diff --git a/.github/workflows/ci_cmake.yml b/.github/workflows/ci_cmake.yml
index 10a144ff..a9f35458 100644
--- a/.github/workflows/ci_cmake.yml
+++ b/.github/workflows/ci_cmake.yml
@@ -22,7 +22,7 @@ jobs:
   linux:
     runs-on: ubuntu-22.04
     name: CMake build on Linux
-    timeout-minutes: 15
+    timeout-minutes: 60
 
     strategy:
       matrix:
@@ -92,16 +92,16 @@ jobs:
 
     - name: Upload package
       if: github.event.action == 'published'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: binary-archive
+        name: linux-binary-archive-${{ matrix.cc }}-${{ matrix.mpi }}-shared-${{ matrix.shared }}
         path: build/package
 
     - name: Upload log files
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: linux_cmake_log
+        name: linux_cmake_log-${{ matrix.cc }}-${{ matrix.mpi }}-shared-${{ matrix.shared }}
         path: |
           ./build/CMakeFiles/CMakeConfigureLog.yaml
           ./build/Testing/Temporary/LastTest.log
@@ -110,7 +110,7 @@ jobs:
     needs: linux
     runs-on: ubuntu-22.04
     name: CMake with Valgrind
-    timeout-minutes: 15
+    timeout-minutes: 60
 
     strategy:
       matrix:
@@ -143,7 +143,7 @@ jobs:
 
     - name: Upload log files
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: linux_cmake_valgrind_log
         path: |
@@ -151,9 +151,11 @@ jobs:
           ./build/Testing/Temporary/LastTest.log
 
   mac:
-    runs-on: macos-latest
+    # macos-14 is to use Apple Silicon hardware as most Apple users nowadays would have
+    # https://github.blog/changelog/2024-01-30-github-actions-introducing-the-new-m1-macos-runner-available-to-open-source/
+    runs-on: macos-14
     name: CMake build on MacOS
-    timeout-minutes: 15
+    timeout-minutes: 60
 
     strategy:
       matrix:
@@ -198,16 +200,16 @@ jobs:
 
     - name: Upload package
       if: github.event.action == 'published'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: binary-archive
+        name: mac-binary-archive-${{ matrix.cc }}-shared-${{ matrix.shared }}
         path: build/package
 
     - name: Upload log files
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: mac_cmake_log
+        name: mac_cmake_log-${{ matrix.cc }}-shared-${{ matrix.shared }}
         path: |
           ./build/CMakeFiles/CMakeConfigureLog.yaml
           ./build/Testing/Temporary/LastTest.log
@@ -215,7 +217,7 @@ jobs:
   windows:
     runs-on: windows-latest
     name: CMake build on Windows
-    timeout-minutes: 20
+    timeout-minutes: 60
 
     strategy:
       matrix:
@@ -253,14 +255,14 @@ jobs:
 
     - name: Upload package
       if: github.event.action == 'published'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: binary-archive
+        name: windows-binary-archive
         path: build/package
 
     - name: Upload log files
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: windows_cmake_log
         path: |
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 67d7cd28..9ebf6efb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -54,7 +54,7 @@ $<$<BOOL:${SC_NEED_M}>:m>
 $<$<BOOL:${WIN32}>:${WINSOCK_LIBRARIES}>
 )
 
-# imported target, for use from FetchContent
+# imported target, for use from parent project
 add_library(SC::SC INTERFACE IMPORTED GLOBAL)
 target_link_libraries(SC::SC INTERFACE sc)
 
diff --git a/CMakePresets.json b/CMakePresets.json
index 966cd383..62fc934a 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -30,7 +30,7 @@
     "noTestsAction": "error",
     "scheduleRandom": true,
     "stopOnFailure": false,
-    "timeout": 30
+    "timeout": 60
   },
   "filter": {
     "exclude": {
diff --git a/cmake/config.cmake b/cmake/config.cmake
index d311775a..74d4f6de 100644
--- a/cmake/config.cmake
+++ b/cmake/config.cmake
@@ -49,11 +49,16 @@ endif()
 
 find_package(Threads)
 
