sprintf.c: don't raise "too many arguments" errors when $DEBUG is set

[Feature #22136]

This is as far as I can tell the only method that changes its behavior
in debug mode, and that's all but helpful because it might cause
the program to abort.

Usually when you run a program with $DEBUG set, it is to find some
error that may have been swallowed, so aside from the extra output
you would expect Ruby to behave the same than in normal mode.

spec/ruby/core/string/modulo_spec.rb

@@ -67,18 +67,20 @@ describe "String#%" do
     end
   end
 
-  it "raises an ArgumentError for unused arguments when $DEBUG is true" do
-    begin
-      old_debug = $DEBUG
-      $DEBUG = true
-      s = $stderr
-      $stderr = IOStub.new
+  ruby_version_is ""..."4.1" do
+    it "raises an ArgumentError for unused arguments when $DEBUG is true" do
+      begin
+        old_debug = $DEBUG
+        $DEBUG = true
+        s = $stderr
+        $stderr = IOStub.new
 
-      -> { "" % [1, 2, 3]   }.should.raise(ArgumentError)
-      -> { "%s" % [1, 2, 3] }.should.raise(ArgumentError)
-    ensure
-      $DEBUG = old_debug
-      $stderr = s
+        -> { "" % [1, 2, 3]   }.should.raise(ArgumentError)
+        -> { "%s" % [1, 2, 3] }.should.raise(ArgumentError)
+      ensure
+        $DEBUG = old_debug
+        $stderr = s
+      end
     end
   end
 

sprintf.c

@@ -947,7 +947,6 @@ rb_str_format(int argc, const VALUE *argv, VALUE fmt)
      */
     if (posarg >= 0 && nextarg < argc && !(argc == 2 && RB_TYPE_P(argv[1], T_HASH))) {
         const char *mesg = "too many arguments for format string";
-        if (RTEST(ruby_debug)) rb_raise(rb_eArgError, "%s", mesg);
         if (RTEST(ruby_verbose)) rb_warn("%s", mesg);
     }
     rb_str_resize(result, blen);