[ruby/fiddle] windows: add Fiddle.win32_last_socket_error{,=}

GitHub: fix GH-72

Users can't use WSAGetLastError() with Ruby 3.0 or later because
rb_funcall() resets the last socket error internally.

Users can get the last socket error by Fiddle.win32_last_socket_error.

Reported by Kentaro Hayashi. Thanks!!!

76158db00a

ext/fiddle/function.c

@@ -375,10 +375,17 @@ function_call(int argc, VALUE argv[], VALUE self)
         (void)rb_thread_call_without_gvl(nogvl_ffi_call, &args, 0, 0);
     }
 
-    rb_funcall(mFiddle, rb_intern("last_error="), 1, INT2NUM(errno));
+    {
+        int errno_keep = errno;
 #if defined(_WIN32)
-    rb_funcall(mFiddle, rb_intern("win32_last_error="), 1, INT2NUM(errno));
+        int socket_error = WSAGetLastError();
+        rb_funcall(mFiddle, rb_intern("win32_last_error="), 1,
+                   INT2NUM(errno_keep));
+        rb_funcall(mFiddle, rb_intern("win32_last_socket_error="), 1,
+                   INT2NUM(socket_error));
 #endif
+        rb_funcall(mFiddle, rb_intern("last_error="), 1, INT2NUM(errno_keep));
+    }
 
     ALLOCV_END(alloc_buffer);
 

ext/fiddle/lib/fiddle.rb

@@ -17,6 +17,18 @@ module Fiddle
     def self.win32_last_error= error
       Thread.current[:__FIDDLE_WIN32_LAST_ERROR__] = error
     end
+
+    # Returns the last win32 socket +Error+ of the current executing
+    # +Thread+ or nil if none
+    def self.win32_last_socket_error
+      Thread.current[:__FIDDLE_WIN32_LAST_SOCKET_ERROR__]
+    end
+
+    # Sets the last win32 socket +Error+ of the current executing
+    # +Thread+ to +error+
+    def self.win32_last_socket_error= error
+      Thread.current[:__FIDDLE_WIN32_LAST_SOCKET_ERROR__] = error
+    end
   end
 
   # Returns the last +Error+ of the current executing +Thread+ or nil if none