pathname: improvements, cleanups, and new methods

- atomic_write: close file before renaming to prevent error:
  'Device or resource busy'
- ensure_writable: preserve executable bit
- new elf? and dynamic? methods

6 files changed, 30 insertions, 4 deletions

diff --git a/Library/Homebrew/extend/os/linux/extend/pathname.rb b/Library/Homebrew/extend/os/linux/extend/pathname.rb
new file mode 100644
index 000000000..eb6ea409b
--- /dev/null
+++ b/Library/Homebrew/extend/os/linux/extend/pathname.rb
@@ -0,0 +1,19 @@
+class Pathname
+  # @private
+  def elf?
+    # See: https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
+    read(4) == "\x7fELF"
+  end
+
+  # @private
+  def dynamic_elf?
+    if which "readelf"
+      popen_read("readelf", "-l", to_path).include?(" DYNAMIC ")
+    elsif which "file"
+      !popen_read("file", "-L", "-b", to_path)[/dynamic|shared/].nil?
+    else
+      raise StandardError, "Neither `readelf` nor `file` is available "\
+        "to determine whether '#{self}' is dynamically or statically linked."
+    end
+  end
+end
diff --git a/Library/Homebrew/os/mac/pathname.rb b/Library/Homebrew/extend/os/mac/extend/pathname.rb
index 5fd59e1e7..5fd59e1e7 100644
--- a/Library/Homebrew/os/mac/pathname.rb
+++ b/Library/Homebrew/extend/os/mac/extend/pathname.rb
diff --git a/Library/Homebrew/extend/os/mac/hardware/cpu.rb b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
index b97c280cd..a216db6ae 100644
--- a/Library/Homebrew/extend/os/mac/hardware/cpu.rb
+++ b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
@@ -1,5 +1,3 @@
-require "os/mac/pathname"
-
 module Hardware
   class CPU
     class << self
diff --git a/Library/Homebrew/extend/os/pathname.rb b/Library/Homebrew/extend/os/pathname.rb
new file mode 100644
index 000000000..5e6edeb30
--- /dev/null
+++ b/Library/Homebrew/extend/os/pathname.rb
@@ -0,0 +1,5 @@
+if OS.mac?
+  require "extend/os/mac/extend/pathname"
+elsif OS.linux?
+  require "extend/os/linux/extend/pathname"
+end
diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index b4c7ca959..82cf10be0 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -189,6 +189,9 @@ class Pathname
       rescue Errno::EPERM # rubocop:disable Lint/HandleExceptions
       end
 
+      # Close the file before renaming to prevent the error: Device or resource busy
+      # Affects primarily NFS.
+      tf.close
       File.rename(tf.path, self)
     ensure
       tf.close!
@@ -376,7 +379,7 @@ class Pathname
     saved_perms = nil
     unless writable_real?
       saved_perms = stat.mode
-      chmod 0644
+      FileUtils.chmod "u+rw", to_path
     end
     yield
   ensure
@@ -469,6 +472,8 @@ class Pathname
   end
 end
 
+require "extend/os/pathname"
+
 # @private
 module ObserverPathnameExtension
   class << self
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index cb4141f48..a5e12c924 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -3,7 +3,6 @@ require "development_tools"
 require "os/mac/version"
 require "os/mac/xcode"
 require "os/mac/xquartz"
-require "os/mac/pathname"
 require "os/mac/sdk"
 require "os/mac/keg"