Suppose I want to use different versions of GHC, each of them with a different binary name.
Question 1. Can I use ./configure --prefix=ghc-some-version-dir for each of the installations and create symbolic links ghc-7.4.1, ghc-7.6.2, ghc-head without problems?
That is, after the installation and creation of binaries from source code. Using virtual environments would still be needed for building projects and its dependencies.
Question 2. What prevents us from uploading ghc to Hackage with a package name ghc-version having a binary name that depends on its version? e.g. one could cabal install ghc-version-7.6.2 and get a binary ghc-7.6.2 in ~/.cabal/bin
You don't need to do anything special. GHC already installs all of its executables with versioned names and links from the non-versioned name to the most recently installed version, e.g. a link from "ghc" to "ghc-7.6.1" or whatever you installed last. When you build from the repository, the version number is quite long and includes the date you built it.
I don't know for sure why GHC isn't on Hackage, but I presume it's because the build system is very complicated, and that cabal-izing it (and maintaining the cabalization) would be more work than it's worth.
There are several soluttions
Just use chroot
Use a package manager that handles multiple versions of the same library/software such as nix
There are scripts which have been written to handle this such as https://github.com/spl/multi-ghc
Use gnu stow as described in Brent Yorgey blog post.
Ben Millwood has a solution where he just uses the -w flag, read his comment at:https://plus.google.com/u/0/100165496075034135269/posts/VU9FupRvRbU
Related
I don't get the point about Stack.
I used to write my Haskell code in my favourite environment, ran or compiled using GHC(i), and if necessary, installed packages using Cabal. Now, that apparently is not the way to go any more, but I don't understand how to work with Stack. So far, I have only understood that I need to write stack exec ghci instead ghci to start a repl.
Apart from that, the docs always talk about 'projects' for which I have to write some yaml files. But I probably don't have any project -- I just want to launch a GHCi repl and experiment a bit with my ideas. At the moment, this fails with the unability to get the packages that I want to work with installed.
How is working with Stack meant? Is there any explanation of their use cases? Where do I find my use case in there?
Edit. My confusion comes from the fact that I want to work with some software (IHaskell) whose installation guide explains the installation via stack. Assuming I already have a GHCi installed whose package base I maintain e.g. using Cabal. How would I have to set up stack.yaml to make stack use my global GHCi for that project?
First, notice that stack will use its own package base independent from cabal. AFAIK they can't be shared... hence, if you run stack build it'll download packages (including the compiler) on its own package database.
Nevertheless stack allows to use a system compiler (but not other libraries). To do so, in the stack.yaml you must have the following two lines
resolver: lts-XX.XX -- keep reading below
system-ghc: True
The version of the stackage snapshot can be found in: https://www.stackage.org/. Each snapshot works with a different version of the compiler. Be sure to use a snapshot with the same compiler version you have in you system. If it happens your system ghc is greater than any lts, then you can set allow-newer: true in stack.yaml.
Now, if getting a different database from stack feels wrong to you, notice that you can build the project with cabal too, since stack at the end of the day spits out a cabal file. Probably, It wont work out of the box if you build with cabal. You can modify the cabal file to match exactly the version of the packages of the snapshot you are using
In summary:
You can use your system-wide ghc
you can not share libraries installed with cabal.
you can use cabal to build the project, probably modifying the ihaskell.cabal file to match versions of the stackage's snapshot.
I have a third-party library which depends on libgcc_s_sjlj-1.dll.
My own program is compiled under MSYS2 (mingw-w64) and it depends on libgcc_s_dw2-1.dll.
Please note that the third-party library is pure binaries (no source). Please also note that both libgcc_s_sjlj-1.dll and libgcc_s_dw2-1.dll are 32-bit, so I don't think it's an issue related to architecture.
The outcome is apparent, programs compiled based on libgcc_s_dw2-1.dll can't work with third-party libraries based on libgcc_s_sjlj-1.dll. What I get is a missing entrypoint __gxx_personality_sj0.
I can definitely try to adapt my toolchain to align with the third-party's libgcc_s_sjlj-1.dll, but I do not know how much effort I need to go about doing it. I find no such variant of libgcc dll under MSYS2 using this setjmp/longjmp version. I am even afraid that I need to eliminate the entire toolchain because all the binaries I had under MSYS2 sits atop this libgcc_s_dw2-1.dll module.
My goal is straightforward: I would like to find a solution so that my code will sit on top of libgcc_s_sjlj-1.dll instead of libgcc_s_dw2-1.dll. But I don't know if I am asking a stupid question simply because this is just not possible.
The terms dw2 and sjlj refer to two different types of exception handling that GCC can use on Windows. I don't know the details, but I wouldn't try to link binaries using the different types. Since MSYS2 does not provide an sjlj toolchain, you'll have to find one somewhere else. I would recommend downloading one from the "MingW-W64-builds" project, which you can find listed on this page:
https://mingw-w64.org/doku.php/download
You could use MSYS2 as a Bash shell but you can probably not link to any of its libraries in your program; you would need to recompile all libraries yourself (except for this closed source third-party one).
I need to install the same C++/Fortran library compiled with different compilers on the system with CMake. Is there a standard location where to install the different compiler-specific versions of the same library on the system? For example, assuming that lib.so and lib.a have already been installed using the system package manager under /usr/, is it good practice to install each of the additional compiler-specific versions in a different folder under let's say usr/local. Or is there a better way of doing this that you can advise?
