diff --git a/.github/workflows/backend-template.yml b/.github/workflows/backend-template.yml
index 7f0d6b6b0..6f08cf0b9 100644
--- a/.github/workflows/backend-template.yml
+++ b/.github/workflows/backend-template.yml
@@ -25,6 +25,10 @@ on:
         description: "Name of the branch of the backend repository"
         required: true
         type: string
+      container_name:
+        description: "Name of the container used to build on"
+        required: true
+        type: string
       vmd_plugins_repo:
         description: "Name of the VMD plugins repository"
         required: false
@@ -71,7 +75,7 @@ jobs:
         with:
           path: |
             ~/.ccache
-            ~/ccache_CentOS7-devel
+            ~/ccache_${{ inputs.container_name }}
           key: ${{ runner.os }}-build-${{ inputs.backend_name }}-${{ github.sha }}
           restore-keys: |
             ${{ runner.os }}-build-${{ inputs.backend_name }}-
@@ -82,7 +86,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ~/.apptainer
-          key: Linux-x86_64-containers-build-2022-10-11
+          key: Linux-x86_64-containers-build-2023-07-20
 
       - name: Checkout OpenMM (for Lepton library)
         uses: actions/checkout@v3
@@ -122,29 +126,30 @@ jobs:
           wget https://github.com/apptainer/apptainer/releases/download/v1.0.3/apptainer_1.0.3_amd64.deb
           sudo apt-get -y install ./apptainer_1.0.3_amd64.deb
 
-      - name: Get container image of backends' dependencies
+      - name: Get container images for build dependencies
         shell: bash
         working-directory: devel-tools
         run: |
-          # Pull CentOS 7 container used to build backends
+          # Pull all containers used to build backends
           # (contains build tools, OpenMPI, FFTW, Tcl/Tk and Charm++)
           apptainer remote status SylabsCloud || apptainer remote add --no-login SylabsCloud cloud.sylabs.io
           apptainer remote use SylabsCloud
           apptainer pull CentOS7-devel.sif library://giacomofiorin/default/colvars_development:centos7
+          apptainer pull CentOS9-devel.sif library://giacomofiorin/default/colvars_development:centos9
 
       - name : Get spiff
         shell: bash
         working-directory: devel-tools
-        run: sudo cp -f $(apptainer exec CentOS7-devel.sif ./get_spiff) /usr/local/bin
+        run: sudo cp -f $(apptainer exec ${{ inputs.container_name }}.sif ./get_spiff) /usr/local/bin
 
       - name: Update and build ${{ inputs.backend_name }}
         shell: bash
         env:
           OPENMM_SOURCE: ${{ github.workspace }}/openmm-source
         run: |
-          apptainer exec devel-tools/CentOS7-devel.sif ./update-colvars-code.sh -f ${{ inputs.backend_name }}-source
-          CCACHE_DIR=~/ccache_CentOS7-devel \
-          apptainer exec devel-tools/CentOS7-devel.sif \
+          apptainer exec devel-tools/${{ inputs.container_name }}.sif ./update-colvars-code.sh -f ${{ inputs.backend_name }}-source
+          CCACHE_DIR=~/ccache_${{ inputs.container_name }} \
+          apptainer exec devel-tools/${{ inputs.container_name }}.sif \
           bash ${{ inputs.path_compile_script }} ${{ inputs.backend_name }}-source
 
 
@@ -157,7 +162,7 @@ jobs:
         shell: bash
         working-directory: ${{ inputs.test_lib_directory }}
         run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
+          apptainer exec ${{github.workspace}}/devel-tools/${{ inputs.container_name }}.sif \
           ./run_tests.sh ${{github.workspace}}/${{ inputs.backend_name }}-source/${{ inputs.rpath_exe }} 0??_*
 
       - name: Save failed library test artifact
@@ -172,7 +177,7 @@ jobs:
         shell: bash
         working-directory: ${{ inputs.test_interface_directory }}
         run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
+          apptainer exec ${{github.workspace}}/devel-tools/${{ inputs.container_name }}.sif \
           ./run_tests.sh ${{github.workspace}}/${{ inputs.backend_name }}-source/${{ inputs.rpath_exe }}
 
