Use JRuby implementation for TruffleRuby (#149)

Fix GH-145

Rename `lib/fiddle/jruby.rb` to `lib/fiddle/ffi_backend.rb` as a generic
ffi gem API based implementation.
JRuby and TruffleRuby use `lib/fiddle/ffi_backend.rb`.

---------

Co-authored-by: Benoit Daloze <[email protected]>

13 files changed, 156 insertions, 109 deletions

diff --git a/ext/fiddle/extconf.rb b/ext/fiddle/extconf.rb
index f062d1fc76..2899980657 100644
--- a/ext/fiddle/extconf.rb
+++ b/ext/fiddle/extconf.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 require 'mkmf'
 
-if RUBY_ENGINE == "jruby"
+unless RUBY_ENGINE == "ruby"
   File.write('Makefile', dummy_makefile("").join)
   return
 end
diff --git a/ext/fiddle/fiddle.gemspec b/ext/fiddle/fiddle.gemspec
index 65de7a30af..0092f52003 100644
--- a/ext/fiddle/fiddle.gemspec
+++ b/ext/fiddle/fiddle.gemspec
@@ -38,11 +38,10 @@ Gem::Specification.new do |spec|
     "lib/fiddle.rb",
     "lib/fiddle/closure.rb",
     "lib/fiddle/cparser.rb",
+    "lib/fiddle/ffi_backend.rb",
     "lib/fiddle/function.rb",
     "lib/fiddle/import.rb",
-    "lib/fiddle/jruby.rb",
     "lib/fiddle/pack.rb",
-    "lib/fiddle/ruby.rb",
     "lib/fiddle/struct.rb",
     "lib/fiddle/types.rb",
     "lib/fiddle/value.rb",
diff --git a/ext/fiddle/lib/fiddle.rb b/ext/fiddle/lib/fiddle.rb
index b1c6cd08bf..6718b012ef 100644
--- a/ext/fiddle/lib/fiddle.rb
+++ b/ext/fiddle/lib/fiddle.rb
@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
-require "fiddle/#{RUBY_ENGINE}"
+if RUBY_ENGINE == 'ruby'
+  require 'fiddle.so'
+else
+  require 'fiddle/ffi_backend'
+end
 require 'fiddle/closure'
 require 'fiddle/function'
 require 'fiddle/version'
diff --git a/ext/fiddle/lib/fiddle/jruby.rb b/ext/fiddle/lib/fiddle/ffi_backend.rb
index 9ad61d4d9d..0c7c379777 100644
--- a/ext/fiddle/lib/fiddle/jruby.rb
+++ b/ext/fiddle/lib/fiddle/ffi_backend.rb
@@ -1,4 +1,4 @@
-# This is part of JRuby's FFI-based fiddle implementation.
+# This is based on JRuby's FFI-based fiddle implementation.
 
 require 'ffi'
 
@@ -74,7 +74,7 @@ module Fiddle
 
   WINDOWS = FFI::Platform.windows?
 
-  module JRuby
+  module FFIBackend
     FFITypes = {
         'c' => FFI::Type::INT8,
         'h' => FFI::Type::INT16,
@@ -104,16 +104,16 @@ module Fiddle
         Types::VARIADIC => FFI::Type::Builtin::VARARGS,
     }
 
-    def self.__ffi_type__(dl_type)
-      if dl_type.is_a?(Symbol)
-        dl_type = Types.const_get(dl_type.to_s.upcase)
+    def self.to_ffi_type(fiddle_type)
+      if fiddle_type.is_a?(Symbol)
+        fiddle_type = Types.const_get(fiddle_type.to_s.upcase)
       end
-      if !dl_type.is_a?(Integer) && dl_type.respond_to?(:to_int)
-        dl_type = dl_type.to_int
+      if !fiddle_type.is_a?(Integer) && fiddle_type.respond_to?(:to_int)
+        fiddle_type = fiddle_type.to_int
       end
-      ffi_type = FFITypes[dl_type]
-      ffi_type = FFITypes[-dl_type] if ffi_type.nil? && dl_type.is_a?(Integer) && dl_type < 0
-      raise TypeError.new("cannot convert #{dl_type} to ffi") unless ffi_type
+      ffi_type = FFITypes[fiddle_type]
+      ffi_type = FFITypes[-fiddle_type] if ffi_type.nil? && fiddle_type.is_a?(Integer) && fiddle_type < 0
+      raise TypeError.new("cannot convert #{fiddle_type} to ffi") unless ffi_type
       ffi_type
     end
   end
@@ -133,8 +133,8 @@ module Fiddle
       @ptr, @args, @return_type, @abi = ptr, args, return_type, abi
       raise TypeError.new "invalid argument types" unless args.is_a?(Array)
 
