This is my second post in a weekly series, where I attempt to distill my week down into some lessons or facts that I’ve picked up. Let’s get to it!<\/p>\n
As of March 27, 2015, ES6 classes<\/a> are still not yet safe for use in production browser code. There’s code to support them in Firefox, but they’re Nightly-only behind a build-time pref.<\/p>\n Array.prototype.includes<\/a> and ArrayBuffer.transfer<\/a> are also Nightly only at this time.<\/p>\n However, any of the rest of the ES6 Harmony work currently implemented by Nightly<\/a> is fair-game for use, according to jorendorff. The JS team is also working on a Wiki page to tell us Firefox developers what ES6 stuff is safe for use and what is not.<\/p>\n Update [January 23rd, 2017]: <\/strong>Markus Stange contacted me to let me know that the function mozilla_sampler_save_profile_to_file has been changed to profiler_save_profile_to_file. This happened in this bug<\/a>. I’ve updated the post to reflect this.<\/p>\n According to mstange, it is possible to get profiles from hung Firefox processes using lldb1<\/a><\/sup>.<\/p>\n To graft symbols into the profile. mstange’s scripts do some fairly clever things to get those symbols – if your Firefox was built by Mozilla, then it will retrieve the symbols from the Mozilla symbol server. If you built Firefox yourself, it will attempt to use some cleverness3<\/a><\/sup> to grab the symbols from your binary.<\/p>\n Your profile will now, hopefully, be updated with symbols.<\/p>\n Then, load up Cleopatra<\/a>, and upload the profile.<\/p>\n I haven’t yet had the opportunity to try this, but I hope to next week. I’d be eager to hear people’s experience giving this a go – it might be a great tool in determining what’s going on in Firefox when it’s hung4<\/a><\/sup>!<\/li>\n<\/ol>\n I noticed that when I talked about “things that I passed to functions5<\/a><\/sup>”, I would use “arguments” and “parameters” interchangeably. I recently learned that there is more to those terms than I had originally thought.<\/p>\n According to this MSDN article<\/a>, an argument is what is passed in to a function by a caller. To the function, it has received parameters. It’s like two sides of a coin. Or, as the article puts it, like cars and parking spaces:<\/p>\n You can think of the parameter as a parking space and the argument as an automobile. Just as different automobiles can park in a parking space at different times, the calling code can pass a different argument to the same parameter every time that it calls the procedure.6<\/a><\/sup><\/a><\/p><\/blockquote>\n Not that it really makes much difference, but I like knowing the details.<\/p>\n Unfortunately, this technique will not work for Windows. \ud83d\ude41 ↩<\/a><\/p><\/li> Assuming you’re running a build after this revision<\/a> landed. ↩<\/a><\/p><\/li> A binary called dump_syms_mac in mstange’s toolkit, and nm on Linux ↩<\/a><\/p><\/li> I’m particularly interested in knowing if we can get Javascript stacks via this technique – I can see that being particularly useful with hung content processes. ↩<\/a><\/p><\/li> Or methods. ↩<\/a><\/p><\/li> Source ↩<\/a><\/p><\/li><\/ol>","protected":false},"excerpt":{"rendered":" This is my second post in a weekly series, where I attempt to distill my week down into some lessons or facts that I’ve picked up. Let’s get to it! ES6 – what’s safe to use in browser development? As of March 27, 2015, ES6 classes are still not yet safe for use in production […]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"Things I've Learned This Week (March 30 - April 3, 2015) https:\/\/wp.me\/prmTy-Hx","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5,861,110],"tags":[1134,1129,1130,1128,1127,1018,1132,1121,1133,1135,1131],"class_list":["post-2699","post","type-post","status-publish","format-standard","hentry","category-computer-science","category-mozilla-2","category-musings","tag-arguments","tag-array-prototype-includes","tag-arraybuffer-transfer","tag-classes","tag-es6-harmony","tag-gecko","tag-hung","tag-lessons","tag-lldb","tag-parameters","tag-profile"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/prmTy-Hx","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/posts\/2699","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/comments?post=2699"}],"version-history":[{"count":7,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/posts\/2699\/revisions"}],"predecessor-version":[{"id":2835,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/posts\/2699\/revisions\/2835"}],"wp:attachment":[{"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/media?parent=2699"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/categories?post=2699"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mikeconley.ca\/blog\/wp-json\/wp\/v2\/tags?post=2699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Getting a profile from a hung process<\/h2>\n
\n
p (void)profiler_save_profile_to_file(\"somepath\/profile.txt\")<\/pre>\n<\/li>\n
python symbolicate_profile.py somepath\/profile.txt<\/pre>\n
Parameter vs. Argument<\/h2>\n