       - name: Save failed interface test artifact
diff --git a/.github/workflows/test-backends.yml b/.github/workflows/test-backends.yml
index 62e10e7b4..266972893 100644
--- a/.github/workflows/test-backends.yml
+++ b/.github/workflows/test-backends.yml
@@ -26,6 +26,7 @@ jobs:
       backend_name: LAMMPS
       backend_repo: lammps/lammps
       backend_repo_ref: develop
+      container_name: CentOS7-devel
       path_compile_script: devel-tools/compile-lammps.sh
       test_lib_directory: lammps/tests/library
       test_interface_directory: lammps/tests/interface
@@ -43,6 +44,7 @@ jobs:
       backend_name: NAMD
       backend_repo: Colvars/namd
       backend_repo_ref: master
+      container_name: CentOS7-devel
       path_compile_script: devel-tools/compile-namd.sh
       test_lib_directory: namd/tests/library
       test_interface_directory: namd/tests/interface
@@ -68,6 +70,7 @@ jobs:
       # Interface tests disabled until map variables are merged into NAMD3
       # test_interface_directory: namd/tests/interface
       rpath_exe: Linux-x86_64-g++.multicore/namd3
+      container_name: CentOS7-devel
     secrets:
       # Choice of license by UIUC prevents sharing the code, hence the secret
       private_key: ${{ secrets.PULL_NAMD_KEY }}
@@ -84,6 +87,7 @@ jobs:
       backend_name: VMD
       backend_repo: Colvars/vmd
       backend_repo_ref: master
+      container_name: CentOS7-devel
       # Special variable for VMD test case since it's the only one
       # which needs to checkout 2 repos
       vmd_plugins_repo: Colvars/vmd-plugins
@@ -103,6 +107,7 @@ jobs:
       backend_name: GROMACS-2020
       backend_repo: gromacs/gromacs
       backend_repo_ref: release-2020
+      container_name: CentOS7-devel
       path_compile_script: devel-tools/compile-gromacs.sh
       test_lib_directory: gromacs/tests/library
       # Gromacs need to be compiled in double precision to pass the tests
@@ -116,6 +121,7 @@ jobs:
       backend_name: GROMACS-2021
       backend_repo: gromacs/gromacs
       backend_repo_ref: release-2021
+      container_name: CentOS9-devel
       path_compile_script: devel-tools/compile-gromacs.sh
       test_lib_directory: gromacs/tests/library
       rpath_exe: install/bin/gmx_d
@@ -128,6 +134,7 @@ jobs:
       backend_name: GROMACS-2022
       backend_repo: gromacs/gromacs
       backend_repo_ref: release-2022
+      container_name: CentOS9-devel
       path_compile_script: devel-tools/compile-gromacs.sh
       test_lib_directory: gromacs/tests/library
       rpath_exe: install/bin/gmx_d
diff --git a/.github/workflows/test-library.yml b/.github/workflows/test-library.yml
index 23fd0e834..3b81d5050 100644
--- a/.github/workflows/test-library.yml
+++ b/.github/workflows/test-library.yml
@@ -33,7 +33,7 @@ jobs:
 
       - name: Install build dependencies for library
         run: |
-          sudo apt-get -y install ccache tcl8.6-dev
+          sudo apt -y install ccache tcl8.6-dev clang
 
       - name: Test build recipes
         run: bash devel-tools/check_build_recipes
@@ -48,7 +48,7 @@ jobs:
               exit 1
           fi
 
-      - name: Build and test library with CMake
+      - name: Build and test library (GCC)
         env:
           CCACHE: ccache
         run: cmake -P devel-tools/build_test_library.cmake
@@ -63,6 +63,14 @@ jobs:
               exit 1
           fi
 
+      - name: Build and test library (Clang)
+        env:
+          CMAKE_BUILD_DIR: build-clang
+          CCACHE: ccache
+          CXX: clang++
+          CC: clang
+        run: cmake -P devel-tools/build_test_library.cmake
+
       - name: Build library with debug flags enabled
         env:
           CCACHE: ccache
@@ -88,7 +96,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ~/.apptainer
-          key: Linux-x86_64-containers-build-doc-2022-09-03
+          key: Linux-x86_64-containers-build-doc-2023-07-19
 
       - name: Install Apptainer
         shell: bash
@@ -102,7 +110,7 @@ jobs:
         run: |
           apptainer remote status SylabsCloud || apptainer remote add --no-login SylabsCloud cloud.sylabs.io
           apptainer remote use SylabsCloud
-          apptainer pull Fedora35-texlive.sif library://giacomofiorin/default/colvars_development:fedora35_texlive
+          apptainer pull texlive.sif library://giacomofiorin/default/colvars_development:texlive
 
       - name: Checkout website repository
         uses: actions/checkout@v3
@@ -115,7 +123,7 @@ jobs:
         env:
           COLVARSDIR: ${{ github.workspace }}
           FORCE: 1  # Ignore error if branch isn't master
-        run: apptainer exec ${COLVARSDIR}/devel-tools/Fedora35-texlive.sif make
+        run: apptainer exec ${COLVARSDIR}/devel-tools/texlive.sif make
 
 
   codeql:
@@ -174,7 +182,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ~/.apptainer
-          key: Linux-x86_64-containers-build-2022-10-11
+          key: Linux-x86_64-containers-build-2023-07-20
 
       - name: Get small downloadable packages
         uses: actions/checkout@v3
@@ -196,8 +204,9 @@ jobs:
           apptainer remote status SylabsCloud || apptainer remote add --no-login SylabsCloud cloud.sylabs.io
           apptainer remote use SylabsCloud
           apptainer pull CentOS7-devel.sif library://giacomofiorin/default/colvars_development:centos7
+          apptainer pull CentOS9-devel.sif library://giacomofiorin/default/colvars_development:centos9
 
