building GHC overwrites the installed package database if GHC_PACKAGE_PATH is set
When building GHC, if
GHC_PACKAGE_PATH is set to a single path, then the build process will register packages in that path instead of in the build tree. Since
GHC_PACKAGE_PATH points to the host compiler's package database, the build system overwrites the host compiler's package database, rendering the host compiler unusable.
- Get a binary distribution of GHC 7.4.1 and a source distribution of GHC 7.4.2
- Configure the binary distribution to install in a temporary directory:
- Install the binary distribution
- Set up the environment to use only the installed compiler:
export PATH=$HOME/workspace1/bin:$PATH; export GHC_PACKAGE_PATH=$HOME/workspace1/lib/ghc-7.4.1/package.conf.d
- Configure the source distribution to install in a different directory:
- Build the source distribution:
Building will eventually run commands that modify the package database in
GHC_PACKAGE_PATH. One of these commands is
"inplace/bin/ghc-pkg" update --force rts/package.conf.inplace. I confirmed that the database is being modified by making
ghc-pkg print the name of the file it's about to update.