# 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 exist a file
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```.

## Build Configuration

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

### Toolchains

The mruby build system contains already a set of toolchain templates which
configurates 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 2012

Toolchain configuration for Visual Studio 2012 on Windows.

```
toolchain :vs2012
```

### Binaries

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

To select all define an array in ```conf.bins```:
```
conf.bins = %(mrbc mruby 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.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'
```

## Cross-Compilation

mruby can also be cross-compiled from one platform to another. To
achive 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 compile *tools/mrbc/mrbc.c* and
link 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 compile *tools/mruby/mruby.c* and
link with *build/host/lib/libmruby.a*
* create ```build/host/bin/mirb``` by compile *tools/mirb/mirb.c* and
link 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.
Aftwards 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-compile *tools/mruby/mruby.c* and
link with *build/i386/lib/libmruby.a*
* create ```build/i386/bin/mirb``` by cross-compile *tools/mirb/mirb.c* and
link 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-compile *tools/mrbc/mrbc.c* and
link 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 ||
| -----      -----      -----      ----      ------      ----- |
 --------------------------------------------------------------
```

## 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. This binary you can copy and run on your target system.