merge revision(s) 0eb634ae73cb327ede833b72492f912792a4a9d5: [Backport #19464]

	YJIT: Detect and reject `send(:alias_for_send, :foo)`

	Previously, YJIT failed to put the stack into the correct shape when
	`BasicObject#send` calls an alias method for the send method itself.
	This can manifest as strange `NoMethodError`s in the final non-send
	receiver, as [seen][1] with the kt-paperclip gem. I also found a case
	where it makes YJIT fail the stack size assertion while compiling
	`leave`.

	YJIT's `BasicObject#__send__` implementation already rejects sends to
	`send`, but didn't detect sends to aliases of `send`. Adjust the
	detection and reject these cases.

	Fixes [Bug #19464]

	[1]: https://github.com/Shopify/yjit/issues/306
	---
	 test/ruby/test_yjit.rb | 20 ++++++++++++++++++++
	 yjit/src/codegen.rs    | 25 ++++++++++---------------
	 2 files changed, 30 insertions(+), 15 deletions(-)

3 files changed, 31 insertions, 16 deletions

diff --git a/test/ruby/test_yjit.rb b/test/ruby/test_yjit.rb
index 2ea915bc0d..e4080595b0 100644
--- a/test/ruby/test_yjit.rb
+++ b/test/ruby/test_yjit.rb
@@ -1121,6 +1121,26 @@ class TestYJIT < Test::Unit::TestCase
     RUBY
   end
 
+  def test_nested_send
+    #[Bug #19464]
+    assert_compiles(<<~RUBY, result: [:ok, :ok])
+      klass = Class.new do
+        class << self
+          alias_method :my_send, :send
+
+          def bar = :ok
+
+          def foo = bar
+        end
+      end
+
+      with_break = -> { break klass.send(:my_send, :foo) }
+      wo_break = -> { klass.send(:my_send, :foo) }
+
+      [with_break[], wo_break[]]
+    RUBY
+  end
+
   private
 
   def code_gc_helpers
diff --git a/version.h b/version.h
index 75e081cf3c..5eb9d00160 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 1
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 39
+#define RUBY_PATCHLEVEL 40
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"
diff --git a/yjit/src/codegen.rs b/yjit/src/codegen.rs
index 8c5b413286..687205e10f 100644
--- a/yjit/src/codegen.rs
+++ b/yjit/src/codegen.rs
@@ -5822,7 +5822,6 @@ fn gen_send_general(
                 let opt_type = unsafe { get_cme_def_body_optimized_type(cme) };
                 match opt_type {
                     OPTIMIZED_METHOD_TYPE_SEND => {
-
                         // This is for method calls like `foo.send(:bar)`
                         // The `send` method does not get its own stack frame.
                         // instead we look up the method and call it,
@@ -5830,6 +5829,16 @@ fn gen_send_general(
 
                         let starting_context = ctx.clone();
 
+                        // Reject nested cases such as `send(:send, :alias_for_send, :foo))`.
+                        // We would need to do some stack manipulation here or keep track of how
+                        // many levels deep we need to stack manipulate. Because of how exits
+                        // currently work, we can't do stack manipulation until we will no longer
+                        // side exit.
+                        if flags & VM_CALL_OPT_SEND != 0 {
+                            gen_counter_incr!(asm, send_send_nested);
+                            return CantCompile;
+                        }
+
                         if argc == 0 {
                             gen_counter_incr!(asm, send_send_wrong_args);
                             return CantCompile;
@@ -5856,20 +5865,6 @@ fn gen_send_general(
                             return CantCompile;
                         }
 
-                        // We aren't going to handle `send(send(:foo))`. We would need to
-                        // do some stack manipulation here or keep track of how many levels
-                        // deep we need to stack manipulate
-                        // Because of how exits currently work, we can't do stack manipulation
-                        // until we will no longer side exit.
-                        let def_type = unsafe { get_cme_def_type(cme) };
-                        if let VM_METHOD_TYPE_OPTIMIZED = def_type {
-                            let opt_type = unsafe { get_cme_def_body_optimized_type(cme) };
-                            if let OPTIMIZED_METHOD_TYPE_SEND = opt_type {
-                                gen_counter_incr!(asm, send_send_nested);
-                                return CantCompile;
-                            }
-                        }
-
                         flags |= VM_CALL_FCALL | VM_CALL_OPT_SEND;
 
                         assume_method_lookup_stable(jit, ocb, cme);