-      - name: GCC 4.8, C++11
+      - name: GCC 4.8, C++11 (CentOS 7)
         env:
           CXX_STANDARD: 11
           CXX: g++
@@ -207,29 +216,7 @@ jobs:
           apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 8, C++17
-        env:
-          CXX_STANDARD: 17
-          CXX: g++
-          CXX_VERSION: 8
-          CC: gcc
-        run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
-          scl enable devtoolset-${CXX_VERSION} -- \
-          cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
-
-      - name: GCC 11, C++20
-        env:
-          CXX_STANDARD: 20
-          CXX: g++
-          CXX_VERSION: 11
-          CC: gcc
-        run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
-          scl enable devtoolset-${CXX_VERSION} -- \
-          cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
-
-      - name: Clang 3.4, C++11
+      - name: Clang 3.4, C++11 (CentOS 7)
         env:
           CXX_STANDARD: 11
           CXX: clang++
@@ -239,7 +226,7 @@ jobs:
           apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: Clang 7, C++17
+      - name: Clang 7, C++17 (CentOS 7)
         env:
           CXX_STANDARD: 17
           CXX: clang++
@@ -250,29 +237,29 @@ jobs:
           scl enable llvm-toolset-${CXX_VERSION} -- \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 11, C++17
+      - name: GCC 8, C++14 (CentOS 7)
         env:
-          CXX_STANDARD: 17
+          CXX_STANDARD: 14
           CXX: g++
-          CXX_VERSION: 11
+          CXX_VERSION: 8
           CC: gcc
         run: |
           apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
           scl enable devtoolset-${CXX_VERSION} -- \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 10, C++17
+      - name: GCC 8, C++17 (CentOS 7)
         env:
           CXX_STANDARD: 17
           CXX: g++
-          CXX_VERSION: 10
+          CXX_VERSION: 8
           CC: gcc
         run: |
           apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
           scl enable devtoolset-${CXX_VERSION} -- \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 9, C++14
+      - name: GCC 9, C++14 (CentOS 7)
         env:
           CXX_STANDARD: 14
           CXX: g++
@@ -283,49 +270,109 @@ jobs:
           scl enable devtoolset-${CXX_VERSION} -- \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 8, C++14
+      - name: GCC 10, C++17 (CentOS 7)
         env:
-          CXX_STANDARD: 14
+          CXX_STANDARD: 17
           CXX: g++
-          CXX_VERSION: 8
+          CXX_VERSION: 10
           CC: gcc
         run: |
           apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
           scl enable devtoolset-${CXX_VERSION} -- \
           cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 8, C++11
+
+      - name: GCC 11, C++11 (CentOS 9)
         env:
           CXX_STANDARD: 11
           CXX: g++
-          CXX_VERSION: 8
+          CXX_VERSION: 11
           CC: gcc
         run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
-          scl enable devtoolset-${CXX_VERSION} -- \
-          cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 7, C++14
+      - name: GCC 11, C++14 (CentOS 9)
         env:
           CXX_STANDARD: 14
           CXX: g++
-          CXX_VERSION: 7
+          CXX_VERSION: 11
           CC: gcc
         run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
-          scl enable devtoolset-${CXX_VERSION} -- \
-          cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: GCC 11, C++17 (CentOS 9)
+        env:
+          CXX_STANDARD: 17
+          CXX: g++
+          CXX_VERSION: 11
+          CC: gcc
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
-      - name: GCC 7, C++11
+      - name: GCC 11, C++20 (CentOS 9)
+        env:
+          CXX_STANDARD: 20
+          CXX: g++
+          CXX_VERSION: 11
+          CC: gcc
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: GCC 12, C++11 (CentOS 9)
         env:
           CXX_STANDARD: 11
           CXX: g++
-          CXX_VERSION: 7
+          CXX_VERSION: 12
           CC: gcc
         run: |
-          apptainer exec ${{github.workspace}}/devel-tools/CentOS7-devel.sif \
-          scl enable devtoolset-${CXX_VERSION} -- \
-          cmake3 -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          scl enable gcc-toolset-12 -- \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: GCC 12, C++20 (CentOS 9)
+        env:
+          CXX_STANDARD: 20
+          CXX: g++
+          CXX_VERSION: 12
+          CC: gcc
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          scl enable gcc-toolset-12 -- \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: Clang 16, C++11 (CentOS 9)
+        env:
+          CXX_STANDARD: 11
+          CXX: clang++
+          CXX_VERSION: 16
+          CC: clang
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: Clang 16, C++17 (CentOS 9)
+        env:
+          CXX_STANDARD: 17
+          CXX: clang++
+          CXX_VERSION: 16
+          CC: clang
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
+
+      - name: Clang 16, C++20 (CentOS 9)
+        env:
+          CXX_STANDARD: 20
+          CXX: clang++
+          CXX_VERSION: 16
+          CC: clang
+        run: |
+          apptainer exec ${{github.workspace}}/devel-tools/CentOS9-devel.sif \
+          cmake -D CMAKE_CXX_STANDARD=${CXX_STANDARD} -P devel-tools/build_test_library.cmake
 
 
   build-linux-x86_64-sun:
@@ -340,7 +387,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ~/.apptainer
-          key: Linux-x86_64-containers-build-2022-10-11
+          key: Linux-x86_64-containers-build-2023-07-20
 
