Issue #9009 has been reported by yekka (Nikolay Bozhenov).

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Bug #9009: Wrong binding when tracing c-calls
https://bugs.ruby-lang.org/issues/9009

Author: yekka (Nikolay Bozhenov)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.1.0dev (2013-10-04 trunk 43141) [x86_64-linux]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


When I use set_trace_func to trace ruby code, I get a wrong binding in
case of c-calls. In this case binding.eval("self") is not the receiver
of the call. Whereas in case of ruby-calls binding.eval("self") yields
the receiver of the call.
The underlying problem is that c-calls aren't pushed onto the frame stack.
It seems that currently there is no way to find out the receiver of c-call
inside tracing function.

Example of code:

$ cat test.rb
class IO
    def some_method
    end
end

puts "true receiver is #{$stdout}\n\n"

set_trace_func proc { |event, file, line, id, binding, classname|
    if event == "call" or event == "c-call"
        puts "#{event} #{id}:"
        puts "\tapparent receiver = #{binding.eval("self")}"
        puts "\tbacktrace:"
        caller.each { |l| puts "\t\t#{l}" }
        puts
    end
}

$stdout.write ""      # c-call
$stdout.some_method   # ruby-call


Execution:
  
$ ruby test.rb 
true receiver is #<IO:0x00000000bed2a0>

c-call write:
        apparent receiver = main
        backtrace:
                test.rb:18:in `<main>'

call some_method:
        apparent receiver = #<IO:0x00000000bed2a0>
        backtrace:
                test.rb:2:in `some_method'
                test.rb:19:in `<main>'


Expected result:                

true receiver is #<IO:0x00000000bed2a0>

c-call write:
        apparent receiver = #<IO:0x00000000bed2a0>
        backtrace:
                somewhere:in `write'
                test.rb:18:in `<main>'

call some_method:
        apparent receiver = #<IO:0x00000000bed2a0>
        backtrace:
                test.rb:2:in `some_method'
                test.rb:19:in `<main>'



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