-      ffi_return_type = Fiddle::JRuby::__ffi_type__(@return_type)
-      ffi_args = @args.map { |t| Fiddle::JRuby.__ffi_type__(t) }
+      ffi_return_type = Fiddle::FFIBackend.to_ffi_type(@return_type)
+      ffi_args = @args.map { |t| Fiddle::FFIBackend.to_ffi_type(t) }
       pointer = FFI::Pointer.new(ptr.to_i)
       options = {convention: @abi}
       if ffi_args.last == FFI::Type::Builtin::VARARGS
@@ -149,14 +149,25 @@ module Fiddle
       end
     end
 
-    def call(*args, &block);
+    def call(*args, &block)
       if @function.is_a?(FFI::VariadicInvoker)
         n_fixed_args = @args.size - 1
         n_fixed_args.step(args.size - 1, 2) do |i|
           if args[i] == :const_string || args[i] == Types::CONST_STRING
             args[i + 1] = String.try_convert(args[i + 1]) || args[i + 1]
           end
-          args[i] = Fiddle::JRuby.__ffi_type__(args[i])
+          args[i] = Fiddle::FFIBackend.to_ffi_type(args[i])
+        end
+      else
+        args.map! do |arg|
+          if arg.respond_to?(:to_ptr)
+            begin
+              arg = arg.to_ptr
+            end until arg.is_a?(FFI::Pointer) || !arg.respond_to?(:to_ptr)
+            arg
+          else
+            arg
+          end
         end
       end
       result = @function.call(*args, &block)
@@ -170,19 +181,21 @@ module Fiddle
       raise TypeError.new "invalid argument types" unless args.is_a?(Array)
 
       @ctype, @args = ret, args
-      ffi_args = @args.map { |t| Fiddle::JRuby.__ffi_type__(t) }
+      ffi_args = @args.map { |t| Fiddle::FFIBackend.to_ffi_type(t) }
       if ffi_args.size == 1 && ffi_args[0] == FFI::Type::Builtin::VOID
         ffi_args = []
       end
-      @function = FFI::Function.new(
-        Fiddle::JRuby.__ffi_type__(@ctype),
-        ffi_args,
-        self,
-        :convention => abi
-      )
+      return_type = Fiddle::FFIBackend.to_ffi_type(@ctype)
+      raise "#{self.class} must implement #call" unless respond_to?(:call)
+      callable = method(:call)
+      @function = FFI::Function.new(return_type, ffi_args, callable, convention: abi)
       @freed = false
     end
 
+    def to_ptr
+      @function
+    end
+
     def to_i
       @function.to_i
     end
@@ -550,51 +563,51 @@ module Fiddle
   RUBY_FREE = Fiddle::Pointer::LibC::FREE.address
   NULL = Fiddle::Pointer.new(0)
 
-  ALIGN_VOIDP       = Fiddle::JRuby::FFITypes[Types::VOIDP].alignment
-  ALIGN_CHAR        = Fiddle::JRuby::FFITypes[Types::CHAR].alignment
-  ALIGN_SHORT       = Fiddle::JRuby::FFITypes[Types::SHORT].alignment
-  ALIGN_INT         = Fiddle::JRuby::FFITypes[Types::INT].alignment
-  ALIGN_LONG        = Fiddle::JRuby::FFITypes[Types::LONG].alignment
-  ALIGN_LONG_LONG   = Fiddle::JRuby::FFITypes[Types::LONG_LONG].alignment
-  ALIGN_INT8_T      = Fiddle::JRuby::FFITypes[Types::INT8_T].alignment
-  ALIGN_INT16_T     = Fiddle::JRuby::FFITypes[Types::INT16_T].alignment
-  ALIGN_INT32_T     = Fiddle::JRuby::FFITypes[Types::INT32_T].alignment
-  ALIGN_INT64_T     = Fiddle::JRuby::FFITypes[Types::INT64_T].alignment
-  ALIGN_FLOAT       = Fiddle::JRuby::FFITypes[Types::FLOAT].alignment
-  ALIGN_DOUBLE      = Fiddle::JRuby::FFITypes[Types::DOUBLE].alignment
-  ALIGN_BOOL        = Fiddle::JRuby::FFITypes[Types::BOOL].alignment
-  ALIGN_SIZE_T      = Fiddle::JRuby::FFITypes[Types::SIZE_T].alignment
+  ALIGN_VOIDP       = Fiddle::FFIBackend::FFITypes[Types::VOIDP].alignment
+  ALIGN_CHAR        = Fiddle::FFIBackend::FFITypes[Types::CHAR].alignment
+  ALIGN_SHORT       = Fiddle::FFIBackend::FFITypes[Types::SHORT].alignment
+  ALIGN_INT         = Fiddle::FFIBackend::FFITypes[Types::INT].alignment
+  ALIGN_LONG        = Fiddle::FFIBackend::FFITypes[Types::LONG].alignment
+  ALIGN_LONG_LONG   = Fiddle::FFIBackend::FFITypes[Types::LONG_LONG].alignment
+  ALIGN_INT8_T      = Fiddle::FFIBackend::FFITypes[Types::INT8_T].alignment
+  ALIGN_INT16_T     = Fiddle::FFIBackend::FFITypes[Types::INT16_T].alignment
+  ALIGN_INT32_T     = Fiddle::FFIBackend::FFITypes[Types::INT32_T].alignment
+  ALIGN_INT64_T     = Fiddle::FFIBackend::FFITypes[Types::INT64_T].alignment
+  ALIGN_FLOAT       = Fiddle::FFIBackend::FFITypes[Types::FLOAT].alignment
+  ALIGN_DOUBLE      = Fiddle::FFIBackend::FFITypes[Types::DOUBLE].alignment
+  ALIGN_BOOL        = Fiddle::FFIBackend::FFITypes[Types::BOOL].alignment
+  ALIGN_SIZE_T      = Fiddle::FFIBackend::FFITypes[Types::SIZE_T].alignment
   ALIGN_SSIZE_T     = ALIGN_SIZE_T
-  ALIGN_PTRDIFF_T   = Fiddle::JRuby::FFITypes[Types::PTRDIFF_T].alignment
-  ALIGN_INTPTR_T    = Fiddle::JRuby::FFITypes[Types::INTPTR_T].alignment
-  ALIGN_UINTPTR_T   = Fiddle::JRuby::FFITypes[Types::UINTPTR_T].alignment
-
-  SIZEOF_VOIDP       = Fiddle::JRuby::FFITypes[Types::VOIDP].size
-  SIZEOF_CHAR        = Fiddle::JRuby::FFITypes[Types::CHAR].size
-  SIZEOF_UCHAR       = Fiddle::JRuby::FFITypes[Types::UCHAR].size
-  SIZEOF_SHORT       = Fiddle::JRuby::FFITypes[Types::SHORT].size
-  SIZEOF_USHORT      = Fiddle::JRuby::FFITypes[Types::USHORT].size
-  SIZEOF_INT         = Fiddle::JRuby::FFITypes[Types::INT].size
-  SIZEOF_UINT        = Fiddle::JRuby::FFITypes[Types::UINT].size
-  SIZEOF_LONG        = Fiddle::JRuby::FFITypes[Types::LONG].size
-  SIZEOF_ULONG       = Fiddle::JRuby::FFITypes[Types::ULONG].size
-  SIZEOF_LONG_LONG   = Fiddle::JRuby::FFITypes[Types::LONG_LONG].size
-  SIZEOF_ULONG_LONG  = Fiddle::JRuby::FFITypes[Types::ULONG_LONG].size
-  SIZEOF_INT8_T      = Fiddle::JRuby::FFITypes[Types::INT8_T].size
-  SIZEOF_UINT8_T     = Fiddle::JRuby::FFITypes[Types::UINT8_T].size
-  SIZEOF_INT16_T     = Fiddle::JRuby::FFITypes[Types::INT16_T].size
-  SIZEOF_UINT16_T    = Fiddle::JRuby::FFITypes[Types::UINT16_T].size
-  SIZEOF_INT32_T     = Fiddle::JRuby::FFITypes[Types::INT32_T].size
-  SIZEOF_UINT32_T    = Fiddle::JRuby::FFITypes[Types::UINT32_T].size
-  SIZEOF_INT64_T     = Fiddle::JRuby::FFITypes[Types::INT64_T].size
-  SIZEOF_UINT64_T    = Fiddle::JRuby::FFITypes[Types::UINT64_T].size
-  SIZEOF_FLOAT       = Fiddle::JRuby::FFITypes[Types::FLOAT].size
-  SIZEOF_DOUBLE      = Fiddle::JRuby::FFITypes[Types::DOUBLE].size
-  SIZEOF_BOOL        = Fiddle::JRuby::FFITypes[Types::BOOL].size
-  SIZEOF_SIZE_T      = Fiddle::JRuby::FFITypes[Types::SIZE_T].size
+  ALIGN_PTRDIFF_T   = Fiddle::FFIBackend::FFITypes[Types::PTRDIFF_T].alignment
+  ALIGN_INTPTR_T    = Fiddle::FFIBackend::FFITypes[Types::INTPTR_T].alignment
+  ALIGN_UINTPTR_T   = Fiddle::FFIBackend::FFITypes[Types::UINTPTR_T].alignment
+
+  SIZEOF_VOIDP       = Fiddle::FFIBackend::FFITypes[Types::VOIDP].size
+  SIZEOF_CHAR        = Fiddle::FFIBackend::FFITypes[Types::CHAR].size
+  SIZEOF_UCHAR       = Fiddle::FFIBackend::FFITypes[Types::UCHAR].size
+  SIZEOF_SHORT       = Fiddle::FFIBackend::FFITypes[Types::SHORT].size
+  SIZEOF_USHORT      = Fiddle::FFIBackend::FFITypes[Types::USHORT].size
+  SIZEOF_INT         = Fiddle::FFIBackend::FFITypes[Types::INT].size
+  SIZEOF_UINT        = Fiddle::FFIBackend::FFITypes[Types::UINT].size
+  SIZEOF_LONG        = Fiddle::FFIBackend::FFITypes[Types::LONG].size
+  SIZEOF_ULONG       = Fiddle::FFIBackend::FFITypes[Types::ULONG].size
+  SIZEOF_LONG_LONG   = Fiddle::FFIBackend::FFITypes[Types::LONG_LONG].size
+  SIZEOF_ULONG_LONG  = Fiddle::FFIBackend::FFITypes[Types::ULONG_LONG].size
+  SIZEOF_INT8_T      = Fiddle::FFIBackend::FFITypes[Types::INT8_T].size
+  SIZEOF_UINT8_T     = Fiddle::FFIBackend::FFITypes[Types::UINT8_T].size
+  SIZEOF_INT16_T     = Fiddle::FFIBackend::FFITypes[Types::INT16_T].size
+  SIZEOF_UINT16_T    = Fiddle::FFIBackend::FFITypes[Types::UINT16_T].size
+  SIZEOF_INT32_T     = Fiddle::FFIBackend::FFITypes[Types::INT32_T].size
+  SIZEOF_UINT32_T    = Fiddle::FFIBackend::FFITypes[Types::UINT32_T].size
+  SIZEOF_INT64_T     = Fiddle::FFIBackend::FFITypes[Types::INT64_T].size
+  SIZEOF_UINT64_T    = Fiddle::FFIBackend::FFITypes[Types::UINT64_T].size
+  SIZEOF_FLOAT       = Fiddle::FFIBackend::FFITypes[Types::FLOAT].size
+  SIZEOF_DOUBLE      = Fiddle::FFIBackend::FFITypes[Types::DOUBLE].size
+  SIZEOF_BOOL        = Fiddle::FFIBackend::FFITypes[Types::BOOL].size
+  SIZEOF_SIZE_T      = Fiddle::FFIBackend::FFITypes[Types::SIZE_T].size
   SIZEOF_SSIZE_T     = SIZEOF_SIZE_T
-  SIZEOF_PTRDIFF_T   = Fiddle::JRuby::FFITypes[Types::PTRDIFF_T].size
-  SIZEOF_INTPTR_T    = Fiddle::JRuby::FFITypes[Types::INTPTR_T].size
-  SIZEOF_UINTPTR_T   = Fiddle::JRuby::FFITypes[Types::UINTPTR_T].size
-  SIZEOF_CONST_STRING = Fiddle::JRuby::FFITypes[Types::VOIDP].size
+  SIZEOF_PTRDIFF_T   = Fiddle::FFIBackend::FFITypes[Types::PTRDIFF_T].size
+  SIZEOF_INTPTR_T    = Fiddle::FFIBackend::FFITypes[Types::INTPTR_T].size
+  SIZEOF_UINTPTR_T   = Fiddle::FFIBackend::FFITypes[Types::UINTPTR_T].size
+  SIZEOF_CONST_STRING = Fiddle::FFIBackend::FFITypes[Types::VOIDP].size
 end
diff --git a/ext/fiddle/lib/fiddle/ruby.rb b/ext/fiddle/lib/fiddle/ruby.rb
deleted file mode 100644
index ee5a9a9379..0000000000
--- a/ext/fiddle/lib/fiddle/ruby.rb
+++ /dev/null
@@ -1 +0,0 @@
-require "fiddle.so"
diff --git a/test/fiddle/helper.rb b/test/fiddle/helper.rb
index aebe028206..457e02f595 100644
--- a/test/fiddle/helper.rb
+++ b/test/fiddle/helper.rb
@@ -183,6 +183,10 @@ module Fiddle
       end
     end
 
+    def ffi_backend?
+      RUBY_ENGINE != 'ruby'
+    end
+
     def under_gc_stress
       stress, GC.stress = GC.stress, true
       yield
diff --git a/test/fiddle/test_closure.rb b/test/fiddle/test_closure.rb
index 3985e1e2bf..26cff8e516 100644
--- a/test/fiddle/test_closure.rb
+++ b/test/fiddle/test_closure.rb
@@ -58,9 +58,9 @@ module Fiddle
     end
 
     def test_const_string
-      if RUBY_ENGINE == "jruby"
+      if ffi_backend?
         omit("Closure with :const_string works but " +
-             "Function with :const_string doesn't work with JRuby")
+             "Function with :const_string doesn't work with FFI backend")
       end
 
       closure_class = Class.new(Closure) do
@@ -119,9 +119,14 @@ module Fiddle
       end
 
       require 'objspace'
+      closure_class = Class.new(Closure) do
+        def call
+          10
+        end
+      end
       n = 10000
       n.times do
-        Closure.create(:int, [:void]) do |closure|
+        closure_class.create(:int, [:void]) do |closure|
           ObjectSpace.memsize_of(closure)
         end
       end
diff --git a/test/fiddle/test_fiddle.rb b/test/fiddle/test_fiddle.rb
index b247ae15cb..28ae922171 100644
--- a/test/fiddle/test_fiddle.rb
+++ b/test/fiddle/test_fiddle.rb
@@ -6,8 +6,8 @@ end
 
 class TestFiddle < Fiddle::TestCase
   def test_nil_true_etc
-    if RUBY_ENGINE == "jruby"
-      omit("Fiddle::Q* aren't supported with JRuby")
+    if ffi_backend?
+      omit("Fiddle::Q* aren't supported with FFI backend")
     end
 
     assert_equal Fiddle::Qtrue, Fiddle.dlwrap(true)
@@ -30,6 +30,10 @@ class TestFiddle < Fiddle::TestCase
     if Dir.glob("/usr/lib/*/libncurses.so").empty?
       omit("libncurses.so is needed")
     end
+    if ffi_backend?
+      omit("Fiddle::Handle#file_name doesn't exist in FFI backend")
+    end
+
     # libncurses.so uses INPUT() on Debian GNU/Linux
     # $ cat /usr/lib/x86_64-linux-gnu/libncurses.so
     # INPUT(libncurses.so.6 -ltinfo)
@@ -44,6 +48,10 @@ class TestFiddle < Fiddle::TestCase
 