       - name: Checkout Sun compiler (Oracle Developer Studio)
         uses: actions/checkout@v3
@@ -370,6 +417,7 @@ jobs:
           apptainer remote status SylabsCloud || apptainer remote add --no-login SylabsCloud cloud.sylabs.io
           apptainer remote use SylabsCloud
           apptainer pull CentOS7-devel.sif library://giacomofiorin/default/colvars_development:centos7
+          apptainer pull CentOS9-devel.sif library://giacomofiorin/default/colvars_development:centos9
 
       - name: Build library with Sun compiler (Oracle Developer Studio)
         shell: bash
diff --git a/colvartools/plot_colvars_traj.py b/colvartools/plot_colvars_traj.py
index b396b70e0..00f3e42ab 100644
--- a/colvartools/plot_colvars_traj.py
+++ b/colvartools/plot_colvars_traj.py
@@ -3,7 +3,7 @@
 # Invoke this script with --help for documentation.
 
 # Download link: https://github.com/Colvars/colvars/blob/master/colvartools/plot_colvars_traj.py?raw=true
-# This version was modified on: 2022-09-12
+# This version was modified on: 2023-07-13
 # Contact: giacomo.fiorin@gmail.com
 
 from __future__ import print_function
@@ -143,6 +143,8 @@ def _parse_comment_line(self, line):
         self._keys = new_keys
         # Find the boundaries of each column
         for i in range(1, len(self._keys)):
+            if (self._keys[i] not in self._colvars):
+                self._colvars[self._keys[i]] = Colvar_traj(self._keys[i])
             if i == 1:
                 pos = line.find(' '+self._keys[i]+' ')
             else:
@@ -152,7 +154,6 @@ def _parse_comment_line(self, line):
             self._end[self._keys[i-1]] = pos
         self._end[self._keys[-1]] = -1
 
-
     def _parse_line(self, line, dict_buffer):
         """
         Read in a data line from a colvars.traj file
@@ -226,10 +227,8 @@ def read_files(self, filenames, list_variables=False,
                 last_step = step
 
             for key in dict_buffer:
-                if (key not in self._colvars):
-                    self._colvars[key] = Colvar_traj(key)
-                    self._colvars[key]._set_num_dimensions(dict_buffer[key]['dimension'])
                 cv = self._colvars[key]
+                cv._set_num_dimensions(dict_buffer[key]['dimension'])
                 cv._step = np.concatenate((cv.steps, dict_buffer[key]['cv_step']), axis=0)
                 cv._colvar = np.concatenate((cv.values, dict_buffer[key]['cv_values']), axis=0)
             f.close()
diff --git a/devel-tools/compile-namd.sh b/devel-tools/compile-namd.sh
index d1dc3ae28..6f206b64a 100755
--- a/devel-tools/compile-namd.sh
+++ b/devel-tools/compile-namd.sh
@@ -72,7 +72,14 @@ EOF
 
     cmd+=(--tcl-prefix ${TCL_HOME:-/usr})
     cmd+=(--with-fftw3 --fftw-prefix ${FFTW_HOME:-/usr})
-    cmd+=(--with-python)
+
+    local python_version=$(python3 --version 2> /dev/null | cut -d' ' -f 2)
+    python_version=${python_version%.*}
+    if [ "x${python_version}" == "x3.6" ] || [ "x${python_version}" == "x3.7" ] || \
+        [ "x${python_version}" == "x3.8" ] ; then
+        # Currently does not build with >= 3.9 API
+        cmd+=(--with-python)
+    fi
 
