FernFlowerLegacy

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Examples:

java -jar fernflower.jar -hes=0 -hdc=0 c:\Temp\binary\ -e=c:\Java\rt.jar c:\Temp\source\

java -jar fernflower.jar -dgs=1 c:\Temp\binary\library.jar c:\Temp\binary\Boot.class c:\Temp\source\

4. Command line options

With the exception of mpm and urc the value of 1 means the option is activated, 0 - deactivated. Default value, if any, is given between parentheses.

Typically, the following options will be changed by user, if any: hes, hdc, dgs, mpm, ren, urc The rest of options can be left as they are: they are aimed at professional reverse engineers.

rbr (1): hide bridge methods rsy (0): hide synthetic class members din (1): decompile inner classes dc4 (1): collapse 1.4 class references das (1): decompile assertions hes (1): hide empty super invocation hdc (1): hide empty default constructor dgs (0): decompile generic signatures ner (1): assume return not throwing exceptions den (1): decompile enumerations rgn (1): remove getClass() invocation, when it is part of a qualified new statement lit (0): output numeric literals "as-is" asc (0): encode non-ASCII characters in string and character literals as Unicode escapes bto (1): interpret int 1 as boolean true (workaround to a compiler bug) nns (1): allow for not set synthetic attribute (workaround to a compiler bug) uto (1): consider nameless types as java.lang.Object (workaround to a compiler architecture flaw) udv (1): reconstruct variable names from debug information, if present rer (1): remove empty exception ranges fdi (1): de-inline finally structures mpm (0): maximum allowed processing time per decompiled method, in seconds. 0 means no upper limit ren (0): rename ambiguous (resp. obfuscated) classes and class elements urc : full name of user-supplied class implementing IIdentifierRenamer. It is used to determine which class identifiers should be renamed and provides new identifier names. For more information see section 5 inn (1): check for IntelliJ IDEA-specific @NotNull annotation and remove inserted code if found lac (0): decompile lambda expressions to anonymous classes nls (0): define new line character to be used for output. 0 - '\r\n' (Windows), 1 - '\n' (Unix), default is OS-dependent ind : indentation string (default is " " (3 spaces))

The default logging level is INFO. This value can be overwritten by setting the option 'log' as follows: log (INFO): possible values TRACE, INFO, WARN, ERROR

5. Renaming identifiers

Some obfuscators give classes and their member elements short, meaningless and above all ambiguous names. Recompiling of such code leads to a great number of conflicts. Therefore it is advisable to let the decompiler rename elements in its turn, ensuring uniqueness of each identifier.

Option 'ren' (i.e. -ren=1) activates renaming functionality. Default renaming strategy goes as follows:

• rename an element if its name is a reserved word or is shorter than 3 characters
• new names are built according to a simple pattern: (class|method|field)_
  You can overwrite this rules by providing your own implementation of the 4 key methods invoked by the decompiler while renaming. Simply pass a class that implements org.jetbrains.java.decompiler.main.extern.IIdentifierRenamer in the option 'urc' (e.g. -urc=com.mypackage.MyRenamer) to Fernflower. The class must be available on the application classpath.

The meaning of each method should be clear from naming: toBeRenamed determine whether the element will be renamed, while the other three provide new names for classes, methods and fields respectively.