File.stat.writable? returning false in JRuby, true in MRI

[duncan-bayne]

Environment

• jruby 9.1.7.0 (2.3.1) 2017-01-11 68056ae OpenJDK 64-Bit Server VM 25.192-b26 on 1.8.0_192-b26 +jit [freebsd-x86_64]
• FreeBSD x220 12.0-RELEASE FreeBSD 12.0-RELEASE r341666 GENERIC amd64

Expected Behavior

I expect JRuby and MRI Ruby to return the same value - true - when File.stat.writable? is run on a writable directory (/tmp).

Actual Behavior

JRuby returns false, where MRI returns true:

➜  ~ ls -lad /tmp
drwxrwxrwt  21 root  wheel  1024  4 Mar 09:43 /tmp
➜  ~ RBENV_VERSION=2.5.1 irb
irb(main):001:0> File.stat('/tmp').writable?
=> true

➜  ~ ls -lad /tmp
drwxrwxrwt  21 root  wheel  1024  4 Mar 09:43 /tmp
➜  ~ RBENV_VERSION=jruby-9.1.7.0 irb
irb(main):001:0> File.stat('/tmp').writable?
=> false

This is causing many failures, including an inability to install Gems, because Dir::tmpdir is failing to find a writable tmpdir.

[duncan-bayne]

truss suggests the call to fstatat is returning the correct permissions:

fstatat(AT_FDCWD,"/tmp",{ mode=drwxrwxrwt ,inode=15328896,size=1024,blksize=32768 },0x0) = 0 (0x0)

[Freaky]

See #5521 - until jnr/jnr-posix#126 is fixed, you'll want to run JRuby under an 11.2 chroot or jail so it sees the old stat structure.

[headius]

@Freaky Sorry that jnr/jnr-posix#126 got left behind. Let's get it merged and fix this!

[enebo]

jnr-posix was updated so this is fixed.

[Freaky]

Hmm, just ran a build off latest jruby-master, and I'm not seeing this issue resolved despite it apparently using jnr-posix 3.0.50 which should have my fix.

I'd be expecting it to call out to /bin/freebsd-version to determine the appropriate ABI, but I'm not seeing that with ktrace...

[Freaky]

Disregard that, I was holding it wrong. Ahem.