From: "Eregon (Benoit Daloze)" Date: 2012-07-25T19:47:01+09:00 Subject: [ruby-core:46760] [ruby-trunk - Feature #6714] Code injection framework Issue #6714 has been updated by Eregon (Benoit Daloze). ko1 (Koichi Sasada) wrote: > Nobody has interest about it. I don't think so, I think it's just not clear what can offer this in practice yet. The use-cases you listed are certainly interesting. Would this, for example, significantly improve lib/debug.rb and lib/profiler.rb speed? (My question is more about the API being able to replace set_trace_func in these scenarios) > However set_trace_func() injects codes every tracing points. It cause huge performance impact if you have interest restricted places. Do you think this would be significantly faster for method tracing as in your example? It avoids other type of events (and does not generate binding and such), but it still is invoked at every method call. Maybe it would be worth to have an API which can give the method name, like `each_point(:invoke_method, :m1)`. I think it would be interesting to have the ability to reuse the original call(iseq?) in replace_proc, to wrap it inside other code, which can not easily be written with insert_before/after. ---------------------------------------- Feature #6714: Code injection framework https://bugs.ruby-lang.org/issues/6714#change-28432 Author: ko1 (Koichi Sasada) Status: Assigned Priority: Normal Assignee: ko1 (Koichi Sasada) Category: core Target version: 2.0.0 =begin = Abstract Introducing code injection framework. Different from set_trace_func(), this framework injects codes only specified points. Note that this proposal is not implemented and well designed (only rough idea) but I dumped it to discuss about this topic. It has (huge) possibility to miss 2.0 spec deadline (should be 3.0 spec?). = Background To trace, debug, profile and any analysis ruby code, Ruby provides `set_trace_func()' method. set_trace_func() is enough powerful to do them. However set_trace_func() injects codes every tracing points. It cause huge performance impact if you have interest restricted places. Another problem is that set_trace_func() can not affect program behavior. For example, we can not insert type checking code for specific method invocation. Related works with introducing codes are described below. Please point out if you know another related works. == Bytecode instrumentation JVM has JVMTI interface to inject any code with bytecode instrumentation. It can be done because JVM bytecode is well defined and become concrete specification. However, Ruby doesn't have any well-defined common bytecode and difficult to make such common bytecode (at least Ruby 2.0 spec deadline, this August). Manipulate bytecode directly has other problems: * Needs more knowledge about bytecode * Difficult to make `well-formed' bytecode sequence == AOP (Aspect Oriented Programming) Aspect-Oriented programming frameworks provides `join points' which we can insert codes . Such `join points' design is well abstracted comparing with bytecode instrumentation. In fact, AOT compilers such as Aspect-J use bytecode instrumentation. == Module#prepend We already have Module#prepend that enable to insert any program before/after method invocation. Example: module EachTracer # call tracing method before/after each method def each(*args) before_each begin super # call original each ensure after_each end end end class Array prepend EachTracer def before_each p:before_each end def after_each p:after_each end end %w(a b c).each{|c|} #=> outputs :before_each and :after_each However, Module#prepend only works for method invocation. = Proposal Introduce code injection framework. It should provide two features: (1) "where should insert codes?" and (2) "what code should be insert?". RubyVM::InstructionSequence#each_point(point_name) is temporal API for (1). each_point invoke block with CodePoint object. CodePint#set_proc (or something) is for (2). Example (it is rough API idea): def m1 m2(1) m2(1, 2, 3) m3() m4() end # insert proc before m2 method invocation method(:m1).iseq.each_point(:before_call){|point| # point is CodePoint object. if point.selector == :m2 point.set_proc{|*args| p "before call m2 with #{args.inspect}" } end } # another idea method(:m1).iseq.each_point(:invoke_method){|point| if point.selector == :m2 point.insert_proc_before{|*args| p "before call m2 with #{args.inspect}" } else point.selector == :m3 point.insert_proc_after{|retval| p "after call m2 with return value #{retval}" } else point.slector == :m4 point.replace_proc{|*args| p "cancel invoking m4 and call this proc instead" } end end Injection points are categorized into 3 types: * (1) before/after invoke something * method call (before method call) * method call (after method call) * block invocation (before) * block invocation (after) * super invocation (before) * super invocation (after) * (2) enter/leave (not needed?) * method (enter) (set_trace_func/call) * method (leave) (set_trace_func/return) * class/module definition (enter) (set_trace_func/class) * class/module definition (leave) (set_trace_func/end) * block (enter) * block (leave) * rescue (enter) * rescue (leave) * ensure (enter) * ensure (leave) * (3) misc * read variable ($gv, @iv, @@cv) * write variable ($gv, @iv, @@cv) * read constant (Const) * define constant (Const) * method definition * newline (set_trace_func/line) This proposal can introduce (limited) code manipulation without any bytecode knowledge. == Usecase * inserting specific break points for debugger * inserting specific analysis points for profiler * inserting type checking code generated by rdoc * making Aspect-J like tool (note that Module#prepend is enough if you only want to replace method invocation behavior) Any other idea? == Limitation It is impossible to inject any code into methods implemented by C. I'm afraid that this proposed API makes magical (unreadable) codes for script kiddies :P I repeat it again: Note that this proposal is not implemented and well designed (only rough idea) but I dumped it to discuss about this topic. It has (huge) possibility to miss 2.0 spec deadline (should be 3.0 spec?). Thanks, Koichi =end -- http://bugs.ruby-lang.org/