re-writing the filesystem.

If this change broke my program (it didn't) I wouldn't have cause to yell too loud; it was not guaranteed to continue to work. But I still wouldn't call the program "broken".

-Bill