scalac – Compiler for the Scala 2 language


scalac [ <options> ] <source files>


Command line options. See OPTIONS below.
<source files>
One or more source files to be compiled (such as MyClass.scala).


The scalac tool reads class and object definitions, written in the Scala programming language, and compiles them into bytecode class files.

By default, the compiler puts each class file in the same directory as its source file. You can specify a separate destination directory with -d (see OPTIONS, below).


The compiler has a set of standard options that are supported on the current development environment and will be supported in future releases. An additional set of non-standard options are specific to the current virtual machine implementation and are subject to change in the future. Non-standard options begin with -X.

Standard Options

Pass –Dproperty=value directly to the runtime system.
Pass <flag> directly to the runtime system.
Pass an option to a plugin
Print a synopsis of advanced options.
–bootclasspath <path>
Override location of bootstrap class files (where to find the standard built-in classes, such as "scala.List").
–classpath <path>
Specify where to find user class files (on Unix-based systems a colon-separated list of paths, on Windows-based systems, a semicolon-separated list of paths). This does not override the built-in ("boot") search path.
The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option overrides that default, so if you want to include the current directory in the search path, you must include "." in the new settings.
–d <directory|jar>
Specify where to place generated class files.
Emit warning and location for usages of deprecated APIs.
Available since Scala version 2.2.1
–encoding <encoding>
Specify character encoding used by source files.
The default value is platform-specific (Linux: "UTF8", Windows: "Cp1252"). Executing the following code in the Scala REPL will return the default value on your system:
scala> new
Explain type errors in more detail.
–extdirs <dirs>
Override location of installed extensions.
Emit warning and location for usages of features that should be imported explicitly.
"none" generates no debugging info,
"source" generates only the source file attribute,
"line" generates source and line number information,
"vars" generates source, line number and local variable information,
"notailcalls" generates all of the above and will not perform tail call optimization.
Print a synopsis of standard options.
–javabootclasspath <path>
Override Java boot classpath.
–javaextdirs <path>
Override Java extdirs classpath.
Enable one or more language features.
Ignore @specialize annotations.
Do not use the boot classpath for the Scala jar files.
Generate no warnings
Generates faster bytecode by applying optimisations to the program.
Print program with all Scala-specific features removed.
–sourcepath <path>
Specify location(s) of source files.
"jvm-1.8" target JVM 1.8 (default)
–toolcp <path>
Add to the runner classpath.
Enable detailed unchecked (erasure) warnings
Non variable type-arguments in type patterns are unchecked since they are eliminated by erasure
Available since Scala version 2.3.0
Uniquely tag all identifiers in debugging output.
Utilize the java.class.path in classpath resolution.
Utilize the manifest in classpath resolution.
Output messages about what the compiler is doing
Print product version and exit.
A text file containing compiler arguments (options and source files)

Advanced Options

Wrap field accessors to throw an exception on uninitialized access.
Enable warnings for developers working on the Scala compiler
Generate no assertions and assumptions
–Xelide-below <n>
Calls to @elidable methods are omitted if method priority is lower than argument.
Fail the compilation if there are any warnings.
Retain pre 2.10 behavior of less aggressive truncation of least upper bounds.
–Xgenerate-phase-graph <file>
Generate the phase graphs (outputs .dot files) to
Enable recommended additional warnings.
Print a message when reification creates a free term.
Print a message when reification resorts to generating a free type.
Print a message whenever an implicit conversion is inserted.
Print a message when a reflective method call is generated.
Custom settings for macros.
–Xmain-class <path>
Class for manifest's Main-Class entry (only useful with -d <jar>).
Warn about constructs whose behavior may have changed since<version>.
Do not generate static forwarders in mirror classes.
Don't perform exhaustivity/unreachability analysis. Also, ignore @switch annotation.
The JLine keybindings to use: emacs/vi/off.
Load a plugin from each classpath.
Disable plugins by name.
Print a synopsis of loaded plugins.
Abort if a named plugin is not loaded.
–Xpluginsdir <path>
Path to search for plugin archives.
Print out program after <phases> (see below).
Print tree positions, as offsets.
Print tree types (debugging option).
Display a prompt after each error (debugging option).
Compiler stays resident, files to compile are read from standard input.
–Xscript <object>
Treat the source file as a script and wrap it in a main method.
–Xshow-class <class>
Show internal representation of class.
–Xshow-object <object>
Show internal representation of object.
Print a synopsis of compiler phases.
Treat compiler input as Scala source for the specified version, see scala/bug#8126.
–Xsource-reader <classname>
Specify a custom method for reading source files.
Don't infer known-unsound types.
Verify generic signatures in generated bytecode (asm backend only).
Configure XML parsing.
"coalescing" convert PCData to Text and coalesce sibling nodes (default in 2.11).
Print a synopsis of private options.

Compilation Phases

parse source into ASTs, perform simple desugaring
resolve names, attach symbols to named trees
load package objects
the meat and potatoes: type the trees
translate match expressions
add super accessors in traits and nested classes
add extension methods for inline classes
serialize symbol tables
reference/override checking, translate nested objects
ANF pre-transform for @cps (CPS plugin)
@cps-driven transform of selectiveanf assignments (CPS plugin)
uncurry, translate function values to anonymous classes
replace tail calls by jumps
@specialized-driven class and method specialization
this refs to outer pointers, translate patterns
erase types, add interfaces for traits
clean up erased inline classes
synthesize accessors and fields, including bitmaps for lazy vals
move nested functions to top level
move field definitions into constructors
eliminate inner classes
mixin composition
platform-specific cleanups, generate reflective calls
remove lambdas
optimization: do inlining
optimization: inline exception handlers
optimization: eliminate uncalled closures
optimization: optimize null and other constants
optimization: eliminate dead code
generate JVM bytecode
the last phase in the compiler chain
matches all phases


Specify the java command to be used for running the Scala code. Arguments may be specified as part of the environment variable; spaces, quotation marks, etc., will be passed directly to the shell for expansion.
Specify JDK/JRE home directory. This directory is used to locate the java command unless JAVACMD variable set.
Specify the options to be passed to the java command defined by JAVACMD.
One might for example configure the memory usage of the JVM with: JAVA_OPTS="-Xmx2G -Xss16M"


Compile a Scala program to the current directory
scalac HelloWorld
Compile a Scala program to the destination directory classes
scalac –d classes HelloWorld.scala
Compile a Scala program using a user-defined java command
env JAVACMD=/usr/local/bin/cacao scalac –d classes HelloWorld.scala
Compile all Scala files found in the source directory src to the destination directory classes
scalac –d classes src/*.scala


scalac returns a zero exit status if it succeeds to compile the specified input files. Non zero is returned in case of failure.


Written by Martin Odersky and other members of the Scala team.


Report bugs to

This is open-source software, available to you under the Apache License 2.0. See accompanying "copyright" or "LICENSE" file for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


fsc(1), scala(1), scaladoc(1), scalap(1)

version 1.0
March 2012