I always keep:
executable-profiling: True
library-profiling: True
in my ~/.cabal/config. Profiling is useful, and its a pain when you cannot use it.
But ghc-vis doesn't work with profiling. That's a bummer. Should I recompile the universe every time I want to use ghc-vis? Should I use cabal-dev and move things back and forth?
No!
There's a better way(tm). That is config-select
config-select is a program which is generally usefull for swapping out config files.
It can be installed with the command:
cabal install config-select
It was origionally developed as an X11 display manager to swap out .xinitrc files.
It provides you with a nice menu to select the configuration profile you want. Or you can pass a profile's name via the command line to load it instantly.
The fundimental files directories of config-select are as follows:
A profiles directory:
~/.xinitrc.d/
A profile directory:
~/.xinitrc.d/xmonad/
A config file:
~/.xinitrc.d/xomand/.xinitrc
Or two:
~/.xinitrc.d/xmonad/.xmodmap
Symlinks to the config files.
lrwxrwxrwx 1 timothy timothy 40 6. úno 21.49 .xinitrc -> .xinitrc.d/xmonad/.xinitrc
lrwxrwxrwx 1 timothy timothy 40 6. úno 21.49 .xmodmap -> .xinitrc.d/xmonad/.xmodmap
config-select can be now run by the command:
config-select $HOME $HOME/.xinitrc.d/
I have a script in my ~/bin directory named csdm:
#!/bin/bash
config-select $HOME $HOME/configs/xinitrc.d/ $1
exec startx
and I can either run
$ csdm
to see a menu and choose between xfce and xmonad or I can run
$ csdm xmonad to launch xmonad directly.
Dealing with the ghc problem is quite similar. Here is my ~/bin/csghc:
#!/bin/bash
config-select $HOME $HOME/configs/ghc.d/ $1
I then have a ghc.d directory with two subdirectories:
[timothy@timothy ghc.d]$ ls -la noprofiling-default/
celkem 4
drwxr-xr-x 1 timothy timothy 30 6. úno 22.51 .
drwxr-xr-x 1 timothy timothy 56 6. úno 22.52 ..
drwxr-xr-x 1 timothy timothy 68 6. úno 22.27 .cabal
drwxr-xr-x 1 timothy timothy 60 6. úno 22.24 .ghc
-rw-r--r-- 1 timothy timothy 114 6. úno 22.27 .ghci
[timothy@timothy ghc.d]$ ls -la profiling/
celkem 8
drwxr-xr-x 1 timothy timothy 56 6. úno 22.57 .
drwxr-xr-x 1 timothy timothy 56 6. úno 22.52 ..
drwxr-xr-x 1 timothy timothy 68 6. úno 22.15 .cabal
-rw-r--r-- 1 timothy timothy 2159 9. zář 19.42 .cabal-config
drwxr-xr-x 1 timothy timothy 96 11. říj 11.39 .ghc
-rw-r--r-- 1 timothy timothy 1 6. úno 22.57 .ghci
There are several complications: The first is that the files in the two directories should be the same. config-select swaps out only files that it finds within the selected profile.
That means, that even though with profiling turned on, I have no need for a ~/.ghci file, it is blank:
`[timothy@timothy ghc.d]$ cat profiling/.ghci
[timothy@timothy ghc.d]$ cat noprofiling-default/.ghci :script /home/timothy/.cabal/share/ghc-heap-view-0.4.2.0/ghci :script /home/timothy/.cabal/share/ghc-vis-0.6/ghci`
I still need a place holder there, so that the ~/.ghci file installed when noprofiling-default is activated will get replaced by something reasonable when I'm using the profile with profiling enabled.
The seccond complication is more benign.
One must have ~/.cabal/bin in ones $PATH.
But if we are to swap out our ~/.cabal directory this can lead to otherwise usefull and installed exicutables dissapearing from the path.
My solution is to have a ~/.bashrc that looks like this:
PATH=$PATH:$HOME/.cabal/bin:$HOME/configs/ghc.d/profiling/.cabal/bin:$HOME/bin/
This says that bash should first look for programs installed in ~/.cabal/bin and when it doesn't find them, it can then continue searching in ~/configs/ghc.d/profiling/.cabal/.
I hope you enjoyed this tutorial, and I look forward to any feedback and sugestions.
I have been careful to make config-select not delete everything on your computer. However, please note that it is still in the testing phase. Use at your own risk.
Tim