From: "Eregon (Benoit Daloze)" Date: 2022-01-04T10:59:53+00:00 Subject: [ruby-core:106960] [Ruby master Feature#16663] Add block or filtered forms of Kernel#caller to allow early bail-out Issue #16663 has been updated by Eregon (Benoit Daloze). I also think the approach of yielding an enumerable while smart looks really complicated to implement properly, and I could imagine it might cause issues in some VMs. Also if I understand correctly, that would mean `enum.each` would start the stack walking and so the line at which `enum.foo` is called would matter, and there would need to be some magical filtering to remove `caller_locations` and the block from the stacktrace and everything until `enum.each`, or otherwise those would show up as extra entries which would be highly inconvenient. And I think .lazy would likely not work as then it'd iterate the backtrace of the lazy Fiber and not the original one. +1 for `Thread.each_caller_location` or `Kernel.each_caller_location` yielding `Thread::Backtrace::Location` objects as @jermeyevans0 proposed. (I give up on `find_caller*`, while more optimize-able it likely won't matter too much in practice in comparison to the costs of stack walking, and I agree the `each_*` variant is more intuitive in Ruby) ---------------------------------------- Feature #16663: Add block or filtered forms of Kernel#caller to allow early bail-out https://bugs.ruby-lang.org/issues/16663#change-95783 * Author: headius (Charles Nutter) * Status: Open * Priority: Normal ---------------------------------------- There are many libraries that use `caller` or `caller_locations` to gather stack information for logging or instrumentation. These methods generate an array of informational stack frames based on the current call stack. Both methods accept parameters for `level` (skip some number of Ruby frames) and `length` (only return this many frames). However many use cases are unable to provide one or both of these. Instrumentation uses, for example, may need to skip an unknown number of frames at the top of the trace, such as to dig out of rspec plumbing or active_record internals and report the first line of user code. In such cases, the typical pattern is to simply request *all* frames and then filter out the one that is desired. This leads to a great deal of wasted work gathering those frames and constructing objects to carry them to the user. On optimizing runtimes like JRuby and TruffleRuby, it can have a tremendous impact on performance, since each frame has a much higher cost than on CRuby. I propose that we need a new form of `caller` that takes a block for processing each element. ```ruby def find_matching_frame(regex) caller do |frame| return frame if frame.file =~ regex end end ``` An alternative API would be to allow passing a query object as a keyword argument, avoiding the block dispatch by performing the match internally: ```ruby def find_matching_frame(regex) caller(file: regex) end ``` This API would provide a middle ground between explicitly specifying a maximum number of stack frames and asking for all frames. Most common, hot-path uses of `caller` could be replaced by these forms, reducing overhead on all Ruby implementations and drastically reducing it where stack traces are expensive. -- https://bugs.ruby-lang.org/ Unsubscribe: