Instead of looking at the ARG_MAX size let the exception occur and ca…

…tch it.

This circumvents guessing the usable size of ARG_MAX and will also work on systems where it's not possible to query 'getconf ARG_MAX'. I feel much better about this as it leaves the original flow intact and will only split the work into two if exactly Errno::E2BIG is raised. This should work across Unix/Win/MacOS.

lib/slather/project.rb

@@ -144,17 +144,18 @@ def pathnames_per_binary(binary_path)
  def create_coverage_files_for_binary(binary_path, pathnames_per_binary)
  coverage_files = []
 
- # Chunk pathnames_per_binary into segments that do not exceed the OS ARG_MAX size for calls to llvm-cov
- # The size is padded with 10% to account for added spaces etc. in the final argument
- if pathnames_per_binary.join.size * 1.1 < self.class.max_os_argument_size
+ begin
  coverage_files.concat(create_coverage_files(binary_path, pathnames_per_binary))
- elsif pathnames_per_binary.count >=2
- # If pathnames_per_binary is too big it's split in two halfs which are then processed independently
- left,right = pathnames_per_binary.each_slice( (pathnames_per_binary.size/2.0).round ).to_a
- coverage_files.concat(create_coverage_files_for_binary(binary_path, left))
- coverage_files.concat(create_coverage_files_for_binary(binary_path, right))
- else 
- raise StandardError, "Errno::E2BIG: Argument list too long. A path in your project is close to the E2BIG limit. https://github.com/SlatherOrg/slather/pull/414"
+ rescue Errno::E2BIG => e
+ # pathnames_per_binary is too big for the OS to handle so it's split in two halfs which are processed independently
+ if pathnames_per_binary.count > 1
+ left, right = pathnames_per_binary.each_slice( (pathnames_per_binary.size/2.0).round ).to_a
+ coverage_files.concat(create_coverage_files_for_binary(binary_path, left))
+ coverage_files.concat(create_coverage_files_for_binary(binary_path, right))
+ else
+ # pathnames_per_binary contains one element which is too big for the OS to handle. 
+ raise e, "#{e}. A path in your project is close to the E2BIG limit. https://github.com/SlatherOrg/slather/pull/414", e.backtrace
+ end
  end
 
  coverage_files
@@ -297,14 +298,6 @@ def self.yml
  @yml ||= File.exist?(yml_filename) ? YAML.load_file(yml_filename) : {}
  end
 
- def self.get_arg_max
- @get_arg_max ||= `getconf ARG_MAX`.to_i
- end
-
- def self.max_os_argument_size
- self.get_arg_max > 0 ? self.get_arg_max : 26214
- end
-
  def configure
  begin
  configure_scheme

spec/slather/project_spec.rb

@@ -35,30 +35,6 @@
  end
  end
 
- describe "::max_os_argument_size" do
- let(:getconf_project) do
- Slather::Project.open(FIXTURES_PROJECT_PATH)
- end
-
- before(:each) do
- getconf_project.instance_variable_set("@get_arg_max", nil) 
- end
-
- context "getconf ARG_MAX returns a value" do
- it "should return a value" do
- allow(getconf_project.class).to receive(:get_arg_max).and_return(2000)
- expect(getconf_project.class.max_os_argument_size).to eq(2000)
- end
- end 
-
- context "getconf ARG_MAX does not return a value" do
- it "should return a value with a sensible default" do
- allow(getconf_project.class).to receive(:get_arg_max).and_return(0)
- expect(getconf_project.class.max_os_argument_size).to eq(26214)
- end
- end 
- end
-
  describe "#coverage_files" do
  class SpecCoverageFile < Slather::CoverageFile
  end
@@ -134,22 +110,24 @@ class SpecXcode7CoverageFile < Slather::ProfdataCoverageFile
  allow(Dir).to receive(:[]).with("#{fixtures_project.build_directory}/**/Coverage.profdata").and_return(["/some/path/Coverage.profdata"])
  allow(fixtures_project).to receive(:binary_file).and_return(["Fixtures"])
  allow(fixtures_project).to receive(:llvm_cov_export_output).and_return(llvm_cov_export_output)
- allow(fixtures_project).to receive(:profdata_llvm_cov_output).and_return(profdata_llvm_cov_output)
  allow(fixtures_project).to receive(:coverage_file_class).and_return(SpecXcode7CoverageFile)
  allow(fixtures_project).to receive(:ignore_list).and_return([])
  end
 
- it "Should raise an error when the OS level argument size is too small to work with" do
- allow(fixtures_project.class).to receive(:max_os_argument_size).and_return(10)
- expect { fixtures_project.send(:profdata_coverage_files) }.to raise_error(StandardError, "Errno::E2BIG: Argument list too long. A path in your project is close to the E2BIG limit. https://github.com/SlatherOrg/slather/pull/414")
+ it "Should catch Errno::E2BIG and re-raise if the input is too large to split into multiple chunks" do
+ allow(fixtures_project).to receive(:unsafe_profdata_llvm_cov_output).and_raise(Errno::E2BIG)
+ expect { fixtures_project.send(:profdata_coverage_files) }.to raise_error(Errno::E2BIG, "Argument list too long. A path in your project is close to the E2BIG limit. https://github.com/SlatherOrg/slather/pull/414")
  end
 
- it "Should return Coverage.profdata file objects when the OS level argument size is smaller than the input size" do
- allow(fixtures_project.class).to receive(:max_os_argument_size).and_return(llvm_cov_export_output.size/2)
- allow(fixtures_project).to receive(:profdata_llvm_cov_output).and_return(profdata_llvm_cov_output << profdata_llvm_cov_output)
+ it "Should catch Errno::E2BIG and return Coverage.profdata file objects when the work can be split into two" do
+ allow(fixtures_project).to receive(:unsafe_profdata_llvm_cov_output).once { 
+ # raise once and then insert the stub
+ allow(fixtures_project).to receive(:profdata_llvm_cov_output).and_return(profdata_llvm_cov_output)
+ raise Errno::E2BIG 
+ }
  profdata_coverage_files = fixtures_project.send(:profdata_coverage_files)
  profdata_coverage_files.each { |cf| expect(cf.kind_of?(SpecXcode7CoverageFile)).to be_truthy }
- expect(profdata_coverage_files.map { |cf| cf.source_file_pathname.basename.to_s }).to eq(["Fixtures.swift"])
+ expect(profdata_coverage_files.map { |cf| cf.source_file_pathname.basename.to_s }).to eq(["Fixtures.swift", "Fixtures.swift"])
  end
  end