     eval ${cmd[@]}
 
diff --git a/devel-tools/containers/CentOS7-devel.def b/devel-tools/containers/CentOS7-devel.def
new file mode 100644
index 000000000..16aaf68bc
--- /dev/null
+++ b/devel-tools/containers/CentOS7-devel.def
@@ -0,0 +1,49 @@
+BootStrap: library
+From: centos:7
+
+
+%help
+    Development environment for CentOS 7
+
+
+%post
+    yum -y update
+    yum -y install epel-release centos-release-scl
+    yum -y install \
+        redhat-lsb-core "@Development Tools" \
+        ncurses which bc man-db vim emacs screen tmux \
+        gcc gcc-c++ gcc-gfortran glibc-static libstdc++-static clang cppcheck \
+        autoconf automake  cvs git git-cvs cvsps subversion mercurial \
+        rh-git227 devtoolset-{7..11} llvm-toolset-7 cmake3 ccache ninja \
+        doxygen \
+        openmpi-devel fftw-devel tcl-devel \
+        python-{devel,virtualenv} numpy scipy tkinter \
+        python3-{devel,tkinter} python36-{virtualenv,numpy,scipy} \
+        rh-python38-python-{devel,tkinter,numpy,scipy} \
+        boost169-devel \
+        ncurses-devel \
+        rlwrap \
+        tk-devel fltk-devel \
+        sqlite-devel netcdf-devel expat-devel hdf5-devel tng-devel \
+        mesa-dri-drivers mesa-libGL-devel libglvnd-devel \
+        libXi-devel libXinerama-devel libpng-devel \
+        xfce4-terminal \
+        texlive-latex texlive-epstopdf texlive-pdftex latex2html \
+        texlive-graphics texlive-metafont \
+        texlive-collection-latexrecommended texlive-collection-fontsrecommended
+
+    # Build Charm++
+    umask 022
+    git clone --single-branch --depth=1 -b v7.0.0 https://github.com/UIUC-PPL/charm.git /opt/charm && \
+        cd /opt/charm && \
+        ./build charm++ mpi-linux-x86_64 -j\$(nproc) --with-production && \
+        ./build charm++ multicore-linux-x86_64 -j\$(nproc) --with-production && \
+        ./build charm++ netlrts-linux-x86_64 -j\$(nproc) --with-production
+
+    # Load Git 2.27
+    cat > /etc/profile.d/git.sh <<EOF
+if [ \$(id -u) != 0 ] && [ -d /opt/rh/rh-git227 ] ; then
+    source /opt/rh/rh-git227/enable
+fi
+EOF
+
diff --git a/devel-tools/containers/CentOS9-devel.def b/devel-tools/containers/CentOS9-devel.def
new file mode 100644
index 000000000..6c695dd40
--- /dev/null
+++ b/devel-tools/containers/CentOS9-devel.def
@@ -0,0 +1,48 @@
+BootStrap: docker
+From: quay.io/centos/centos:stream9
+
+
+%help
+    Development environment for CentOS Stream Linux 9
+
+
+%post
+    dnf -y update
+    dnf -y install dnf-plugins-core
+
+    dnf config-manager --set-enabled crb
+    dnf -y install \
+        https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm \
+        https://dl.fedoraproject.org/pub/epel/epel-next-release-latest-9.noarch.rpm
+
+    dnf -y install \
+        bc man-db vim emacs tcsh \
+        "@Development Tools" \
+        gcc gcc-c++ gcc-gfortran cppcheck \
+        gcc-toolset-{12,13} \
+        autoconf automake cvs git subversion mercurial \
+        cmake ccache \
+        openmpi-devel tbb-devel fftw-devel tcl-devel \
+        python3-{devel,tkinter,virtualenv,numpy,scipy} \
+        ncurses-devel \
+        rlwrap \
+        tk-devel fltk-devel \
+        mesa-dri-drivers mesa-libGL-devel libglvnd-devel \
+        libXi-devel libXinerama-devel libpng-devel \
+        netcdf-devel sqlite-devel \
+        texlive-latex texlive-epstopdf texlive-pdftex latex2html \
+        texlive-graphics texlive-metafont texlive-collection-latexrecommended \
+        texlive-collection-fontsrecommended \
+	squashfs-tools
+
+    source /etc/profile
+    module load mpi
+
+    # Build Charm++
+    umask 022
+    git clone --single-branch --depth=1 -b v7.0.0 https://github.com/UIUC-PPL/charm.git /opt/charm
+    cd /opt/charm
+    export CCACHE_DIR=/tmp
+    ./build charm++ mpi-linux-x86_64 -j\$(nproc) --with-production
+    ./build charm++ netlrts-linux-x86_64 -j\$(nproc) --with-production
+    ./build charm++ multicore-linux-x86_64 -j\$(nproc) --with-production
diff --git a/devel-tools/containers/README.md b/devel-tools/containers/README.md
new file mode 100644
index 000000000..40bd3bad8
--- /dev/null
+++ b/devel-tools/containers/README.md
@@ -0,0 +1,12 @@
+1. Install Apptainer (formerly Singularity), either from your Linux
+   distribution's package manager or from https://github.com/apptainer/apptainer/releases/
+
+2. Build a container from its definition file using:
+```
+apptainer build container.sif container.def
+```
+
+3. Run a shell inside the container:
+```
+apptainer run container.sif
+```
diff --git a/doc/cv_version.tex b/doc/cv_version.tex
index f6a2281ea..3f2af9429 100644
--- a/doc/cv_version.tex
+++ b/doc/cv_version.tex
@@ -1 +1 @@
-\newcommand{\cvversion}{2023-07-21}
+\newcommand{\cvversion}{2023-08-21}
diff --git a/C_fortran/C_test.c b/misc_interfaces/C_fortran/C_test.c
similarity index 100%
rename from C_fortran/C_test.c
rename to misc_interfaces/C_fortran/C_test.c
diff --git a/C_fortran/Makefile b/misc_interfaces/C_fortran/Makefile
similarity index 85%
rename from C_fortran/Makefile
rename to misc_interfaces/C_fortran/Makefile
index 09c2aa49d..cd5361a49 100644
--- a/C_fortran/Makefile
+++ b/misc_interfaces/C_fortran/Makefile
@@ -3,8 +3,8 @@
 # This Makefile is useful for compilation tests only.  To use the library,
 # please use instead the build recipes of the packages that include it.
 
