[frontend_server] Plug leaks caused by saving the first compilation result
The first compilation result is leaked in two ways:
1) Directly by saving the component in a variable; and
2) Via an unfortunate context thing, probably a variation of
http://dartbug.com/36983. I will update that bug with a reproduction
example later.
The reason this creates a (big) leak is illustrated with an example:
* Say the first component (A) has 10 libraries in it. Each of these
libraries has parent pointers and points (currently) to A, which again
points to all of the 10 libraries.
* We then do a recompilation, say 5 libraries are reused and 5 are new.
They are put into a component (B). We really should have 10 libraries,
the 5 old ones and the 5 new ones (and for simplicity lets say these are
the ones in B). Notice that the 5 old ones will have their parent
pointers updated and also still be in the list of libraries in A.
We keep 15 libraries alive because we have the 10 original ones saved via
A and the 10 (where 5 is new) saved via B.
* We then do a recompilation, say 2 of the same libraries as was also
recompiled before, these end up in compnent C which has 5 libraries from A,
3 libraries from B and the 2 new ones. All of these libraries will have
their parent pointers updated to point to C.
* Because we saved A we keep all the 10 libraries in A though.
Because we saved A and some of the libraries in A had parent pointers
updated to point to B we also keep B and all libraries in B.
Because we keep B and some of the libraries in B had parent pointers
updated to point to C we also keep C and all libraries in C.
So instead of only having the 10 "live" libraries, we have 10 + 5 + 2 = 17
libraries, a leak of 7. With more compilations this keeps happening and
the leak keeps growing.
This CL stops the leak by not holding on to A (which, in turn, stops holding
on to B etc.)
Change-Id: If4f8b1e240b7c39f084df9cb2690570ff26fa9b3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/149280
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
https://dart.googlesource.com/sdk/+/86f3fde23fac9684f99200841f95db60bab79d20
1 file changed
