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Subject: Is the Ada run-time required to detect out-of-memory conditions?
From: Ludovic Brenta <ludovic.brenta@insalien.org>
Date: Fri, 21 May 2004 00:54:27 +0200
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Date: 2004-05-21T00:53:17+02:00
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Hello,

I have received a bug report [1] against GNAT 3.15p and reproduced the
same behaviour with GCC 3.4.  I would like the advice of language
lawyers on the issue.

[1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=250076

The program allocates memory in an infinite loop using "new" and the
default storage pool, and of course exhausts all available storage.
The issue is whether or not Storage_Error should be raised.  With
GNAT, no exception is raised; instead the program receives SIGKILL
(not even SIGSEGV) from Linux.

My first impression is that the program exhausts physical memory (RAM
+ swap) before exhausting the default storage pool, the size of which
is defined to be the total size of the virtual address space.  As a
result, the kernel detects the out-of-memory condition before the Ada
run-time library does, and sends SIGKILL to the program.  Of course,
the program has no chance to turn SIGKILL into an exception.

Is my assessment correct?  Is this a bug in the GNAT library?

Thanks for any insight.

PS. The original reported says that the program receives SIGSEGV.  He
uses Linux 2.4.22.  I use 2.4.26 and the program receives SIGKILL
instead.  I don't know if this is a known change in the kernel's
behaviour.

-- 
Ludovic Brenta.