On 2014-10-07 17:57, Dmitry Olshansky wrote:
I made a proposal to quantatively measure and tabulate all GC
allocations in Phobos before coming up with solutions to "@nogc Phobos".
After approving node from Andrei I've come up with a piece of automation
to extract this data and post it on wiki.
So here is the exhustive list of everything calling into GC in Phobos
(-vgc compiler flag):
http://wiki.dlang.org/Stuff_in_Phobos_That_Generates_Garbage
Including source links, a wild guess at function's name and the
compiler's warning message for potential GC call.
As far as data goes this is about as good as we can get, the next phase
is labeling this stuff with potential solution(s). Again doing all by
hand is tedious and hardly useful.
Instead we need to observe patterns and label it automatically until the
non-trivial subset remains. So everybody, please take time and identify
simple patterns and post back your ideas on solution(s).
So far I see the most frequent cases:
- `new SomeException` - switch to RC exceptions
- AA access - ??? (use user-defined AA type as parameter?)
- array concat - ???
- closure - ???
I did some processing of the data and this is the results I got:
772 | 'new' causes GC allocation
515 | operator ~= may cause GC allocation
380 | operator ~ may cause GC allocation
113 | array literal may cause GC allocation
90 | setting 'length' may cause GC allocation
77 | indexing an associative array may cause GC allocation
34 | using closure causes GC allocation
16 | 'delete' requires GC
5 | associative array literal may cause GC allocation
Total 9
I didn't look at any source code to see what "new" is actually
allocating, for example.
--
/Jacob Carlborg
