# Debugging To profile a component of the current project, simply pass the `--profile` flag to `stack`. The `--profile` flag turns on the `--enable-library-profiling` and `--enable-executable-profiling` Cabal options _and_ passes the `+RTS -p` runtime options to any testsuites and benchmarks. For example the following command will build the `my-tests` testsuite with profiling options and create a `my-tests.prof` file in the current directory as a result of the test run. ~~~text stack test --profile my-tests ~~~ The `my-tests.prof` file now contains time and allocation info for the test run. To create a profiling report for an executable, e.g. `my-exe`, you can command: ~~~text stack exec --profile -- my-exe +RTS -p ~~~ For more fine-grained control of compilation options there are the `--library-profiling` and `--executable-profiling` flags which will turn on the `--enable-library-profiling` and `--enable-executable-profiling` Cabal options respectively. Custom GHC options can be passed in with `--ghc-options "more options here"`. To enable compilation with profiling options by default you can add the following snippet to your `stack.yaml` or `~/.stack/config.yaml`: ~~~yaml build: library-profiling: true executable-profiling: true ~~~ ## Further reading For more commands and uses, see the [official GHC chapter on profiling](https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.html), the [Haskell wiki](https://wiki.haskell.org/How_to_profile_a_Haskell_program), and the [chapter on profiling in Real World Haskell](http://book.realworldhaskell.org/read/profiling-and-optimization.html). ## Tracing To generate a backtrace in case of exceptions during a test or benchmarks run, use the `--trace` flag. Like `--profile` this compiles with profiling options, but adds the `+RTS -xc` runtime option. ## Debugging symbols Building with debugging symbols in the [DWARF information](https://ghc.haskell.org/trac/ghc/wiki/DWARF) is supported by Stack. This can be done by passing the flag `--ghc-options="-g"` and also to override the default behaviour of stripping executables of debugging symbols by passing either one of the following flags: `--no-strip`, `--no-library-stripping` or `--no-executable-stripping`. In Windows, GDB can be installed to debug an executable with `stack exec -- pacman -S gdb`. Windows' Visual Studio compiler's debugging format PDB is not supported at the moment. This might be possible by [separating](https://stackoverflow.com/questions/866721/how-to-generate-gcc-debug-symbol-outside-the-build-target) debugging symbols and [converting](https://github.com/rainers/cv2pdb) their format. Or as an option when [using the LLVM backend](http://blog.llvm.org/2017/08/llvm-on-windows-now-supports-pdb-debug.html).