-COLVARS_LIB = ../src/libcolvars.a
-COLVARS_SRC_DIR = ../src
+COLVARS_LIB = ../../src/libcolvars.a
+COLVARS_SRC_DIR = ../../src
 IF_OBJ = colvarproxy_C.o
 
 CXXFLAGS := -std=c++11 -pedantic -g -O2 -fPIC
@@ -26,7 +26,7 @@ C_test.o: C_test.c
 	gcc -c $< -pedantic -g  -I$(COLVARS_SRC_DIR)
 
 $(COLVARS_LIB):
-	make -f $(COLVARS_SRC_DIR)/Makefile -C $(COLVARS_SRC_DIR) libcolvars.a -j20
+	make -C $(COLVARS_SRC_DIR) libcolvars.a -j20
 
 %.o: %.cpp
 	$(CXX) $(CXXFLAGS) -c -o $@ $<  -I$(COLVARS_SRC_DIR)
diff --git a/C_fortran/colvarproxy_C.cpp b/misc_interfaces/C_fortran/colvarproxy_C.cpp
similarity index 100%
rename from C_fortran/colvarproxy_C.cpp
rename to misc_interfaces/C_fortran/colvarproxy_C.cpp
diff --git a/C_fortran/colvarproxy_C.h b/misc_interfaces/C_fortran/colvarproxy_C.h
similarity index 98%
rename from C_fortran/colvarproxy_C.h
rename to misc_interfaces/C_fortran/colvarproxy_C.h
index 39946a465..8babb0c42 100644
--- a/C_fortran/colvarproxy_C.h
+++ b/misc_interfaces/C_fortran/colvarproxy_C.h
@@ -1,6 +1,7 @@
 // Test linking Colvars through a C interface
 
 #include "colvarproxy.h"
+#include <iostream>
 
 /// \brief Communication between colvars and LAMMPS
 /// (implementation of \link colvarproxy \endlink)
diff --git a/C_fortran/colvarproxy_C_interface.h b/misc_interfaces/C_fortran/colvarproxy_C_interface.h
similarity index 100%
rename from C_fortran/colvarproxy_C_interface.h
rename to misc_interfaces/C_fortran/colvarproxy_C_interface.h
diff --git a/C_fortran/colvars.py b/misc_interfaces/C_fortran/colvars.py
similarity index 100%
rename from C_fortran/colvars.py
rename to misc_interfaces/C_fortran/colvars.py
diff --git a/C_fortran/fortran_test.f90 b/misc_interfaces/C_fortran/fortran_test.f90
similarity index 100%
rename from C_fortran/fortran_test.f90
rename to misc_interfaces/C_fortran/fortran_test.f90
diff --git a/python/colvars.py b/misc_interfaces/python/colvars.py
similarity index 100%
rename from python/colvars.py
rename to misc_interfaces/python/colvars.py
diff --git a/tests/stubs/colvarproxy_stub.cpp b/misc_interfaces/stubs/colvarproxy_stub.cpp
similarity index 100%
rename from tests/stubs/colvarproxy_stub.cpp
rename to misc_interfaces/stubs/colvarproxy_stub.cpp
diff --git a/tests/stubs/colvarproxy_stub.h b/misc_interfaces/stubs/colvarproxy_stub.h
similarity index 100%
rename from tests/stubs/colvarproxy_stub.h
rename to misc_interfaces/stubs/colvarproxy_stub.h
diff --git a/src/colvarbias.cpp b/src/colvarbias.cpp
index 18969fc53..97c0c40e4 100644
--- a/src/colvarbias.cpp
+++ b/src/colvarbias.cpp
@@ -462,17 +462,15 @@ std::string const colvarbias::get_state_params() const
 }
 
 
-int colvarbias::set_state_params(std::string const &conf)
+int colvarbias::check_matching_state(std::string const &conf)
 {
-  matching_state = false;
-
   std::string check_name = "";
   colvarparse::get_keyval(conf, "name", check_name,
                           std::string(""), colvarparse::parse_silent);
 
   if (check_name.size() == 0) {
-    cvm::error("Error: \""+bias_type+"\" block within the restart file "
-               "has no identifiers.\n", COLVARS_INPUT_ERROR);
+    return cvm::error("Error: \""+bias_type+"\" block within the state file "
+                      "has no identifiers.\n", COLVARS_INPUT_ERROR);
   }
 
   if (check_name != this->name) {
@@ -480,11 +478,17 @@ int colvarbias::set_state_params(std::string const &conf)
       cvm::log("Ignoring state of bias \""+check_name+
                "\": this bias is named \""+name+"\".\n");
     }
-    return COLVARS_OK;
+    matching_state = false;
+  } else {
+    matching_state = true;
   }
 
-  matching_state = true;
+  return COLVARS_OK;
+}
+
 
+int colvarbias::set_state_params(std::string const &conf)
+{
   colvarparse::get_keyval(conf, "step", state_file_step,
                           cvm::step_absolute(), colvarparse::parse_silent);
 
