• Alexibu (6/6) Aug 31 2023 Why do I need to copy data out of memory mapped files to avoid
• H. S. Teoh (12/17) Sep 01 2023 No, once you close it, the OS will remove the mapping. So when you try

Alexibu <alex sunopti.com> writes:

Why do I need to copy data out of memory mapped files to avoid 
seg faults.
This defeats the purpose of memory mapped files.
Shouldn't the GC be able to manage it if I keep a pointer into it.
I am closing them because the OS has a limit in how many it can 
open, either way the memory is still there isn't it ?

"H. S. Teoh" <hsteoh qfbox.info> writes:

On Fri, Sep 01, 2023 at 03:53:42AM +0000, Alexibu via Digitalmars-d-learn wrote:
 Why do I need to copy data out of memory mapped files to avoid seg faults.
 This defeats the purpose of memory mapped files.
 Shouldn't the GC be able to manage it if I keep a pointer into it.

The GC does not manage memory-mapped files. That's the job of the OS.


 I am closing them because the OS has a limit in how many it can open,
 either way the memory is still there isn't it ?

No, once you close it, the OS will remove the mapping. So when you try
to access that address, it will segfault.  This has nothing to do with
the GC, the page tables that map the memory addresses to the file are
managed by the OS.  By closing it you're basically telling the OS "I
don't need the mapping anymore", so it removes the mapping from your
page tables and that address no longer exists in your process' address
space.  So the next time you try to access it, you will get a segfault.


T

-- 
Heuristics are bug-ridden by definition. If they didn't have bugs, they'd be
algorithms.