• bearophile (7/9) Jan 03 2009 I have seen this:
• Jason House (28/46) Jan 04 2009 Based on what I see in the docs for core.memory, I'd envision something ...

bearophile <bearophileHUGS lycos.com> writes:

I have seen this:
http://dobbscodetalk.com/index.php?option=com_content&task=view&id=966

Walter (from a comment written by someone else):

A critical program, such as life support machines, flight control  systems,
etc., cannot be allowed to fail.<

Such software most probably works with a fixed amount of memory (or at compile
time it's known the maximum amount of memory required), so that's not an
example where recovering from out-of-bound errors is important.


The memory manager can have user supplied callbacks to release memory in such
cases.<

This is interesting. What's a possible API/semantics for such thing?

Bye,
bearophile

Jason House <jason.james.house gmail.com> writes:

bearophile wrote:

 I have seen this:
 http://dobbscodetalk.com/index.php?option=com_content&task=view&id=966
 
 Walter (from a comment written by someone else):
 
A critical program, such as life support machines, flight control 
systems, etc., cannot be allowed to fail.<

 
 Such software most probably works with a fixed amount of memory (or at
 compile time it's known the maximum amount of memory required), so that's
 not an example where recovering from out-of-bound errors is important.

That's a good point :)


The memory manager can have user supplied callbacks to release memory in
such cases.<

 
 This is interesting. What's a possible API/semantics for such thing?

Based on what I see in the docs for core.memory, I'd envision something like
the following:

// Sample allocation logic
void* allocate(int nBytes){
  void* result = null;
  if (tryAllocate(nBytes, &result))
    return result;
  onSoftOutOfMemory();
  if (tryAllocate(nBytes, &result))
    return result;
  onHardOutOfMemory();
}

// Default handlers for out of memory
void onSoftOutOfMemory(){
  foreach(callback; registeredOutOfMemoryHandlers)
    callback();
  GC.collect();
}
void onHardOutOfMemory(){
  abort(-1);
}

// Exposed functions to use this new functionality
void addOutOfMemoryHandler(void function () callback);
void addOutOfMemoryHandler(void delegate () callback);
void removeOutOfMemoryHandler(void function () callback);
void removeOutOfMemoryHandler(void delegate () callback);  


Theoretically, onHardOutOfMemory could be replaced with a version that throws
for those who believe they can't live without it.



 
 Bye,
 bearophile