   def test_dlopen_linker_script_group_linux
     omit("This is only for Linux") unless RUBY_PLATFORM.match?("linux")
+    if ffi_backend?
+      omit("Fiddle::Handle#file_name doesn't exist in FFI backend")
+    end
+
     # libc.so uses GROUP() on Debian GNU/Linux
     # $ cat /usr/lib/x86_64-linux-gnu/libc.so
     # /* GNU ld script
diff --git a/test/fiddle/test_func.rb b/test/fiddle/test_func.rb
index 5d69cc5f11..ca503f92ad 100644
--- a/test/fiddle/test_func.rb
+++ b/test/fiddle/test_func.rb
@@ -64,6 +64,10 @@ module Fiddle
     end
 
     def test_qsort1
+      if RUBY_ENGINE == "jruby"
+        omit("The untouched sanity check is broken on JRuby: https://github.com/jruby/jruby/issues/8365")
+      end
+
       closure_class = Class.new(Closure) do
         def call(x, y)
           Pointer.new(x)[0] <=> Pointer.new(y)[0]
@@ -74,27 +78,32 @@ module Fiddle
         qsort = Function.new(@libc['qsort'],
                              [TYPE_VOIDP, TYPE_SIZE_T, TYPE_SIZE_T, TYPE_VOIDP],
                              TYPE_VOID)
-        buff = "9341"
+        untouched = "9341"
+        buff = +"9341"
         qsort.call(buff, buff.size, 1, callback)
         assert_equal("1349", buff)
 
         bug4929 = '[ruby-core:37395]'
-        buff = "9341"
+        buff = +"9341"
         under_gc_stress do
           qsort.call(buff, buff.size, 1, callback)
         end
         assert_equal("1349", buff, bug4929)
+
+        # Ensure the test didn't mutate String literals
+        assert_equal("93" + "41", untouched)
       end
     ensure
       # We can't use ObjectSpace with JRuby.
-      return if RUBY_ENGINE == "jruby"
-      # Ensure freeing all closures.
-      # See https://github.com/ruby/fiddle/issues/102#issuecomment-1241763091 .
-      not_freed_closures = []
-      ObjectSpace.each_object(Fiddle::Closure) do |closure|
-        not_freed_closures << closure unless closure.freed?
+      unless RUBY_ENGINE == "jruby"
+        # Ensure freeing all closures.
+        # See https://github.com/ruby/fiddle/issues/102#issuecomment-1241763091 .
+        not_freed_closures = []
+        ObjectSpace.each_object(Fiddle::Closure) do |closure|
+          not_freed_closures << closure unless closure.freed?
+        end
+        assert_equal([], not_freed_closures)
       end
-      assert_equal([], not_freed_closures)
     end
 
     def test_snprintf
diff --git a/test/fiddle/test_function.rb b/test/fiddle/test_function.rb
index b4b2df2874..6ec40bee06 100644
--- a/test/fiddle/test_function.rb
+++ b/test/fiddle/test_function.rb
@@ -41,6 +41,9 @@ module Fiddle
       if RUBY_ENGINE == "jruby"
         omit("rb_str_dup() doesn't exist in JRuby")
       end
+      if RUBY_ENGINE == "truffleruby"
+        omit("rb_str_dup() doesn't work with TruffleRuby")
+      end
 
       libruby = Fiddle.dlopen(nil)
       rb_str_dup = Function.new(libruby['rb_str_dup'],
@@ -109,8 +112,8 @@ module Fiddle
     end
 
     def test_last_error
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle.last_error doesn't work with JRuby")
+      if ffi_backend?
+        omit("Fiddle.last_error doesn't work with FFI backend")
       end
 
       func = Function.new(@libc['strcpy'], [TYPE_VOIDP, TYPE_VOIDP], TYPE_VOIDP)
@@ -219,6 +222,9 @@ module Fiddle
       if RUBY_ENGINE == "jruby"
         omit("rb_obj_frozen_p() doesn't exist in JRuby")
       end
+      if RUBY_ENGINE == "truffleruby"
+        omit("memory leak detection is fragile with TruffleRuby")
+      end
 
       if respond_to?(:assert_nothing_leaked_memory)
         rb_obj_frozen_p_symbol = Fiddle.dlopen(nil)["rb_obj_frozen_p"]
diff --git a/test/fiddle/test_handle.rb b/test/fiddle/test_handle.rb
index 2a51add852..e0ad17a9cb 100644
--- a/test/fiddle/test_handle.rb
+++ b/test/fiddle/test_handle.rb
@@ -9,8 +9,8 @@ module Fiddle
     include Fiddle
 
