Fix arity checking and NULL arguments to rb_scan_args to match MRI.

Author: aardvark179

lib/cext/include/truffleruby/truffleruby.h

@@ -228,6 +228,8 @@ MUST_INLINE int rb_tr_scan_args(int argc, VALUE *argv, const char *format, VALUE
   const char *formatp = format;
   int pre = 0;
   int optional = 0;
+  int n_mand = 0;
+  int n_opt = 0;
   bool rest;
   int post = 0;
   bool kwargs;
@@ -281,6 +283,9 @@ MUST_INLINE int rb_tr_scan_args(int argc, VALUE *argv, const char *format, VALUE
     rb_raise(rb_eArgError, "not enough arguments for required");
   }
 
+  n_mand = pre + post;
+  n_opt = optional;
+
   // Read arguments
 
   int argn = 0;
@@ -360,26 +365,30 @@ MUST_INLINE int rb_tr_scan_args(int argc, VALUE *argv, const char *format, VALUE
     // Don't assign the correct v to a temporary VALUE* and then assign arg to it - this doesn't optimise well
 
     switch (valuen) {
-      case 1: *v1 = arg; break;
-      case 2: *v2 = arg; break;
-      case 3: *v3 = arg; break;
-      case 4: *v4 = arg; break;
-      case 5: *v5 = arg; break;
-      case 6: *v6 = arg; break;
-      case 7: *v7 = arg; break;
-      case 8: *v8 = arg; break;
-      case 9: *v9 = arg; break;
-      case 10: *v10 = arg; break;
+    case 1: if (v1 != NULL) { *v1 = arg; } break;
+    case 2: if (v2 != NULL) { *v2 = arg; } break;
+    case 3: if (v3 != NULL) { *v3 = arg; } break;
+    case 4: if (v4 != NULL) { *v4 = arg; } break;
+    case 5: if (v5 != NULL) { *v5 = arg; } break;
+    case 6: if (v6 != NULL) { *v6 = arg; } break;
+    case 7: if (v7 != NULL) { *v7 = arg; } break;
+    case 8: if (v8 != NULL) { *v8 = arg; } break;
+    case 9: if (v9 != NULL) { *v9 = arg; } break;
+    case 10: if (v10 != NULL) { *v10 = arg; } break;
     }
 
     valuen++;
   }
 
   if (found_kwargs) {
-    return argc - 1;
-  } else {
-    return argc;
+    argc = argc - 1;
   }
+
+  if (argn < argc) {
+	rb_error_arity(argc, pre, rest ? UNLIMITED_ARGUMENTS : pre + optional);
+  }
+
+  return argc;
 }
 
 #if defined(__cplusplus)

spec/ruby/optional/capi/util_spec.rb

@@ -23,6 +23,10 @@
       lambda { @o.rb_scan_args([1, 2], "3", 0, @acc) }.should raise_error(ArgumentError)
     end
 
+    it "raises an ArgumentError if there are too many arguments" do
+      lambda { @o.rb_scan_args([1, 2, 3, 4], "3", 0, @acc) }.should raise_error(ArgumentError)
+    end
+
     it "assigns the required and optional arguments scanned" do
       @o.rb_scan_args([1, 2], "11", 2, @acc).should == 2
       ScratchPad.recorded.should == [1, 2]

src/main/c/cext/ruby.c

@@ -3468,6 +3468,27 @@ VALUE rb_enum_values_pack(int argc, const VALUE *argv) {
   rb_tr_error("rb_enum_values_pack not implemented");
 }
 
+static inline VALUE
+rb_arity_error_new(int argc, int min, int max)
+{
+    VALUE err_mess = 0;
+    if (min == max) {
+	err_mess = rb_sprintf("wrong number of arguments (given %d, expected %d)", argc, min);
+    }
+    else if (max == UNLIMITED_ARGUMENTS) {
+	err_mess = rb_sprintf("wrong number of arguments (given %d, expected %d+)", argc, min);
+    }
+    else {
+	err_mess = rb_sprintf("wrong number of arguments (given %d, expected %d..%d)", argc, min, max);
+    }
+    return rb_exc_new3(rb_eArgError, err_mess);
+}
+
+NORETURN(void rb_error_arity(int argc, int min, int max))
+{
+    rb_exc_raise(rb_arity_error_new(argc, min, max));
+}
+
 void rb_error_untrusted(VALUE obj) {
   rb_tr_error("rb_error_untrusted not implemented");
 }