It depends on how many compilers/libraries/versions you have. If you have just a few of them, I think that (almost) any choice on the location is right but I personally prefer /opt/ paths for manually installed code. But if you start having several combinations of them you easily get in trouble. Besides, I think that the question on the "best" location is related to the question on the "best" way to switch from the usage of one library to another one, possibly avoiding to manually set LD_LIBRARY_PATH, libraies to link or similar things.
I give some personal recommendations according to my experience for systems where you want to support many libraries/applications with many compilers/versions and also provide them for many users:
Do not use root user to install compiled software: just use an "installer account" and give read and execute permissions when needed to other users
Select a path for compiled software, e.g. /opt and define two subfolders /opt/build and /opt/install, the first one for your sources and where you compile them, the second as compilation target
Create some subfolders based on categories, e.g. /compilers, /libraries, /applications, ... from both /opt/build and /opt/install
Start preparing compilers under /compilers, e.g. /compilers/gnu/6.3 or /compilers/intel/2017. When possible compile them, e.g. from /opt/build/compilers/gnu/6.3 to /opt/install/compilers/gnu/6.3 or just put them into /install folder, e.g. /opt/install/compilers/intel/2017
Prepare the tree for libraries (or applications) adding subfolders which specify the version, the compiler and compiler version, e.g. compile from /opt/build/libraries/boost/1.64.0/gnu/6.3 and install to /opt/install/libraries/boost/1.64.0/gnu/6.3
At this stage, you have well organized things. But:
It is difficult to decide which library you want to use, you have to specify LD_LIBRARY_PATH or manually link the right one and the situation is worse when you deal also with applications
You are not considering dependencies between libraries: how can I force using g++ 6.3 when linking against boost/1.64.0/gnu/6.3?
To address these and many other issues, a good way of doing is using a tool which can help you, e.g. http://modules.sourceforge.net/ so that you can easily switch to one library to another one, force dependency, get help, and in general have something less error prone in the daily usage.
I have the Haskell Platform 2012.4 installed on Windows. I would like to try the new extensions in GHC 7.6.2. It looks like the GHC 7.6.2 x86_64 download does not include an installer and is just the binaries. What is the proper way to get the latest version installed and set as the default for building Haskell projects? Thanks.
If you download GHC itself, you just get GHC and a tiny handful of libraries. If you download the Haskell Platform, you get GHC plus a much bigger collection of libraries. However, the Haskell Platform is updated infrequently, so you'll get an older version of GHC.
If you're asking "how do I install the Haskell Platform and then make it work with a newer GHC?", then the answer is "you don't". Haskell libraries have to be compiled for the specific version of GHC you're using.
You basically have two options:
Use the Haskell Platform, together with the version of GHC that it supplies.
Use the latest GHC, and compile whatever libraries you want manually.
On Linux it's not too bad, but Haskell libraries that bind to external C code tend to be fiddly to build on Windows. (Stuff like OpenGL, zlib, etc.) Packages that are 100% vanilla Haskell code are drop-dead easy to compile on any system.
I haven't done this and I'm at work so I can't test it out, but looking at the GHC docs I would think you can use the --with-compiler=path flag to select which version of GHC to use?
See also this question, related to using cabal with multiple versions of ghc installed. I would guess that you probably want to use cabal-dev or something to sandbox this, otherwise your package database may become a mess.
EDIT: As far as a default, I think you can set that in a cabal configuration file. See the comments to the accepted answer in that question I linked.
The other answers here are great, and I wanted to add that the current best way to get the latest version of GHC installed is to look at haskell.org's installation instructions. I bounced between lots of different options before I landed there, and I think it's the best source of truth from what I can tell.
To summarize the current instructions: if you already have chocolately set up, "at an elevated command prompt, run choco install haskell-dev, followed by refreshenv."
I'd like to snapshot the global Hackage database into a frozen, smaller one for my company's deploys. How can one most easily copy out some segment of Hackage onto a private server?
Here's one script that does it in just about the simplest way possible: https://github.com/jamwt/mirror-hackage
You can also use the MirrorClient directly from the hackage2 repo: http://code.haskell.org/hackage-server/
This is not an answer two the question in the title but an answer to my interpretation of what the OP wish to achieve.
Depending of what you want for level of stability in your production circle you can approach the problem in several ways.
I have split the dependencies in two parts, things that I can use that are in the haskell platform (keep every platform used in production) and then only use a small number of packages outside that and don't let anyone (including yourself) add more packages into your dependency tree just because of laziness (as developer). These extra packages you use some kind of script for and collect from hackage (lock to version) by using cabal fetch. Keep them safe. Create a install script that uses your safe packages and if a new machine (developer) are added to your team, use that script.
yackage is great but it all comes down to how you ship your product. If you have older versions in production you need to have a yackage setup for every version and that could be quiet annoying after a couple of years.
You can download Hackage with Voker57's hackage-mirror.sh. You'll need 'curl' for it to run. If you're using a Debian based Linux distribution, you can install curl by typing apt-get install curl.
Though it's not a segment of Hackage, I've written a bash script, that downloads the whole Hackage, what can be further easily set up as a mirror using an HTTP server. Also, it downloads all required stuff like GHC compilers ready to be used with Stack.
Currently, a complete Hackage mirror occupies ~10GiB (~100000 packages of all versions) and Stack related stuff like GHC compilers ~21GiB (~200 files). Consequent runs of the script skip already downloaded stuff, so it downloads only new one. So it's a pretty convenient way to "live offline" and sync up to date when online.