Redex - A bytecode optimizer for Android apps

by Shohei Kawano

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͔Θͷ@shaunkawano A bytecode optimizer for Android apps Redex

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͔Θͷ@shaunkawano A bytecode optimizer for Android apps Redex http://fbredex.com

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Redex • What is Redex? • Redex and ProGurad • How does Redex optimize .dex ﬁles • Sample output • Usage / Tips (for Mac) • Conclusion

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What is Redex?

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What is Redex? • Android bytecode (dex) optimizer • Read, analyze and optimize .dex ﬁles • Initial commit: 2016.03.25 / ˒: ~3100 • Originally developed by Facebook, Inc. http://fbredex.com

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What is Redex? • Android bytecode (dex) optimizer • Read, analyze and optimize .dex ﬁles • Initial commit: 2016.03.25 / ˒: ~3100 • Originally developed by Facebook, Inc. http://fbredex.com “An APK optimized by ReDex should be smaller and faster than its source.”

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Redex and ProGuard

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Redex and ProGuard https://github.com/facebook/redex#how-does-this-compare-to-proguard • ProGuard optimizes .class ﬁles bytecode • ProGuard has more capabilities  e.g. it can reduce unused method parameters • You may need to conﬁgure proguard- rules.pro ProGuard

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Redex and ProGuard https://github.com/facebook/redex#how-does-this-compare-to-proguard • Redex optimizes .dex ﬁles bytecode • Redex can inline source codes that ProGuard misses to inline • Redex cannot reduce unused method parameters • No rules required Redex

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How does Redex optimize .dex ﬁles?

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How does Redex optimize .dex ﬁles? https://code.facebook.com/posts/1480969635539475/optimizing-android-bytecode-with-redex • Miniﬁcation • Reducing and minimizing strings without changing functionality • Inlining methods • Dead code elimination • etc.

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Sample output

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Sample output

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Sample Output APK SIZE: 4.6MB → 4.3MB

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Usage / Tips (for Mac)

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http://fbredex.com $ brew install autoconf automake libtool python3 $ brew install boost double-conversion gflags glog libevent jsoncpp Install Command Line Tools Install Dependent tools using Homebrew For “/usr/local must be writable!” error $ xcode-select —install Usage / Tips (for Mac) Tips! Maybe You need to confer appropriate permission: https://github.com/Homebrew/legacy-homebrew/issues/49895

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$ git clone https://github.com/facebook/redex.git  $ cd redex http://fbredex.com Clone Redex repository Build ReDex(May take some time) $ autoreconf -ivf && ./configure && make  ReDex your APK $ redex path/to/your.apk -o path/to/output.apk  Usage / Tips (for Mac)

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$ ANDROID_SDK=path_to_android_sdk redex ./target.apk -o ./output.apk http://fbredex.com For “Couldn't ﬁnd zipalign. See README.md..” Error Usage / Tips (for Mac) Execute the command with Android SDK path specified: Tips! Testing $ ./test/setup.sh $ cd test $ make check /Applications/Xcode.app/Contents/Developer/usr/bin/make libgtest_main.la make[2]: *** No rule to make target `gtest-1.7.0/src/ gtest-all.cc', needed by `gtest-1.7.0/src/ libgtest_main_la-gtest-all.lo'. Stop. make[1]: *** [check-am] Error 2 make: *** [check-recursive] Error 1 " https://github.com/facebook/redex/issues/177

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Conclusion

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Conclusion • Trying to shrink APK size is quite important (Especially the apps for developing countries). • ProGuarding and Redexing your APK to reduce its size if possible. (Facebook does.) • Maybe integrating with CI in the future?

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ﬁn. ͔Θͷ@shaunkawano A bytecode optimizer for Android apps Redex