#5278: On modern fedora 64 installs, sage exists frequently when omalloc thinks
there is no memory left
---------------------+------------------------------------------------------
Reporter: was | Owner: cwitty
Type: defect | Status: new
Priority: blocker | Milestone: sage-3.3
Component: misc | Resolution:
Keywords: |
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Comment (by GeorgSWeber):
Hi all,
I currently do not have access to Fedora or any Linux system at the
moment, let alone a 64-bit system. But I do have seen some odd queer
things in my past "low level C years" on embedded systems with all sort of
crap architectures and compilers.
My proposals here would be to poke around along the lines of:
- Is "NULL" really what you think here?
- Do we compare against what we want to compare against?
Given a box, I would test certain code alternatives to "if (ptr == NULL)"
as:
{{{
if (ptr == (void *)NULL)
}}}
{{{
if (ptr == (void *)0x0)
}}}
{{{
if ((void* )ptr == (void*)0x0)
}}}
I have seen environments where exactly one version was the one to be
taken. And sometimes one has to read the assembler code to see what a
compiler can wreak havoc to 100% correct ANSI C code ... but I have never
read the GNU assembler language docs.
As far as "hackish" concerns, I think I can do worse than the above code:
{{{
do {;} while(NULL == (ptr = OM_MALLOC_FROM_SYSTEM(size)));
}}}
But seriously, from what I see perhaps all we need is to start some sort
of timer in the "OM_MEMORY_LOW_HOOK();" to let the system recover from a
situation where it couldn't give us the needed free memory on our first
request. Or some other system-related magic that ensures that --- provided
the memory is avaible at all :-) --- makes sure that the following call
will be successful.
This C code does not seem to me so very hackish, after all, but even
nicely customizable by the obvious hooks and macros.
Yeah, probably it's a good idea to check what the OM_MEMORY_LOW_HOOK()
macro does do right now.
Cheers,gsw
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5278#comment:4>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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