From: Paul C <paul_c@...>
Date: 2001-03-14T05:40:02+09:00
Subject: [ruby-talk:12580] Re: Strange segmentation fault problem with C++ extension - the plot thickens


Having played around a but more it looks like the behaviour of the module
when called within a begin/rescue block is a somewhat more complex that I
had described earlier and depending on context I can get a segmentation
fault in either ruby or IRB

Some of the calling sequences I have tried are shown below.

As far as I can work out the symptoms are -

In Ruby:
    - The sequence {ok-fail-ok} works ok within a block context
    - The sequence {ok-fail-ok-ok} causes a segmentation fault
    - Multiple sequences of {ok-fail} in separate blocks are ok
    - Multiple sequences of {ok-fail-ok} cause a segmentation fault

In IRB:
    - The sequence {ok-fail-ok} within a block always causes a segmentation
fault
    - Multiple repetitions of an {ok-fail} are ok

Also if I replace the 'raise' in the offending function with a 'return Qnil'
all the problems go away.

I am fairly sure that I have some sort of loose pointer in the code which
gets reset with the block context however I havent been able to track
anything down yet.

Apologies for the length of the post and thanks in advance for everybodies
help

Regards, Paul



==== test_ok.rb

:   require 'Zip'
:   z = Zip::ZipFile.new "test.zip"
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "zzzzzz"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end

# ruby test_ok.rb -> OK
# irb test_ok.rb -> Segmentation Fault

==== test_ok2.rb

:   require 'Zip'
:   z = Zip::ZipFile.new "test.zip"
:
:   5.times {
:       begin
:           entry = z.entry "extconf.rb"
:           print entry.inspect, "\n"
:       rescue RuntimeError => err
:           print "Caught Exception: #{err}\n"
:       end
:
:       begin
:           entry = z.entry "zzzzz"
:           print entry.inspect, "\n" #fails
:       rescue RuntimeError => err
:           print "Caught Exception: #{err}\n"
:       end
:   }

# ruby test_ok2.rb -> OK
# irb test_ok2.rb -> OK

==== test_ok3.rb

:   require 'Zip'
:   z = Zip::ZipFile.new "test.zip"
:
:   ["extconf.rb","zzzzzz"].each { |e|
:       begin
:           entry = z.entry e
:           print entry.inspect, "\n"
:       rescue RuntimeError => err
:           print "Caught Exception: #{err}\n"
:       end
:   }
:
:   ["extconf.rb","zzzzzz"].each { |e|
:       begin
:           entry = z.entry e
:           print entry.inspect, "\n"
:       rescue RuntimeError => err
:           print "Caught Exception: #{err}\n"
:       end
:   }

# ruby test_ok3.rb -> OK
# irb test_ok3.rb -> Segmentation Fault


# ruby test_ok3.rb -> OK
# irb test_ok3.rb -> Segmentation Fault

==== test_fail.rb

:   require 'Zip'
:   z = Zip::ZipFile.new "test.zip"
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "zzzzzz"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entryntry = z.entry "extconf.rb"
:       print entryntry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end

# ruby test_fail.rb -> Segmentation Fault
# irb test_fail.rb -> Segmentation Fault

==== test_fail2.rb

:require 'Zip'
:
:z = Zip::ZipFile.new "test.zip"
:
:5.times {
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "zzzzz"
:       print entry.inspect, "\n" #fails
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   begin
:       entry = z.entry "extconf.rb"
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:}

# ruby test_fail2.rb -> Segmentation Fault
# irb test_fail2.rb -> Segmentation Fault

==== test_fail3.rb

:   require 'Zip'
:   z = Zip::ZipFile.new "test.zip"
:
:   ["extconf.rb","zzzzzz","extconf.rb"].each { |e|
:
:   begin
:       entry = z.entry e
:       print entry.inspect, "\n"
:   rescue RuntimeError => err
:       print "Caught Exception: #{err}\n"
:   end
:
:   }

# ruby test_fail3.rb -> Segmentation Fault
# irb test_fail3.rb -> Segmentation Fault