I believe that old way won't work any more, correct. You might be able to hack it to, though - need to avoid capturing malloc and free in variables in the asm() function. If you use them from the global scope instead, that might be fine (but slower).
There is new work to trace malloc and free with the EMSCRIPTEN_TRACING flag (grep for it to see usages). But I'm not sure that is ready yet. You can also just manually implement malloc and free yourself. They are weakly linked, so you can override them easily. Or, you can just add some code in dlmalloc.c itself directly. - Alon On Tue, Jan 6, 2015 at 8:43 AM, Glenn Croes <[email protected]> wrote: > Hi, > > I'm trying to investigate an out-of-memory issue in a WebWorker that uses > a Emscripten compiled JS library. > For this, I would like to profile the memory usage / track memory > allocations. > I checked out the memory profiler from: > https://groups.google.com/forum/#!topic/emscripten-discuss/HtAzVposlX4. > It tries to hook into _malloc and _free by using a preRun callback. > However, this doesn't work anymore. Here is what it tries to do: > > *Webworker script* > importScripts("memoryprofiler-webworker.js"); > //...import Emscripten library through AMD loader... > > > *memoryprofiler-webworker.js* > //see > https://groups.google.com/forum/#!topic/emscripten-discuss/HtAzVposlX4 > function memoryprofiler_add_hooks(){ > var prevMalloc = _malloc; > //wrap prevMalloc in hookedMalloc > _malloc = hookedMalloc; > Module['_malloc'] = hookedMalloc; > //same with _free > } > > > *EmscriptenLibrary.js* > Module['preRun'] = [memoryprofiler_add_hooks]; > > The problem is that _malloc and _free are not in scope when entering the > memoryprofiler_add_hooks function. > > I've tried to pass the Module and asm objects to the > memoryprofiler_add_hooks function: > > *EmscriptenLibrary.js* > Module['preRun'] = []; > //... > //later on in the file, after asm object has been constructed (but before > the call to run()): > Module['preRun'].push({func: memoryprofiler_add_hooks, arg: {Module: > Module, asm: asm}}); > > *memoryprofiler-webworker.js* > function memoryprofiler_add_hooks(args) { > var prevMalloc = args.asm._malloc; > function hookedMalloc(size) { > //.. track memory statistics etc. and delegate to prevMalloc > } > args.asm['_malloc'] = hookedMalloc; > args.Module['_malloc'] = hookedMalloc; > //same with free > } > > This works as expected when you call asm._malloc or Module._malloc (or > EmscriptenLibrary._malloc from the webworker). It is hookedMalloc that gets > called instead of the asm _malloc. However, because compiled ASM code > refers to _malloc from inside of the asm object, the original asm._malloc > is still used by compiled ASM code. > > *EmscriptenLibrary.js* > // EMSCRIPTEN_START_ASM > var asm = (function(global, env, buffer) { > ... > function _malloc($bytes) { > ... > } > > function compiled_library_function(){ > ... > _malloc(...); //calls original _malloc, not hookedMalloc, no > statistics are tracked > ... > } > } > > > My question is: Is there any way to hook _malloc or _free? Can I do it > from an external JS with minimal modifications to Emscripten's output? Is > it possible by other means (e.g. linking a JS library)? An Emscripten > memory profiler would be great for developing Emscripten-based JS libraries. > > Kind regards, > Glenn > > > > > > -- > You received this message because you are subscribed to the Google Groups > "emscripten-discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
