• Joseph Rushton Wakeling (118/118) May 01 2017 Hello all :-)

Joseph Rushton Wakeling <joseph.wakeling webdrake.net> writes:

Hello all :-)

Stable snap packages for LDC 1.2.0 have been available since 
before the official 1.2.0 release announcement 1 week ago.  
However, since there's more than just the availability of the 
packages to announce, I thought I'd write up some notes for the 
forums.

Please report any issues using the package here:
https://github.com/ldc-developers/ldc2.snap

Enjoy, and please do let me know how you get on if you try these 
packages :-)

Thanks & best wishes,

     -- Joe


What are snap packages?
-----------------------

Snaps are one of a number of next-gen packaging schemes that are 
designed to provide secure, containerized applications in a 
distro-neutral manner.  A good general overview is provided on 
the main project website: https://snapcraft.io/

In practice, this means that the LDC snap package provides a 
reliable way to install LDC on multiple different distros.

The LDC snap package is a 'classic' snap, meaning that its 
confinement rules allow access to the host system in order to 
access e.g. the host compiler toolchain, and development 
libraries installed using the regular host package manager.  More 
information on classic snaps is available here:
https://insights.ubuntu.com/2017/01/09/how-to-snap-introducing-classic-confinement/
https://snapcraft.io/docs/reference/confinement


Installing
----------

It should be possible to install snap packages on any distro with 
a sufficiently up to date version of the `snapd` daemon (which 
manages both installing and running these packages).  
Installation instructions for different distros are available 
here:
https://snapcraft.io/docs/core/install

Once snapd is installed, log off and back on again to make sure 
that your PATH environment variable is set to include the 
location of any installed snap applications.  Then, to install 
the LDC snap:

     sudo snap install --classic ldc2

Alternatively, on systems not supporting `sudo`, just run the 
`snap install ...` command as root.

The `--classic` flag is necessary in order to grant permission 
for the classic confinement used by the snap (see above).

The `ldc2` snap package is currently available for i386 and amd64 
architectures, with plans to add more supported architectures 
over time.

The installed package will auto-update over time, but can be 
manually updated by running:

     sudo snap refresh ldc2

The snap package makes available not only the `ldc2` compiler 
itself but also the DMD-alike `ldmd2` compiler interface, and the 
`ldc-profdata` and `ldc-prune-cache` tools.  By default these can 
be run using the command `ldc2.command`, e.g. `ldc2.ldmd2`.  This 
namespacing helps to avoid clashes between snap commands.  
However, the package also defines aliases that allow for use of 
the regular commands.  For example:

     sudo snap alias ldc2 ldmd2

will enable the `ldmd2` alias, allowing the `ldmd2` command to be 
used directly instead of `ldc2.ldmd2`.  Type:

     snap aliases

for a complete list of the available aliases, and which ones are 
currently enabled.

The command

     snap list

can be used to list all currently installed snap packages, while

     snap info [name]

will give information on a specific snap package (whether 
installed or not); so e.g. `snap info ldc2` will give you 
information on the LDC snap package.


Running
-------

The compiler can be invoked using the normal `ldc2` and `ldmd2` 
commands (although see above regarding aliases if you want to use 
`ldmd2`).  It uses the host system's C compiler for linking, so 
on most Linux distros it will require GCC to be installed.


Tracks and channels
-------------------

The snap store allows multiple different versions of the snap 
package to be made available on user demand: 
https://snapcraft.io/docs/reference/channels

In brief, snap packages are distributed via channels, named 
`edge`, `beta`, `candidate` and `stable`.  By default packages 
are installed from `stable`, but it is possible to request 
installation (and updates) from one of the other channels, e.g.:

     sudo snap refresh --candidate ldc2

will ensure that you have the latest version installed from the 
`candidate` channel, and that updates will be installed from that 
channel instead of `stable`.

In addition, the snap store also defines release _tracks_, which 
are used to define long-term-support release versions.  For 
example, if you want to guarantee you are installing from the 
1.2.x release series of LDC, you can type:

     sudo snap install --classic --channel=1.2/stable ldc2

or, to switch to tracking that track and channel:

     sudo snap refresh --channel=1.2/stable

New tracks will be defined for each new minor release series of 
LDC: for example, a 1.3 track is already defined in preparation 
for the upcoming 1.3.0 release.

Without any specific requirements, it is recommended to just 
install from the `stable` channel (with no track specified), as 
this will keep you up to date with the latest stable LDC 
releases.  However, you can use the choice of track to ensure 
that you only receive updates for a given minor release series of 
LDC.  Alternatively, you can switch between tracks and channels 
as needed, if you want to try out different versions of the 
compiler.

Known issues
------------

Given the current state of `snapd` support in distros, the `ldc2` 
snap package is expected to work on:

   * Ubuntu 14.04, 16.04, 16.10 and 17.04 (and current development 
versions)

   * Debian Testing and Unstable

   * OpenSUSE Leap

Link-time optimization (the `-flto=full` option) is not expected 
to work on Ubuntu 14.04 or on OpenSUSE, but should work fine on 
Debian and on later Ubuntu releases.