     def test_to_i
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Handle#to_i is unavailable with JRuby")
+      if ffi_backend?
+        omit("Fiddle::Handle#to_i is unavailable with FFI backend")
       end
 
       handle = Fiddle::Handle.new(LIBC_SO)
@@ -18,8 +18,8 @@ module Fiddle
     end
 
     def test_to_ptr
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Handle#to_i is unavailable with JRuby")
+      if ffi_backend?
+        omit("Fiddle::Handle#to_i is unavailable with FFI backend")
       end
 
       handle = Fiddle::Handle.new(LIBC_SO)
@@ -34,8 +34,8 @@ module Fiddle
     end
 
     def test_static_sym
-      if RUBY_ENGINE == "jruby"
-        omit("We can't assume static symbols with JRuby")
+      if ffi_backend?
+        omit("We can't assume static symbols with FFI backend")
       end
 
       begin
@@ -133,8 +133,8 @@ module Fiddle
     end
 
     def test_file_name
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Handle#file_name doesn't exist in JRuby")
+      if ffi_backend?
+        omit("Fiddle::Handle#file_name doesn't exist in FFI backend")
       end
 
       file_name = Handle.new(LIBC_SO).file_name
@@ -155,8 +155,8 @@ module Fiddle
     end
 
     def test_NEXT
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Handle::NEXT doesn't exist in JRuby")
+      if ffi_backend?
+        omit("Fiddle::Handle::NEXT doesn't exist in FFI backend")
       end
 
       begin
diff --git a/test/fiddle/test_import.rb b/test/fiddle/test_import.rb
index 26190325ec..79b65d97f5 100644
--- a/test/fiddle/test_import.rb
+++ b/test/fiddle/test_import.rb
@@ -154,8 +154,8 @@ module Fiddle
     end
 
     def test_io()
-      if RUBY_ENGINE == "jruby"
-        omit("BUILD_RUBY_PLATFORM doesn't exist in JRuby")
+      if ffi_backend?
+        omit("BUILD_RUBY_PLATFORM doesn't exist in FFI backend")
       end
 
       if( RUBY_PLATFORM != BUILD_RUBY_PLATFORM ) || !defined?(LIBC.fprintf)
diff --git a/test/fiddle/test_pointer.rb b/test/fiddle/test_pointer.rb
index ea8015438e..d46fb662ba 100644
--- a/test/fiddle/test_pointer.rb
+++ b/test/fiddle/test_pointer.rb
@@ -11,8 +11,8 @@ module Fiddle
     end
 
     def test_can_read_write_memory
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Pointer.{read,write} don't exist in JRuby")
+      if ffi_backend?
+        omit("Fiddle::Pointer.{read,write} don't exist in FFI backend")
       end
 
       # Allocate some memory
@@ -113,8 +113,8 @@ module Fiddle
     end
 
     def test_inspect
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Pointer#inspect is incompatible on JRuby")
+      if ffi_backend?
+        omit("Fiddle::Pointer#inspect is incompatible with FFI backend")
       end
 
       ptr = Pointer.new(0)
@@ -132,8 +132,8 @@ module Fiddle
     end
 
     def test_to_ptr_io
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle::Pointer.to_ptr(IO) isn't supported with JRuby")
+      if ffi_backend?
+        omit("Fiddle::Pointer.to_ptr(IO) isn't supported with FFI backend")
       end
 
       Pointer.malloc(10, Fiddle::RUBY_FREE) do |buf|
@@ -183,8 +183,8 @@ module Fiddle
     end
 
     def test_ref_ptr
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle.dlwrap([]) isn't supported with JRuby")
+      if ffi_backend?
+        omit("Fiddle.dlwrap([]) isn't supported with FFI backend")
       end
 
       ary = [0,1,2,4,5]
@@ -195,8 +195,8 @@ module Fiddle
     end
 
     def test_to_value
-      if RUBY_ENGINE == "jruby"
-        omit("Fiddle.dlwrap([]) isn't supported with JRuby")
+      if ffi_backend?
+        omit("Fiddle.dlwrap([]) isn't supported with FFI backend")
       end
 
       ary = [0,1,2,4,5]