Re: fix memory leak in gengtype

[Jeff Law <law at redhat dot com>]

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On 04/20/11 15:08, Dimitrios Apostolou wrote:
> Hello list,
> 
> while trying to build gcc-4.6.0 on my sparcstation, I got gengtype OOM
> killed. That's when I noticed that its RAM usage peaks at 150MB, which
> is a bit excessive for parsing a ~500K text file.
> 
> The attached patch fixes the leak and gengtype now uses a peak of 4MB
> heap. Hopefully I don't do something wrong, since it took me a while to
> understand those obstacks...
The code in question creates an obstack, allocates (and grows) a single
object on the obstack, then frees the object.  This leaks the underlying
obstack structure itself and potentially any chunks that were too small
to hold the object.

It turns out there's a similar leak in gengtype.c which is fixed in the
same way.

A quick valgrind test shows that prior to your change gengtype leaked
roughly 200M, after your change it leaks about 1.3M and after fixing
gengtype it leaks a little under 300k.

I'll run those changes through the usual tests and check in the changes
assuming they pass those tests.

Thanks for the patch!

> 
> P.S. I was trying to test gcc on a rare arch (sparc-unknown-linux-gnu)
> but unfortunately the sparcstation crashed and burned after this, so I
> can't continue the build and report back :-(
:(  My old PA box has similar problems, though it merely overheats
before a bootstrap can complete, so in theory I could coax it to finish
a bootstrap.   Luckily others (particularly John) have stepped in over
the last decade and taken excellent care of the PA port.

Jeff

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