From: "BGB" <cr88192@hotmail.com>
To: "Boehm, Hans" <hans.boehm@hp.com>,
"Andreas Krebbel" <krebbel@linux.vnet.ibm.com>,
"Andrew Haley" <aph@redhat.com>
Cc: <gcc-patches@gcc.gnu.org>, <java@gcc.gnu.org>, <gc@linux.hpl.hp.com>
Subject: Re: libgcj missing symbol __data_start
Date: Wed, 26 Aug 2009 18:25:00 -0000 [thread overview]
Message-ID: <BLU0-SMTP52B3F5E4B11845F4E05891E4F70@phx.gbl> (raw)
In-Reply-To: <238A96A773B3934685A7269CC8A8D042577AC94298@GVW0436EXB.americas.hpqcorp.net>
----- Original Message -----
From: "Boehm, Hans" <hans.boehm@hp.com>
To: "Andreas Krebbel" <krebbel@linux.vnet.ibm.com>; "Andrew Haley"
<aph@redhat.com>
Cc: <gcc-patches@gcc.gnu.org>; <java@gcc.gnu.org>; <gc@linux.hpl.hp.com>
Sent: Wednesday, August 26, 2009 10:41 AM
Subject: RE: libgcj missing symbol __data_start
> [Adding the gc mailing list, since this still applies to current gc
> versions.]
<snip>
<--
Unfortunately, I don't think this is the right solution. If I understand
correctly, DATASTART will end up as zero, which will cause the collector to
start tracing at location zero, which seems unlikely to work, if the value
is needed. I suspect the value isn't actually used when dl_iterate_phdr is
available and the application is dynamically linked, but still ...
Another popular option on other architectures is to define
SEARCH_FOR_DATA_START instead of defining DATASTART to have a specific
value. This creates a weak reference to __data_start. If that ends up
being zero, the collector will walk the address space backwards starting at
__end until an access faults. It will assume that that's the beginning of
the main data segment. That might make debugging a bit harder because of
the extra SIGSEGV at startup, but I still think it's a much better solution,
assuming it actually works. If it doesn't, this at least needs a
conspicuous FIXME comment, since it's pretty clearly doing the wrong thing.
In any case, I think this should also go in the upstream source.
Hans
-->
although not directly related, I will note that for my GC on Windows, I
ended up switching to a strategy of using the ToolHelp library to iterate
over the loaded modules and find their used address ranges...
it also makes the GC work more reliably as well...
I am not sure if something similar can be done on Linux (I have not looked
into this).
next prev parent reply other threads:[~2009-08-26 18:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-25 14:21 Andreas Krebbel
2009-08-25 16:43 ` Andrew Haley
2009-08-26 16:32 ` Andreas Krebbel
2009-08-26 17:42 ` Boehm, Hans
2009-08-26 18:25 ` BGB [this message]
2009-09-01 15:33 ` Andrew Haley
2009-09-02 12:00 ` Andreas Krebbel
2009-09-16 10:32 ` Andrew Haley
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