Haskell .gitignore template

The compiler emits an object file and an interface file for every module. *.o is the object, *.hi is the interface that records the module's exported types and signatures so dependent modules can be compiled without reparsing the source. The *.dyn_o and *.dyn_hi variants are the dynamically linked equivalents, and *.hie holds the extended syntax information that editor tooling reads. All five are derived and version specific.

dist and dist-* are the output directories for the standard build tool, with the suffixed variants coming from the newer per compiler layout. .stack-work is the equivalent for the other common build tool, holding compiled dependencies, generated cabal files and a full package database. cabal-dev and .cabal-sandbox are earlier isolation mechanisms that predate both.

cabal.project.local is where you record settings for your own checkout: which compiler to use, local package overrides, flags you enabled while debugging. It is the file that lets you deviate from the shared project definition, which is exactly why it should not be shared. The tilde suffixed variant is a backup of it.

The profiling rules cover *.prof, *.hp and *.eventlog. These are produced by running an executable built with profiling enabled: a cost centre report, a heap profile and an event log for the threaded runtime. They describe one run on one machine, and they get large quickly. .hpc holds coverage data from the same family of tools.

.ghc.environment.* files are written when you build outside a project context, recording which packages are visible to the compiler on this machine. *.chi and *.chs.h come from the C interface preprocessor, and *.aux is a leftover from the documentation toolchain.