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Configuring ReDex

ReDex can be configured to run different optimizations or to alter the behavior of existing optimizations. While this isn't always necessary, it's helpful to be able to tweak settings to get the best results.

A Simple Example

A starting point for configuration is to use a configuration similar to the default config that's baked in to the redex binary. You can find this config in config/default.config. This is what it looks like:

{
"redex" : {
  "passes" : [
    "ReBindRefsPass",
    "BridgeSynthInlinePass",
    "FinalInlinePassV2",
    "DelSuperPass",
    "SingleImplPass",
    "MethodInlinePass",
    "StaticReloPassV2",
    "RemoveUnreachablePass",
    "ShortenSrcStringsPass",
    "RegAllocPass"
  ]
}
}

Name this file default.config, and invoke redex with it:

% redex.py -c default.config -o tmp/output.apk input.apk

This will do... exactly what redex does without the config. Not so exciting, is it? Let's move on to something more advanced.

Selecting Optimization Passes

Changing the set of optimizations ReDex runs is easy; just add (or remove) the pass name from the redex.passes list. For example, let's say you want to remove the ShortenSrcStrings optimization while you're debugging something. Just use this config:

{
"redex" : {
  "passes" : [
    "ReBindRefsPass",
    "BridgeSynthInlinePass",
    "FinalInlinePass",
    "DelSuperPass",
    "SingleImplPass",
    "MethodInlinePass",
    "RemoveUnreachablePass",
    "RegAllocPass"
  ]
}
}

Configuring optimization behavior

Each optimization pass has some configurable parameters that are specific to that pass. These are often blocklists (or allowlists) indicating what code the optimization should leave alone (for blocklists) or what code should be optimized (for allowlists).

A simple example is ShortenSrcStrings. This pass removes filenames indicating what source code produced each class. It's a waste to ship those source strings to production, but it's useful to be able to map the shortened names back to the original names (e.g., for solving user bug reports). You can tell ShortenSrcStrings to produce this map by adding a config entry:

"redex" : {
  "passes" : [
    ShortenSrcStringsPass,
    "RegAllocPass"
  ]
},
"ShortenSrcStringsPass" : {
  "filename_mappings" : "/tmp/filename_mappings.txt"
}

Options for each pass are documented with that pass.

Global options

  • redex.passes Type: array of strings A list of passes to be run in the specified order.

  • coldstart_classes Type: string Path to a file containing a list of class names in the order they are used for cold start. Example format:

    com/foo/Bar.class
    com/foo/Baz.class
    ...
    com/foo/Quux.class

  • proguard_map Type: string Path to a file containing ProGuard's mapping of unobfuscated class/field/method names to obfuscated names. This option is useful if you are running ReDex after ProGuard, so that ReDex will properly understand obfuscated names.

Complete configuration

To see the (almost) complete list of configuration parameters, run

redex-all --reflect-config

(Note that you run redex-all here, not the redex.py wrapper!)

This emits a JSON document detailing parameters, their types, defaults and possibly documentation.