@@ -515,41 +519,42 @@ std::ostream & colvarbias::write_state(std::ostream &os)
 
 std::istream & colvarbias::read_state(std::istream &is)
 {
-  std::streampos const start_pos = is.tellg();
+  auto const start_pos = is.tellg();
 
   std::string key, brace, conf;
   if ( !(is >> key)   || !(key == state_keyword || key == bias_type) ||
        !(is >> brace) || !(brace == "{") ||
        !(is >> colvarparse::read_block("configuration", &conf)) ||
-       (set_state_params(conf) != COLVARS_OK) ) {
+       (check_matching_state(conf) != COLVARS_OK) ) {
     cvm::error("Error: in reading state configuration for \""+bias_type+
                "\" bias \""+
                this->name+"\" at position "+
                cvm::to_str(static_cast<size_t>(is.tellg()))+
                " in stream.\n", COLVARS_INPUT_ERROR);
     is.clear();
-    is.seekg(start_pos, std::ios::beg);
+    is.seekg(start_pos);
     is.setstate(std::ios::failbit);
     return is;
   }
 
-  if (matching_state == false) {
-    // This state is not for this bias
-    is.seekg(start_pos, std::ios::beg);
+  if (!matching_state) {
+    // No errors reading, but this state is not for this bias; rewind
+    is.seekg(start_pos);
     return is;
   }
 
   cvm::log("Restarting "+bias_type+" bias \""+name+"\" from step number "+
            cvm::to_str(state_file_step)+".\n");
 
-  if (!read_state_data(is)) {
+  if ((set_state_params(conf) != COLVARS_OK) || !read_state_data(is)) {
     cvm::error("Error: in reading state data for \""+bias_type+"\" bias \""+
                this->name+"\" at position "+
                cvm::to_str(static_cast<size_t>(is.tellg()))+
                " in stream.\n", COLVARS_INPUT_ERROR);
+    auto state = is.rdstate();
     is.clear();
-    is.seekg(start_pos, std::ios::beg);
-    is.setstate(std::ios::failbit);
+    is.seekg(start_pos);
+    is.setstate(state);
   }
 
   is >> brace;
diff --git a/src/colvarbias.h b/src/colvarbias.h
index e865902be..de7b04b51 100644
--- a/src/colvarbias.h
+++ b/src/colvarbias.h
@@ -133,6 +133,9 @@ class colvarbias
   /// Write the values of specific mutable properties to a string
   virtual std::string const get_state_params() const;
 
+  /// Check the name of the bias vs. the given string, set the matching_state flag accordingly
+  int check_matching_state(std::string const &conf);
+
   /// Read the values of specific mutable properties from a string
   virtual int set_state_params(std::string const &state_conf);
 
diff --git a/src/colvarcomp.cpp b/src/colvarcomp.cpp
index abe522a24..151a25569 100644
--- a/src/colvarcomp.cpp
+++ b/src/colvarcomp.cpp
@@ -43,6 +43,22 @@ colvar::cvc::cvc(std::string const &conf)
 }
 
 
+int colvar::cvc::update_description()
+{
+  if (name.size() > 0) {
+    description = "cvc " + name;
+  } else {
+    description = "unnamed cvc";
+  }
+  if (function_type.size() > 0) {
+    description += " of type \"" + function_type + "\"";
+  } else {
+    description += " of unset type";
+  }
+  return COLVARS_OK;
+}
+
+
 int colvar::cvc::set_function_type(std::string const &type)
 {
   function_type = type;
@@ -53,6 +69,8 @@ int colvar::cvc::set_function_type(std::string const &type)
       function_types.push_back(function_type);
     }
   }
+  update_description();
+
   for (size_t i = function_types.size()-1; i > 0; i--) {
     cvm::main()->cite_feature(function_types[i]+" colvar component"+
                               " (derived from "+function_types[i-1]+")");
@@ -74,11 +92,6 @@ int colvar::cvc::init(std::string const &conf)
   }
 
   if (get_keyval(conf, "name", name, name)) {
-    if (name.size() > 0) {
-      description = "cvc \"" + name + "\" of type " + function_type;
-    } else {
-      description = "unnamed cvc";
-    }
     if ((name != old_name) && (old_name.size() > 0)) {
       cvm::error("Error: cannot rename component \""+old_name+
                  "\" after initialization (new name = \""+name+"\")",
@@ -86,6 +99,7 @@ int colvar::cvc::init(std::string const &conf)
       name = old_name;
     }
   }
+  update_description();
 
   get_keyval(conf, "componentCoeff", sup_coeff, sup_coeff);
   get_keyval(conf, "componentExp", sup_np, sup_np);
@@ -314,7 +328,7 @@ int colvar::cvc::init_dependencies() {
 
 int colvar::cvc::setup()
 {
-  description = "cvc " + name;
+  update_description();
   return COLVARS_OK;
 }
 
diff --git a/src/colvarcomp.h b/src/colvarcomp.h
index c89143bc0..e475d815c 100644
--- a/src/colvarcomp.h
+++ b/src/colvarcomp.h
@@ -278,6 +278,9 @@ class colvar::cvc
 
 protected:
 
