Mode=777 not respected in compose tmpfs:

My docker-compose.yml file has:

version: "2"
       - /src/core/build:exec,mode=777

but the mode of the directory is still 755. It’s interesting that mount still shows:

tmpfs on /src/core/build type tmpfs (rw,nosuid,nodev,relatime,mode=777)

but ls shows:

ls -ld /src/core/build
drwxr-xr-x 2 root root 40 Jul  1 18:31 /src/core/build

/src/core is mounted from outside the container/image

ps. docker is 1.11.2, compose is 1.7.1, on ArchLinux host

Its right 1777 for you.
From official documentation:

tmpfs-mode File mode of the tmpfs in octal. For instance, 700 or 0770. Defaults to 1777 or world-writable.