# Compile

mruby is using Rake to compile and cross-compile all libraries and
binaries.

## Prerequisites

To compile mruby out of the source code you need the following tools:
* C Compiler (i.e. ```gcc```)
* Linker (i.e. ```gcc```)
* Archive utility (i.e. ```ar```)
* Parser generator (i.e. ```bison```)
* Ruby 1.8 or 1.9 (i.e. ```ruby``` or ```jruby```)

Optional:
* GIT (to update mruby source and integrate mrbgems easier)
* C++ compiler (to use GEMs which include *.cpp)
* Assembler (to use GEMs which include *.asm)

## Usage

Inside of the root directory of the mruby source a file exists
called *build_config.rb*. This file contains the build configuration
of mruby and looks like this for example:

	MRuby::Build.new do |conf|
	  toolchain :gcc
	end

All tools necessary to compile mruby can be set or modified here. In case
you want to maintain an additional *build_config.rb* you can define a
customized path using the *$MRUBY_CONFIG* environment variable.

To compile just call ```./minirake``` inside of the mruby source root. To
generate and execute the test tools call ```./minirake test```. To clean
all build files call ```./minirake clean```. To see full command line on 
build, call ```./minirake -v```.

## Build Configuration

Inside of the *build_config.rb* the following options can be configured
based on your environment.

### Toolchains

The mruby build system already contains a set of toolchain templates which
configure the build environment for specific compiler infrastructures.

#### GCC

Toolchain configuration for the GNU C Compiler.

	toolchain :gcc

#### clang

Toolchain configuration for the LLVM C Compiler clang. Mainly equal to the
GCC toolchain.

	toolchain :clang

#### Visual Studio 2010, 2012 and 2013

Toolchain configuration for Visual Studio on Windows. If you use the
[Visual Studio Command Prompt](http://msdn.microsoft.com/en-us/library/ms229859\(v=vs.110\).aspx),
you normally do not have to specify this manually, since it gets automatically detected by our build process.

	toolchain :visualcpp

#### Android

Toolchain configuration for Android.

	toolchain :androideabi

Requires the custom standalone Android NDK and the toolchain path
in ```ANDROID_STANDALONE_TOOLCHAIN```.

### Binaries

It is possible to select which tools should be compiled during the compilation
process. The following tools can be selected:
* mruby (mruby interpreter)
* mirb (mruby interactive shell)

To select them declare conf.gem as follows:

	conf.gem "#{root}/mrbgems/mruby-bin-mruby"

	conf.gem "#{root}/mrbgems/mruby-bin-mirb"

### File Separator

Some environments require a different file separator character. It is possible to
set the character via ```conf.file_separator```.

	conf.file_separator = '/'

### C Compiler

Configuration of the C compiler binary, flags and include paths.

	conf.cc do |cc|
	  cc.command = ...
	  cc.flags = ...
	  cc.include_paths = ...
	  cc.defines = ...
	  cc.option_include_path = ...
	  cc.option_define = ...
	  cc.compile_options = ...
	end

### Linker

Configuration of the Linker binary, flags and library paths.

	conf.linker do |linker|
	  linker.command = ...
	  linker.flags = ...
	  linker.flags_before_libraries = ...
	  linker.libraries = ...
	  linker.flags_after_libraries = ...
	  linker.library_paths = ....
	  linker.option_library = ...
	  linker.option_library_path = ...
	  linker.link_options = ...
	end

### Archiver

Configuration of the Archiver binary and flags.

	conf.archiver do |archiver|
	  archiver.command = ...
	  archiver.archive_options = ...
	end

### Parser Generator

Configuration of the Parser Generator binary and flags.

	conf.yacc do |yacc|
	  yacc.command = ...
	  yacc.compile_options = ...
	end

### GPerf

Configuration of the GPerf binary and flags.

	conf.gperf do |gperf|
	  gperf.command = ...
	  gperf.compile_options = ...
	end

### File Extensions

	conf.exts do |exts
	  exts.object = ...
	  exts.executable = ...
	  exts.library = ...
	end

### Mrbgems

Integrate GEMs in the build process.

	# Integrate GEM with additional configuration
	conf.gem 'path/to/gem' do |g|
	  g.cc.flags << ...
	end

	# Integrate GEM without additional configuration
	conf.gem 'path/to/another/gem'


See doc/mrbgems/README.md for more option about mrbgems.
### Mrbtest

Configuration Mrbtest build process.

If you want mrbtest.a only, You should set ```conf.build_mrbtest_lib_only```

	conf.build_mrbtest_lib_only


## Cross-Compilation

mruby can also be cross-compiled from one platform to another. To
achieve this the *build_config.rb* needs to contain an instance of
```MRuby::CrossBuild```. This instance defines the compilation
tools and flags for the target platform. An example could look
like this:

	MRuby::CrossBuild.new('32bit') do |conf|
	  toolchain :gcc

	  conf.cc.flags << "-m32"
	  conf.linker.flags << "-m32"
	end

All configuration options of ```MRuby::Build``` can also be used
in ```MRuby::CrossBuild```.

## Build process

During the build process the directory *build* will be created in the
root directory. The structure of this directory will look like this:

	+- build
	   |
	   +-  host
	       |
	       +- bin          <- Binaries (mirb, mrbc and mruby)
	       |
	       +- lib          <- Libraries (libmruby.a and libmruby_core.a)
	       |
	       +- mrblib
	       |
	       +- src
	       |
	       +- test         <- mrbtest tool
	       |
	       +- tools
	          |
	          +- mirb
	          |
	          +- mrbc
	          | 
	          +- mruby

The compilation workflow will look like this:
* compile all files under *src* (object files will be stored 
in *build/host/src*)
* generate parser grammar out of *src/parse.y* (generated
result will be stored in *build/host/src/y.tab.c*)
* compile  *build/host/src/y.tab.c* to  *build/host/src/y.tab.o*
* create *build/host/lib/libmruby_core.a* out of all object files (C only)
* create ```build/host/bin/mrbc``` by compiling *tools/mrbc/mrbc.c* and
linking with *build/host/lib/libmruby_core.a* 
* create *build/host/mrblib/mrblib.c* by compiling all *.rb files
under *mrblib* with ```build/host/bin/mrbc```
* compile *build/host/mrblib/mrblib.c* to *build/host/mrblib/mrblib.o* 
* create *build/host/lib/libmruby.a* out of all object files (C and Ruby)
* create ```build/host/bin/mruby``` by compiling *mrbgems/mruby-bin-mruby/tools/mruby/mruby.c* and
linking with *build/host/lib/libmruby.a*
* create ```build/host/bin/mirb``` by compiling *mrbgems/mruby-bin-mirb/tools/mirb/mirb.c* and
linking with *build/host/lib/libmruby.a*

