Merge pull request #57 from sue445/doc-variable-length-arguments

Write doc

Author: sue445

CONTRIBUTING.md

@@ -1,5 +1,14 @@
 # Contribution Guide
 ## Add wrapper function for C
+### :warning: Limitation
+Go variable-length arguments cannot be passed directly to C functions
+
+e.g. `void rb_raise(VALUE exc, const char *fmt, ...)`
+
+To avoid this problem, we need to call the C function without variable-length arguments
+
+See `RbRaise` implementation in [ruby-internal-error.go](ruby-internal-error.go) for details
+
 ### 1. Generate skeleton
 Run `ruby _scripts/dump_ruby_c_functions.rb`
 

README.md

@@ -190,7 +190,7 @@ ref. https://docs.ruby-lang.org/ja/latest/function/index.html
 * [ ] `rb_frame_last_func`
 * [ ] `rb_free_generic_ivar`
 * [ ] `rb_frozen_class_p`
-* [ ] `rb_funcall`
+* ~~[ ] `rb_funcall`~~ Go's variable-length arguments couldn't be passed directly to C. See [CONTRIBUTING.md](CONTRIBUTING.md)
 * [x] `rb_funcall2`
 * [ ] `rb_funcall3`
 * [x] `rb_funcallv`