Adding debug symbols to package from nixpkgs

jacg · March 23, 2021, 1:07pm

I’m writing some C++ code that uses a framework (Geant4) which I have installed from nixpkgs. Debug symbols seem to be missing. How would I go about adding them?

I would expect debug symbols to be needed quite frequently, and therefore I would hope that there is a simple switch for enabling them, but if there is such a thing, I haven’t managed to find it.

In my specific case, Geant4 is compiled with cmake, so I guess that I could

add an overlay which adds -DCMAKE_BUILD_TYPE=Debug to cmakeFlags
wait 2 hours for the whole thing to compile

but I hope that there’s a better way. Is there?

abathur · March 23, 2021, 3:00pm

Edit: See danieldk’s response after this one first

It looks like you can set the build type with cmakeBuildType = "Debug";:

github.com

NixOS/nixpkgs/blob/f5e8bdd07d1afaabf6b37afc5497b1e498b8046f/pkgs/development/tools/build-managers/cmake/setup-hook.sh#L107


      
          cmakeFlags="-DCMAKE_INSTALL_LIBEXECDIR=${!outputLib}/libexec $cmakeFlags"
          cmakeFlags="-DCMAKE_INSTALL_LOCALEDIR=${!outputLib}/share/locale $cmakeFlags"
          
          
# Don’t build tests when doCheck = false
          if [ -z "${doCheck-}" ]; then
              cmakeFlags="-DBUILD_TESTING=OFF $cmakeFlags"
          fi
          
          
# Avoid cmake resetting the rpath of binaries, on make install
          # And build always Release, to ensure optimisation flags
          cmakeFlags="-DCMAKE_BUILD_TYPE=${cmakeBuildType:-Release} -DCMAKE_SKIP_BUILD_RPATH=ON $cmakeFlags"
          
          
# Disable user package registry to avoid potential side effects
          # and unecessary attempts to access non-existent home folder
          # https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#disabling-the-package-registry
          cmakeFlags="-DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON $cmakeFlags"
          cmakeFlags="-DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF $cmakeFlags"
          cmakeFlags="-DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF $cmakeFlags"
          
          
if [ "${buildPhase-}" = ninjaBuildPhase ]; then
              cmakeFlags="-GNinja $cmakeFlags"

I found a small number of examples in Nixpkgs, including:

github.com

NixOS/nixpkgs/blob/d600f006643e074c2ef1d72e462e218b647a096c/pkgs/applications/science/misc/simgrid/default.nix#L46


      
          
          
#buildInputs = optional luaSupport lua5;
          
          
# Make it so that libsimgrid.so will be found when running programs from
          # the build dir.
          preConfigure = ''
            export LD_LIBRARY_PATH="$PWD/build/lib"
          '';
          
          
# Release mode is not supported in SimGrid
          cmakeBuildType = "Debug";
          
          
# Disable/Enable functionality
          # Note: those packages are not packaged in Nixpkgs yet so some options
          # are disabled:
          # - papi:   for enable_smpi_papi
          # - ns3:    for enable_ns3
          # - lua53:  for enable_lua
          #
          # For more information see:
          # https://simgrid.org/doc/3.22/Installing_SimGrid.html#simgrid-compilation-options)

(but I doubt you’ll be spared from waiting for it to compile? Unless maybe someone’s intentionally caching debug builds?)

danieldk · March 23, 2021, 3:21pm

Unless you want to run a debug build of the library, you probably just want debug information, which can be enabled using separateDebugInfo, which is described in the manual:

Unfortunately, this is only enabled for a small number of derivations in nixpkgs (e.g. glibc), so for all other packages this means that you have to rebuild them. IIRC the main concern for enabling separate debug info for all packages was the amount of storage required in the binary cache.

There is also a nice FUSE filesystem dwarffs, which will automatically download debug info for the packages for which it is available when using gdb: