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4.1.6 Checking for a Package Configuration		Table of ContentsNext »
4.2 Build Operations

4.1.7 Custom Configuration Checks

The Rsconscript author can add custom configuration checks to be performed during the rscons configure operation.

Here is an example from build_tests/configure/custom_config_check.rb showing a custom configuration check:

configure do
  custom_check("Checking 'grep' version") do |op|
    stdout, stderr, status = op.log_and_test_command(%w[grep --version])
    should_fail = true
    if status != 0
      fail_message = "error executing grep"
    elsif stdout =~ /^grep \(GNU grep\) 1\./
      fail_message = "too old!"
      status = 1
    elsif stdout =~ /^grep \(GNU grep\) 2\./
      fail_message = "we'll work with it but you should upgrade"
      status = 1
      should_fail = false
      op.store_merge("CPPDEFINES" => "GREP_WORKAROUND")
    else
      op.store_append("CPPDEFINES" => "GREP_FULL")
    end
    op.complete(status, success_message: "good!", fail_message: fail_message, fail: should_fail)
  end
  custom_check("Checking sed -E flag") do |op|
    stdout, stderr, status = op.log_and_test_command(%w[sed -E -e s/ab+/rep/], stdin: "abbbc")
    op.complete(stdout =~ /repc/ ? 0 : 1, success_message: "good", fail_message: "fail")
  end
end

build do
  Environment.new do |env|
    puts env["CPPDEFINES"]
  end
end

A custom configuration check is created by calling the custom_check method and passing a block. The contents of the block should perform the custom configuration checking logic. This logic can include executing a test command or other arbitrary operations. An argument op is passed to the block. This object is an instance of the ConfigureOp class class and provides several methods that can be used to aid with the custom configuration check. The log_and_test_command method can be used to execute a test command and retrieve its results. The command and its output are also logged to the config.log file. The store_merge, store_append, and store_parse methods can be used to store construction variables for Environments created during the build operation. Finally, the complete method can be used to complete the configuration check and indicate a success or failure.

While performing a custom configuration check, it can sometimes be useful to be able to construct an Environment to use the set of default construction variables as defined so far in the configuration block, for example to expand construction variables to build a test command. The normal Environment class cannot be used within the configure block, however the BasicEnvironment class can be used for such a purpose.

For example, to expand the current ${CCCMD} value:

configure do
  custom_check("Checking something to do with CCCMD") do
    command = BasicEnvironment.new.expand_varref("${CCCMD}")
    # ...
  end
end
« Prev
4.1.6 Checking for a Package Configuration		Table of ContentsNext »
4.2 Build Operations