Why many .tix files are generated in Haskell Program Coverage
I am using Haskell Program Coverage (HPC) to collect coverage information for Pandoc (https://github.com/jgm/pandoc). However, after adding the -fhpc option to GHC and running the program, two .tix files are generated. One is test-pandoc.tix in the main directory and the other is pandoc.tix under the "test" directory (test/pandoc.tix). These two files have different contents and I just cannot see the meaning of them from their names. Moreover, I tried to execute "hpc show xxx.tix" for them and test/pandoc.tix gives "hpc: hash in tix file for module Main does not match hash in ./.hpc/Main.mix".
So, I wonder the specific generation rules of HPC tix files (possibly including the number and location) and how I can get the correct coverage information.