From: Asher Haig <redmine@...>
Date: 2010-07-11T17:44:51+09:00
Subject: [ruby-core:31186] [Bug #3558] Passing args with rb_block_call

Bug #3558: Passing args with rb_block_call
http://redmine.ruby-lang.org/issues/show/3558

Author: Asher Haig
Status: Open, Priority: High
Category: core
ruby -v: 1.9.2rc1

I've posted in two places about this over the past 2 days, and today I've taken a look through the internals and I am fairly sure that I am looking at a bug. 

Last post here: http://www.ruby-forum.com/topic/212893#new
And originally I posted here: http://stackoverflow.com/questions/3217624/ruby-1-9-1-p378-c-extension-rb-block-call-weirdness

The short of the problem is that when I call rb_block_call, the called block
function receives the yield value and data2 appropriately, but argc is
always set at 1 (no matter what I pass) while argv[ 0 ] and argv[ 2 ] ==
yield value, and argv[ 1 ] == Qfalse.

So far as I can tell from looking at the internals (primarily invoke_block_from_c and vm_yield_with_cfunc), no handling is being done for the args that were passed to rb_block_call. Instead, the specified function gets argc/argv from rb_yield, which is always 1 and the value from rb_yield. 

There are only three examples that I see in the Ruby source that use rb_block_call while passing args: one in Enumerator, and two in Range. The method signatures there provided me additional confusion (VALUE i, void* args), as it does not match the description of expected functions. Presumably it still works since it ends with the void pointer, which is being used for variable args. 

Asher


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