Creating database with small mapsize produces segfault

[canadaduane]

$ mkdir lmdb
$ irb -rlmdb
irb(main):001:0> LMDB.new('lmdb', mapsize: 1000)
(irb):1: [BUG] Segmentation fault at 0x00000103a20090
ruby 2.1.3p242 (2014-09-19 revision 47630) [x86_64-darwin13.0]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/CrashReporter
     * /Library/Logs/CrashReporter
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.

-- Control frame information -----------------------------------------------
c:0019 p:---- s:0077 e:000076 CFUNC  :new
c:0018 p:0019 s:0072 e:000071 EVAL   (irb):1 [FINISH]
c:0017 p:---- s:0070 e:000069 CFUNC  :eval
c:0016 p:0024 s:0063 e:000062 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/workspace.rb:86
c:0015 p:0025 s:0056 e:000054 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/context.rb:380
c:0014 p:0022 s:0050 e:000049 BLOCK  /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:492
c:0013 p:0040 s:0042 e:000041 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:624
c:0012 p:0009 s:0037 e:000036 BLOCK  /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:489
c:0011 p:0118 s:0033 e:000032 BLOCK  /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:247 [FINISH]
c:0010 p:---- s:0030 e:000029 CFUNC  :loop
c:0009 p:0007 s:0027 e:000026 BLOCK  /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:233 [FINISH]
c:0008 p:---- s:0025 e:000024 CFUNC  :catch
c:0007 p:0015 s:0021 e:000020 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:232
c:0006 p:0030 s:0018 E:001308 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:488
c:0005 p:0008 s:0015 e:000014 BLOCK  /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:397 [FINISH]
c:0004 p:---- s:0013 e:000012 CFUNC  :catch
c:0003 p:0143 s:0009 E:0015e8 METHOD /Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:396
c:0002 p:0021 s:0004 E:001cf8 EVAL   /Users/duane/.rbenv/versions/2.1.3/bin/irb:11 [FINISH]
c:0001 p:0000 s:0002 E:002058 TOP    [FINISH]

/Users/duane/.rbenv/versions/2.1.3/bin/irb:11:in `<main>'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:396:in `start'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:396:in `catch'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:397:in `block in start'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:488:in `eval_input'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:232:in `each_top_level_statement'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:232:in `catch'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:233:in `block in each_top_level_statement'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:233:in `loop'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/ruby-lex.rb:247:in `block (2 levels) in each_top_level_statement'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:489:in `block in eval_input'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:624:in `signal_status'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb.rb:492:in `block (2 levels) in eval_input'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/context.rb:380:in `evaluate'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/workspace.rb:86:in `evaluate'
/Users/duane/.rbenv/versions/2.1.3/lib/ruby/2.1.0/irb/workspace.rb:86:in `eval'
(irb):1:in `irb_binding'
(irb):1:in `new'

-- C level backtrace information -------------------------------------------
0   ruby                                0x00000001033eb656 rb_vm_bugreport + 134
1   ruby                                0x00000001032a00e3 report_bug + 307
2   ruby                                0x000000010329ffa4 rb_bug + 180
3   ruby                                0x000000010336e109 sigsegv + 153
4   libsystem_platform.dylib            0x00007fff943e15aa _sigtramp + 26
5   lmdb_ext.bundle                     0x00000001036fd10f mdb_env_pick_meta + 31
6   ???                                 0x00007fff5c99b830 0x0 + 140734746966064

[vjoel]

Not getting that here:

$ irb -r lmdb
>> LMDB.new('lmdb', mapsize: 1000)
=> #<LMDB::Environment:0x007fa6daf21420>

ruby 2.1.3p242 (2014-09-19 revision 47630) [x86_64-linux]
Linux smeg 3.13.0-36-generic #63-Ubuntu SMP Wed Sep 3 21:30:07 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) 

Did you do anything special to install liblmdb separately from the gem, or did you install only the gem (which should be fine)?

[canadaduane]

I didn't install liblmdb separately, just through the gem.

Also, I installed the gem on a 2nd Mac OS X system and received the same result.

Did you try creating an empty directory first? I get two different results (although, not the same as yours) depending on the state of the dir:

$ mkdir db  # <-- empty dir
$ irb -rlmdb
irb(main):001:0> db = LMDB.new('db', mapsize: 1000)
(irb):1: [BUG] Segmentation fault
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-darwin12.2.0]
# ... etc ...

$ rm -rf db
$ irb -rlmdb
irb(main):001:0> LMDB.new('db', mapsize: 1000)
LMDB::Error: No such file or directory
    from (irb):1:in `new'
    from (irb):1
    from /Users/duane/.rbenv/versions/1.9.3-p194/bin/irb:12:in `<main>'

[vjoel]

The second error is expected. LMDB.new doesn't try to create a directory.

Are you seeing similar errors with larger mapsize values? The default is 1MB.

[canadaduane]

Not for very large sizes. I tried several sizes, though, and it looks like 4100 is the smallest size I can go without a segfault.

Maybe we're hitting a 4096 byte bug?

lmdb_test.rb:

require 'fileutils'

size = 1_000_000

while size > 0
  FileUtils.rm_rf 'db'
  FileUtils.mkdir 'db'
  puts size
  db = LMDB.new('db', mapsize: size)
  db.close
  size -= 100
end

Running with ruby -rlmdb lmdb_test.rb:

# ...
5000
4900
4800
4700
4600
4500
4400
4300
4200
4100
4000
lmdb_test.rb:9: [BUG] Segmentation fault
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-darwin12.2.0]

-- Control frame information -----------------------------------------------
c:0004 p:---- s:0013 b:0013 l:000012 d:000012 CFUNC  :new
c:0003 p:0100 s:0008 b:0008 l:001dc8 d:001728 EVAL   lmdb_test.rb:9
c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
c:0001 p:0000 s:0002 b:0002 l:001dc8 d:001dc8 TOP   

[vjoel]

Maybe it's a bug of MDB specific to osx?

Can you recreate this with a C program?

[canadaduane]

It's certainly possible. I don't have the time to work further on this, but
thanks for your help.
On Oct 3, 2014 5:03 PM, "Joel VanderWerf" notifications@github.com wrote:

Maybe it's a bug of MDB specific to osx?

Can you recreate this with a C program?

—
Reply to this email directly or view it on GitHub
#36 (comment).

[richardgolding]

One possible clue: the page size on OS X is 4k.

-r

On Oct 3, 2014, at 6:54 PM, Duane Johnson notifications@github.com wrote:

It's certainly possible. I don't have the time to work further on this, but
thanks for your help.
On Oct 3, 2014 5:03 PM, "Joel VanderWerf" notifications@github.com wrote:

Maybe it's a bug of MDB specific to osx?

Can you recreate this with a C program?

—
Reply to this email directly or view it on GitHub
#36 (comment).

—
Reply to this email directly or view it on GitHub.