module Crystal

Defined in:


Constant Summary

BUILD_COMMIT = "cbf651aff"
BUILD_DATE = "2019-08-01"
CACHE_DIR = "/root/.cache/crystal"
DESCRIPTION = "Crystal 0.30.0 [cbf651aff] (2019-08-01)\n\nLLVM: 4.0.0\nDefault target: x86_64-unknown-linux-gnu"
LIBRARY_PATH = "/usr/bin/../lib/crystal/lib"
LLVM_VERSION = "4.0.0"
PATH = "/crystal/src:lib"
VERSION = "0.30.0"

Class Method Summary

Class Method Detail

def self.main(&block) #

Defines the main routine run by normal Crystal programs:

  • Initializes the GC
  • Invokes the given block
  • Handles unhandled exceptions
  • Invokes at_exit handlers
  • Flushes STDOUT and STDERR

This method can be invoked if you need to define a custom main (as in C main) function, doing all the above steps.

For example:

fun main(argc : Int32, argv : UInt8**) : Int32
  Crystal.main do
    elapsed = Time.measure do
      Crystal.main_user_code(argc, argv)
    puts "Time to execute program: #{elapsed}"

Note that the above is really just an example, almost the same can be accomplished with at_exit. But in some cases redefinition of C's main is needed.

[View source]
def self.main(argc : Int32, argv : Pointer(Pointer(UInt8))) #

Main method run by all Crystal programs at startup.

This setups up the GC, invokes your program, rescuing any handled exception, and then runs at_exit handlers.

This method is automatically invoked for you, so you don't need to invoke it.

However, if you need to define a special main C function, you can redefine main and invoke Crystal.main from it:

fun main(argc : Int32, argv : UInt8**) : Int32
  # some setup before Crystal main
  Crystal.main(argc, argv)
  # some cleanup logic after Crystal main

The Crystal.main can also be passed as a callback:

fun main(argc : Int32, argv : UInt8**) : Int32
  LibFoo.init_foo_and_invoke_main(argc, argv, ->Crystal.main)

Note that before Crystal.main is invoked the GC is not setup yet, so nothing that allocates memory in Crystal (like new for classes) can be used.

[View source]
def self.main_user_code(argc : Int32, argv : Pointer(Pointer(UInt8))) #

Executes the main user code. This normally is executed after initializing the GC and before executing at_exit handlers.

You should never invoke this method unless you need to redefine C's main function. See Crystal.main for more details.

[View source]