Correctly override proguard options

Question

I'm playing with ProGuard in my current project and decided to try optimized android config (with gradle):

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

I didn't find any clear documentation about optimizations performed by proguard and android versions which are compatible with them:

-optimizations !code/simplification/arithmetic,!code/simplification/cast,!field/*,!class/merging/* 

Are they up-to-date if app min sdk version is 11?

So i decided to override it to give it a try in proguard-rules.pro:

-optimizations **
-printconfiguration "result.pro"

But final configuration isn't as i expected. It contains all rules combined:

-optimizations !code/simplification/arithmetic,!code/simplification/cast,!field/*,!class/merging/*,**

So how can option be correctly overridden in ProGuard? Or may be this line equals to -optimizations ** ?

Answer 1

It took me a bit of trial and error but eventually found out. To override the default ProGuard optimizations to, for example, apply everything but code/simplification/arithmetic then:

1. Add a -optimizations line to your ProGuard file and use * to represent all. For example, the following line:

   -optimizations !code/simplification/arithmetic,*
   

   means "enable all optimizations except code/simplification/arithmetic". The list of available optimizations is available in the official website and you can use * to enable/disable classes of optimizations (e.g. !field/*).

2. You have to make sure that your ProGuard rules file is loaded before the default ProGuard file by swapping the order of proguard-rules.pro and getDefaultProguardFile('proguard-android.txt') in the Gradle file so that proguard-rules.pro appears first:

   buildTypes {
     release {
       minifyEnabled false
       proguardFiles 'proguard-rules.pro', getDefaultProguardFile('proguard-android.txt')
     }
   }
   

The output should look something like this now:

Optimizing...
  Number of finalized classes:                 68
  Number of unboxed enum classes:              1
  Number of vertically merged classes:         0
  Number of horizontally merged classes:       3
  Number of removed write-only fields:         0   (disabled)
  Number of privatized fields:                 58
  Number of inlined constant fields:           375
  Number of privatized methods:                13
  Number of staticized methods:                37
  Number of finalized methods:                 210
  Number of removed method parameters:         290
  Number of inlined constant parameters:       236
  Number of inlined constant return values:    239
  Number of inlined short method calls:        35
  Number of inlined unique method calls:       114
  Number of inlined tail recursion calls:      0
  Number of merged code blocks:                4
  Number of variable peephole optimizations:   723
  Number of arithmetic peephole optimizations: 10
  Number of cast peephole optimizations:       0
  Number of field peephole optimizations:      0
  Number of branch peephole optimizations:     42
  Number of string peephole optimizations:     35
  Number of simplified instructions:           369
  Number of removed instructions:              5019
  Number of removed local variables:           154
  Number of removed exception blocks:          0
  Number of optimized local variable frames:   201