#15425: GHC does not warn when two conflicting packages with same name are given via a dependent package and -package-db -------------------------------------+------------------------------------- Reporter: nh2 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Build System | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- So I'm compiling a Setup.hs of `mypackage`, directly with `ghc` and without use of `Cabal`. It has a custom build type and imports `Distribution.Extra.Doctest` from `cabal-doctest`. For compiling `mypackage`'s Setup.hs I give a `-package-db` that contains a custom `Cabal` package. But when I compiled `doctest`, I did not give that custom `Cabal` package. I compile with {{{ ghc -package-db=/tmp/nix-build-hsyslog-5.0.1.drv-0/setup-package.conf.d -package Cabal -j4 -threaded --make -o Setup -odir $TMPDIR -hidir $TMPDIR $i -fforce-recomp -keep-tmp-files -v5 }}} The given package db looks like this: {{{ % ls -lah /tmp/nix-build-hsyslog-5.0.1.drv-0/setup-package.conf.d total 56K drwxr-xr-x 2 niklas niklas 4.0K Jul 20 03:14 ./ drwxr-xr-x 12 niklas niklas 4.0K Jul 20 03:49 ../ -r--r--r-- 1 niklas niklas 11K Jul 20 02:30 Cabal-2.2.0.1-302vnEvwKgd3FEKLIV6HbI.conf -r--r--r-- 1 niklas niklas 2.3K Jul 20 02:30 cabal- doctest-1.0.6-E57gwmEN5fa2uY0bq8bb44.conf -rw-rw-r-- 1 niklas niklas 31K Jul 20 03:14 package.cache -rw-r--r-- 1 niklas niklas 0 Jul 20 02:30 package.cache.lock }}} Full [https://pastebin.com/raw/HpVLbe4A ghc-pkg dump -f /tmp/nix-build- hsyslog-5.0.1.drv-0/setup-package.conf.d output] This results in the linker flags: {{{ -L/nix/store/hfi080vzqqzfip6bd6x4cxc2jgj56xn3-ghc-8.4.3/lib/ghc-8.4.3/Cabal-2.2.0.1 -L/nix/store/6x9r3kqn8h961ilaw2nj474jrfyg28lp- Cabal-2.2.0.1/ghc-8.4.3/Cabal-2.2.0.1 ... -lHSCabal-2.2.0.1 -lHSCabal-2.2.0.1-302vnEvwKgd3FEKLIV6HbI }}} When this happens, GHC will always prefer the `Cabal` version from the global package db, and not the one I have given with `-package`. This results in my compiled `Setup` file to not use the Cabal version I desire. I would expect GHC to warn me when two Cabal versions are at play, or entirely refuse to compile, instead of picking the one that I have NOT explicitly specified. See full `-v5` ghc output here: https://pastebin.com/raw/jGbLPjxF -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15425 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler