[antlr-interest] Memory management of C target

Jim Idle jimi at temporal-wave.com
Mon Jan 31 09:43:11 PST 2011

The C target will be a lot faster than the Java target, but the objects
that are created are probably bigger. For v4 I plan to reduce that a lot.
It is probably better to reduce the input though. 530,000 lines of C code
as input seems a bit of a tall order for anything, even if you parse it.
The individual input files would be better.

Also, I think you were using $text references in your parser and these
will create hundreds of thousands of string objects that will not be
released until you release the parser. To use the text of an object it is
better to get the pointer to the input from that object and use the length
(start and end pointer are stored in the object) so that you make no
copies or memory allocations. The $text (in the C target) is a convenience
method that is relatively slow and inefficient; it is just there when you
don't really care that much about those factors. This catches so many
people that I may abandon it in v4, in favor of functions/macros that give
you the information.

You can also try 64bit mode, which will raise the 2GB bar.


> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Marco Trudel
> Sent: Monday, January 31, 2011 5:37 AM
> To: antlr-interest at antlr.org
> Subject: [antlr-interest] Memory management of C target
> Dear all
> Does anyone know how the C target handles memory? I noticed that with
> very big input (e.g. 530.000 lines of C code) it crashes because it
> hits the 2gb process memory limit. Is there something I can tweak to
> make it work or do I have to split the input?
> The Java target manages to parse the input if I give the process 1gb.
> It even requires only 20 seconds.
> Would be great if the C target could also do that. Even better it the
> required time would be about half of the one of the Java target (as I'm
> used to when the C target can handle the input).
> Thanks
> Marco
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