```
 _____    _____    ______    ____    ____    _____    _____    ____
| CC  |->|GEN  |->|AR    |->|CC  |->|CC  |->|AR   |->|CC   |->|CC  |
| *.c |  |y.tab|  |core.a|  |mrbc|  |*.rb|  |lib.a|  |mruby|  |mirb|
 -----    -----    ------    ----    ----    -----    -----    ----
```

### Cross-Compilation

In case of a cross-compilation to *i386* the *build* directory structure looks
like this:

	+- build
	   |
	   +-  host
	   |   |
	   |   +- bin           <- Native Binaries
	   |   |
	   |   +- lib           <- Native Libraries
	   |   |
	   |   +- mrblib
	   |   |
	   |   +- src
	   |   |
	   |   +- test          <- Native mrbtest tool
	   |   |
	   |   +- tools
	   |      |
	   |      +- mirb
	   |      |
	   |      +- mrbc
	   |      | 
	   |      +- mruby 
	   +- i386
	      |
	      +- bin            <- Cross-compiled Binaries
	      |
	      +- lib            <- Cross-compiled Libraries
	      |
	      +- mrblib
	      |
	      +- src
	      |
	      +- test           <- Cross-compiled mrbtest tool
	      |
	      +- tools
	         |
	         +- mirb
	         |
	         +- mrbc
	         | 
	         +- mruby

An extra directory is created for the target platform. In case you
compile for *i386* a directory called *i386* is created under the
build direcotry.

The cross compilation workflow starts in the same way as the normal
compilation by compiling all *native* libraries and binaries.
Afterwards the cross compilation process proceeds like this:
* cross-compile all files under *src* (object files will be stored 
in *build/i386/src*)
* generate parser grammar out of *src/parse.y* (generated
result will be stored in *build/i386/src/y.tab.c*)
* cross-compile *build/i386/src/y.tab.c* to *build/i386/src/y.tab.o*
* create *build/i386/mrblib/mrblib.c* by compiling all *.rb files
under *mrblib* with the native ```build/host/bin/mrbc```
* cross-compile *build/host/mrblib/mrblib.c* to *build/host/mrblib/mrblib.o*
* create *build/i386/lib/libmruby.a* out of all object files (C and Ruby)
* create ```build/i386/bin/mruby``` by cross-compiling *mrbgems/mruby-bin-mruby/tools/mruby/mruby.c* and
linking with *build/i386/lib/libmruby.a*
* create ```build/i386/bin/mirb``` by cross-compiling *mrbgems/mruby-bin-mirb/tools/mirb/mirb.c* and
linking with *build/i386/lib/libmruby.a*
* create *build/i386/lib/libmruby_core.a* out of all object files (C only)
* create ```build/i386/bin/mrbc``` by cross-compiling *tools/mrbc/mrbc.c* and
linking with *build/i386/lib/libmruby_core.a* 

```
 _______________________________________________________________
|              Native Compilation for Host System               |
|  _____      ______      _____      ____      ____      _____  |
| | CC  | -> |AR    | -> |GEN  | -> |CC  | -> |CC  | -> |AR   | |
| | *.c |    |core.a|    |y.tab|    |mrbc|    |*.rb|    |lib.a| |
|  -----      ------      -----      ----      ----      -----  |
 ---------------------------------------------------------------
                                ||
                               \||/
                                \/
 ________________________________________________________________
|             Cross Compilation for Target System                |
|  _____      _____      _____      ____      ______      _____  |
| | CC  | -> |AR   | -> |CC   | -> |CC  | -> |AR    | -> |CC   | |
| | *.c |    |lib.a|    |mruby|    |mirb|    |core.a|    |mrbc | |
|  -----      -----      -----      ----      ------      -----  |
 ----------------------------------------------------------------
```

## Build Configuration Examples

### Minimal Library

To build a minimal mruby library you need to use the Cross Compiling 
feature due to the reason that there are functions (i.e. stdio) which 
can't be disabled for the main build.

	MRuby::CrossBuild.new('Minimal') do |conf|
	  toolchain :gcc

	  conf.cc.defines = %w(DISABLE_STDIO)
	  conf.bins = []  
	end

This configuration defines a cross compile build called 'Minimal' which
is using the GCC and compiles for the host machine. It also disables
all usages of stdio and doesn't compile any binaries (i.e. mrbc).

## Test Environment

mruby's build process includes a test environment. In case you start the testing
of mruby, a native binary called ```mrbtest``` will be generated and executed.
This binary contains all test cases which are defined under *test/t*. In case
of a cross-compilation an additional cross-compiled *mrbtest* binary is 
generated. You can copy this binary and run on your target system.
