@ -793,6 +793,64 @@ It's important to realize, however, that most system libraries in Nix are built
as shared libraries only, i.e. there is just no static library available that
Cabal could link!
### Building GHC with integer-simple
By default GHC implements the Integer type using the
[GNU Multiple Precision Arithmetic (GMP) library ](https://gmplib.org/ ).
The implementation can be found in the
[integer-gmp ](http://hackage.haskell.org/package/integer-gmp ) package.
A potential problem with this is that GMP is licensed under the
[ GNU Lesser General Public License (LGPL) ](http://www.gnu.org/copyleft/lesser.html ),
a kind of "copyleft" license. According to the terms of the LGPL, paragraph 5,
you may distribute a program that is designed to be compiled and dynamically
linked with the library under the terms of your choice (i.e., commercially) but
if your program incorporates portions of the library, if it is linked
statically, then your program is a "derivative"--a "work based on the
library"--and according to paragraph 2, section c, you "must cause the whole of
the work to be licensed" under the terms of the LGPL (including for free).
The LGPL licensing for GMP is a problem for the overall licensing of binary
programs compiled with GHC because most distributions (and builds) of GHC use
static libraries. (Dynamic libraries are currently distributed only for OS X.)
The LGPL licensing situation may be worse: even though
[The Glasgow Haskell Compiler License](https://www.haskell.org/ghc/license)
is essentially a "free software" license (BSD3), according to
paragraph 2 of the LGPL, GHC must be distributed under the terms of the LGPL!
To work around these problems GHC can be build with a slower but LGPL-free
alternative implemention for Integer called
[integer-simple ](http://hackage.haskell.org/package/integer-simple ).
To get a GHC compiler build with `integer-simple` instead of `integer-gmp` use
the attribute: `pkgs.haskell.compiler.integer-simple."${ghcVersion}"` .
For example:
$ nix-build -E '(import < nixpkgs > {}).pkgs.haskell.compiler.integer-simple.ghc802'
...
$ result/bin/ghc-pkg list | grep integer
integer-simple-0.1.1.1
The following command displays the complete list of GHC compilers build with `integer-simple` :
$ nix-env -f "< nixpkgs > " -qaP -A haskell.compiler.integer-simple
haskell.compiler.integer-simple.ghc7102 ghc-7.10.2
haskell.compiler.integer-simple.ghc7103 ghc-7.10.3
haskell.compiler.integer-simple.ghc722 ghc-7.2.2
haskell.compiler.integer-simple.ghc742 ghc-7.4.2
haskell.compiler.integer-simple.ghc763 ghc-7.6.3
haskell.compiler.integer-simple.ghc783 ghc-7.8.3
haskell.compiler.integer-simple.ghc784 ghc-7.8.4
haskell.compiler.integer-simple.ghc801 ghc-8.0.1
haskell.compiler.integer-simple.ghc802 ghc-8.0.2
haskell.compiler.integer-simple.ghcHEAD ghc-8.1.20170106
To get a package set supporting `integer-simple` use the attribute:
`pkgs.haskell.packages.integer-simple."${ghcVersion}"` . For example
use the following to get the `scientific` package build with `integer-simple` :
$ nix-build -A pkgs.haskell.packages.integer-simple.ghc802.scientific
## Other resources