This patch configures all Cabal builds with '--enable-split-objs' unless the
Nix expression explicitly sets "enableSplitObjs = false". The Cabal manual [1]
describes this option as follows:
| The GHC -split-objs reduces the final size of the executables that use the
| library by allowing them to link with only the bits that they use rather
| than the entire library. The downside is that building the library takes
| longer and uses considerably more memory.
One immediate benefit of this change is that the 'darcs' closure defined in the
top-level no longer refers to GHC. The same is probably true with other
executable packages.
[1] http://www.haskell.org/cabal/users-guide/installing-packages.html#setup-configure
The use case is to do a deep replacement of a dependency without rebuilding the entire tree.
For example, suppose a security hole is found in glibc and a patch released. Ideally, you'd
just rebuild everything, but that takes time, space, and CPU that you might not have, so in
the mean time you could build a safe version of, say, firefox with:
firefox-safe = replace-dependency { drv = firefox; old-dependency = glibc; new-dependency = patched-glibc; };
Building firefox-safe will rebuild glibc, but only do a simple copy/string replacement on all other dependencies
of firefox. On my system (MBP 13" mid-2012), after a new glibc had been build building firefox took around 11 seconds.
See the comments in the file for more details.
Conflicts:
pkgs/development/compilers/gcc/4.6/default.nix
pkgs/development/compilers/gcc/4.7/default.nix
The 4.7 had some weird parameters added in crossAttrs; I've removed
them, but I don't understand where they come from.
This is for consistency with terminology in stdenv (and the terms
"hostDrv" and "buildDrv" are not very intuitive, even if they're
consistent with GNU terminology).
Added support code for comfortable writing of upstream data update
expressions that do not require change of layout of the updated
expressions (although they make assumptions about single assignment per
line). Also added a default for choosing file to update (it is supposed
to be default.nix in the same directory) and a one-liner for typical
sourceforge redirects (and sourceforge mirror:// handling).
