[pkg-gnupg-maint] Bug#787781: gnupg-agent: broken pipe error when a program using agent is invoked by stdbuf -oL

[nfb]

Package: gnupg-agent
Version: 2.0.27-2
Severity: normal

Hi,
i have a script that uses pass [0] password manager, which on his hand
uses gpg-agent to remember the master passphrase, as you can see.
Also i have to filter its output, so i pipe it into another script,
but since i want the output to be unbuffered to get a more real-time
feedback, i tried calling it this way:

stdbuf -oL pass <pass_arguments>

which buffers on a per line basis. On my x86 pc everything is fine,
while on my arm device i get:

gpg: error writing to `-': Broken pipe
gpg: handle plaintext failed: Broken pipe

but after that the script works as expected.
So i was wondering if any tool using gpg-agent invoked with stdbuf
with '-oL' option gives this error. I tried using '-o0' instead of
'-oL' as stdbuf option, and this gives no problems. I also tried
doing some symmetric encryptions/decriptions (not involving gpg-agent)
to make sure the issue was on the agent side, invoking every time gpg
with stdbuf, and indeed no error is showed when the agent is not used.


P.S.:
I really didn't know if this issue had the requisites to be reported
as bug, so forgive me in case it's not, or let me know if more details
are needed.


[0] http://www.passwordstore.org



-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: armhf (armv7l)

Kernel: Linux 3.8.11 (SMP w/2 CPU cores)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gnupg-agent depends on:
ii  libassuan0                  2.2.1-1
ii  libc6                       2.19-18
ii  libgcrypt20                 1.6.3-2
ii  libgpg-error0               1.17-3
ii  libpth20                    2.0.7-20
ii  libreadline6                6.3-8+b3
ii  pinentry-curses [pinentry]  0.9.2-1

Versions of packages gnupg-agent recommends:
ii  gnupg   1.4.19-3
ii  gnupg2  2.0.27-2

gnupg-agent suggests no packages.

-- no debconf information