+  /// Update the description string based on name and type
+  int update_description();
+
   /// Record the type of this class as well as those it is derived from
   std::vector<std::string> function_types;
 
diff --git a/src/colvarcomp_combination.cpp b/src/colvarcomp_combination.cpp
index 7d5079701..974cc870c 100644
--- a/src/colvarcomp_combination.cpp
+++ b/src/colvarcomp_combination.cpp
@@ -33,22 +33,8 @@ colvar::linearCombination::linearCombination(std::string const &conf): cvc(conf)
                    " expects one or more nesting components.\n");
         return;
     } else {
-        // TODO: Maybe we can add an option to allow mixing scalar and vector types,
-        //       but that's a bit complicated so we just require a consistent type
-        //       of nesting CVs.
         x.type(cv[0]->value());
         x.reset();
-        for (size_t i_cv = 1; i_cv < cv.size(); ++i_cv) {
-            const auto type_i = cv[i_cv]->value().type();
-            if (type_i != x.type()) {
-                cvm::error("Error: the type of sub-CVC " + cv[i_cv]->name +
-                          " is " + colvarvalue::type_desc(type_i) + ", which is "
-                          "different to the type of the first sub-CVC. Currently "
-                          "only sub-CVCs of the same type are supported to be "
-                          "nested.\n");
-                return;
-            }
-        }
     }
     use_explicit_gradients = true;
     for (size_t i_cv = 0; i_cv < cv.size(); ++i_cv) {
@@ -317,7 +303,8 @@ void colvar::customColvar::apply_force(colvarvalue const &force) {
                 }
             } else {
                 const colvarvalue& current_cv_value = cv[i_cv]->value();
-                colvarvalue cv_force(current_cv_value.type());
+                colvarvalue cv_force(current_cv_value);
+                cv_force.reset();
                 const cvm::real factor_polynomial = getPolynomialFactorOfCVGradient(i_cv);
                 for (size_t j_elem = 0; j_elem < current_cv_value.size(); ++j_elem) {
                     for (size_t c = 0; c < x.size(); ++c) {
diff --git a/src/colvars_version.h b/src/colvars_version.h
index d0f63e717..0aa4e60d1 100644
--- a/src/colvars_version.h
+++ b/src/colvars_version.h
@@ -1,3 +1,3 @@
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2023-07-21"
+#define COLVARS_VERSION "2023-08-21"
 #endif
diff --git a/src/colvarvalue.h b/src/colvarvalue.h
index 9ab8dbe31..6bc7a57c7 100644
--- a/src/colvarvalue.h
+++ b/src/colvarvalue.h
@@ -120,7 +120,8 @@ class colvarvalue {
   /// number and always behaves like it unless you change its type
   colvarvalue();
 
-  /// Constructor from a type specification
+  /// Constructor from a type flag (note: type_vector also needs the vector length to be set)
+  /// \param[in] vti Value of the \link Type \endlink enum
   colvarvalue(Type const &vti);
 
   /// Copy constructor from real base type
diff --git a/tests/functional/CMakeLists.txt b/tests/functional/CMakeLists.txt
index e86a6228d..cfcade4d9 100644
--- a/tests/functional/CMakeLists.txt
+++ b/tests/functional/CMakeLists.txt
@@ -1,4 +1,4 @@
-set(COLVARS_STUBS_DIR ${COLVARS_SOURCE_DIR}/tests/stubs/)
+set(COLVARS_STUBS_DIR ${COLVARS_SOURCE_DIR}/misc_interfaces/stubs/)
 add_library(colvars_stubs OBJECT ${COLVARS_STUBS_DIR}/colvarproxy_stub.cpp)
 target_include_directories(colvars_stubs PRIVATE ${COLVARS_SOURCE_DIR}/src)
 
diff --git a/tests/unittests/CMakeLists.txt b/tests/unittests/CMakeLists.txt
index f4653cb2b..e2804ae75 100644
--- a/tests/unittests/CMakeLists.txt
+++ b/tests/unittests/CMakeLists.txt
@@ -17,7 +17,7 @@ endif()
 
 # Last test requires the stubs proxy
 add_executable(read_xyz_traj read_xyz_traj.cpp)
-set(COLVARS_STUBS_DIR ${COLVARS_SOURCE_DIR}/tests/stubs/)
+set(COLVARS_STUBS_DIR ${COLVARS_SOURCE_DIR}/misc_interfaces/stubs/)
 target_link_libraries(read_xyz_traj PRIVATE colvars colvars_stubs)
 target_include_directories(read_xyz_traj PRIVATE ${COLVARS_SOURCE_DIR}/src)
 target_include_directories(read_xyz_traj PRIVATE ${COLVARS_STUBS_DIR})
diff --git a/update-colvars-code.sh b/update-colvars-code.sh
index 8c9a9ea80..8932391de 100755
--- a/update-colvars-code.sh
+++ b/update-colvars-code.sh
@@ -1,6 +1,8 @@
 #!/bin/bash
 # -*- sh-basic-offset: 2; sh-indentation: 2; -*-
 
+set -e
+
 # Script to update a NAMD, VMD, LAMMPS or GROMACS source tree with the latest Colvars
 # version.
 
@@ -363,7 +365,7 @@ then
   condcopy "${source}/namd/lepton/Makefile.namd" \
            "${target}/lepton/Makefile.namd"
 
-  if ! grep -q lepton/Makefile.namd "${target}/lepton/Makefile.namd" ; then
+  if ! grep -q lepton/Makefile.namd "${target}/Makefile" ; then
     patch -p1 -N -d ${target} < namd/Makefile.patch
   fi