-find_package(jansson CONFIG)
-if(TARGET jansson::jansson)
-  set(SC_HAVE_JSON 1 CACHE BOOL "JSON features enabled")
+if(json)
+  message(STATUS "Using builtin jansson")
+  include(${CMAKE_CURRENT_LIST_DIR}/jansson.cmake)
 else()
-  set(SC_HAVE_JSON 0 CACHE BOOL "JSON features disabled")
+  find_package(jansson CONFIG)
+  if(TARGET jansson::jansson)
+    set(SC_HAVE_JSON 1 CACHE BOOL "JSON features enabled")
+  else()
+    set(SC_HAVE_JSON 0 CACHE BOOL "JSON features disabled")
+  endif()
 endif()
 # --- set global compile environment
 
@@ -74,6 +79,7 @@ if(mpi)
   set(SC_CC \"${MPI_C_COMPILER}\")
   set(SC_CPP ${MPI_C_COMPILER})
 else()
+  set(SC_ENABLE_MPI 0)
   set(SC_CC \"${CMAKE_C_COMPILER}\")
   set(SC_CPP ${CMAKE_C_COMPILER})
 endif()
@@ -104,7 +110,16 @@ endif()
 set(SC_ENABLE_PTHREAD ${CMAKE_USE_PTHREADS_INIT})
 set(SC_ENABLE_MEMALIGN 1)
 
-if(mpi)
+if(NOT SC_ENABLE_MPI EQUAL CACHE{SC_ENABLE_MPI})
+  # user has requested a different MPI setting, so we need to clear these cache variables to recheck
+  unset(SC_ENABLE_MPICOMMSHARED CACHE)
+  unset(SC_ENABLE_MPITHREAD CACHE)
+  unset(SC_ENABLE_MPIWINSHARED CACHE)
+  unset(SC_ENABLE_MPIIO CACHE)
+  unset(SC_ENABLE_MPI CACHE)
+endif()
+
+if(SC_ENABLE_MPI)
   check_symbol_exists(MPI_COMM_TYPE_SHARED mpi.h SC_ENABLE_MPICOMMSHARED)
   # perform check to set SC_ENABLE_MPIIO
   include(cmake/check_mpiio.cmake)
@@ -201,9 +216,8 @@ endif()
 check_type_size(int SC_SIZEOF_INT BUILTIN_TYPES_ONLY)
 check_type_size("unsigned int" SC_SIZEOF_UNSIGNED_INT BUILTIN_TYPES_ONLY)
 check_type_size(long SC_SIZEOF_LONG BUILTIN_TYPES_ONLY)
-check_type_size("long long" SC_SIZEOF_LONG_LONG BUILTIN_TYPES_ONLY)
 check_type_size("unsigned long" SC_SIZEOF_UNSIGNED_LONG BUILTIN_TYPES_ONLY)
-check_type_size("unsigned long long" SC_SIZEOF_UNSIGNED_LONG_LONG BUILTIN_TYPES_ONLY)
+check_type_size("long long" SC_SIZEOF_LONG_LONG BUILTIN_TYPES_ONLY)
 set(SC_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
 
 if(CMAKE_BUILD_TYPE MATCHES "Debug")
@@ -214,6 +228,9 @@ endif()
 
 configure_file(${CMAKE_CURRENT_LIST_DIR}/sc_config.h.in ${PROJECT_BINARY_DIR}/include/sc_config.h)
 
+file(TIMESTAMP ${PROJECT_BINARY_DIR}/include/sc_config.h _t)
+message(VERBOSE "sc_config.h was last generated ${_t}")
+
 # --- sanity check of MPI sc_config.h
 
 unset(SC_ENABLE_MPI)
@@ -226,9 +243,17 @@ set(CMAKE_REQUIRED_LIBRARIES)
 set(CMAKE_REQUIRED_DEFINITIONS)
 
 # libsc and current project must both be compiled with/without MPI
-check_symbol_exists(SC_ENABLE_MPI ${PROJECT_BINARY_DIR}/include/sc_config.h SC_ENABLE_MPI)
-check_symbol_exists(SC_ENABLE_MPIIO ${PROJECT_BINARY_DIR}/include/sc_config.h SC_ENABLE_MPIIO)
+check_symbol_exists("SC_ENABLE_MPI" ${PROJECT_BINARY_DIR}/include/sc_config.h SC_ENABLE_MPI)
+check_symbol_exists("SC_ENABLE_MPIIO" ${PROJECT_BINARY_DIR}/include/sc_config.h SC_ENABLE_MPIIO)
 
+# check consistency of MPI configuration
 if(mpi AND NOT (SC_ENABLE_MPI AND SC_ENABLE_MPIIO))
   message(FATAL_ERROR "libsc MPI support was requested, but not configured in ${PROJECT_BINARY_DIR}/include/sc_config.h")
 endif()
+
+# check consistency of MPI I/O configuration
+if(mpi AND (SC_ENABLE_MPI AND NOT SC_ENABLE_MPIIO))
+  message(WARNING "libsc MPI configured but MPI I/O is not configured/found: DEPRECATED")
+  message(NOTICE "This configuration is DEPRECATED and will be disallowed in the future.")
+  message(NOTICE "If the MPI File API is not available, please disable MPI altogether.")
+endif()
diff --git a/cmake/git.cmake b/cmake/git.cmake
index f88e9846..4718b8e9 100644
--- a/cmake/git.cmake
+++ b/cmake/git.cmake
@@ -5,7 +5,7 @@ set(PROJECT_MINOR 0)
 set(PROJECT_PATCH 0)
 set(PROJECT_VERSION 0.0.0)
 find_program(GIT_VERSION_GEN NAMES git-version-gen
-             PATHS ${CMAKE_SOURCE_DIR}/build-aux NO_DEFAULT_PATH)
+             PATHS ${PROJECT_SOURCE_DIR}/build-aux NO_DEFAULT_PATH)
 if(GIT_VERSION_GEN)
   execute_process(COMMAND ${GIT_VERSION_GEN} .tarball-version
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
diff --git a/cmake/jansson.cmake b/cmake/jansson.cmake
new file mode 100644
index 00000000..df2ce358
--- /dev/null
+++ b/cmake/jansson.cmake
@@ -0,0 +1,52 @@
+include(ExternalProject)
+include(GNUInstallDirs)
+
+set(SC_HAVE_JSON 1 CACHE BOOL "using SC-built JANSSON")
+
+set(jansson_url "https://github.com/akheron/jansson/releases/download/v2.14/jansson-2.14.tar.bz2")
+
+set(JANSSON_INCLUDE_DIRS ${CMAKE_INSTALL_PREFIX}/include)
+
+if(BUILD_SHARED_LIBS)
+  if(WIN32)
+    set(JANSSON_LIBRARIES ${CMAKE_INSTALL_FULL_BINDIR}/${CMAKE_SHARED_LIBRARY_PREFIX}jansson${CMAKE_SHARED_LIBRARY_SUFFIX})
+  else()
+    set(JANSSON_LIBRARIES ${CMAKE_INSTALL_FULL_LIBDIR}/${CMAKE_SHARED_LIBRARY_PREFIX}jansson${CMAKE_SHARED_LIBRARY_SUFFIX})
+  endif()
+else()
+    set(JANSSON_LIBRARIES ${CMAKE_INSTALL_FULL_LIBDIR}/${CMAKE_STATIC_LIBRARY_PREFIX}jansson${CMAKE_STATIC_LIBRARY_SUFFIX})
+endif()
+
+set(jansson_cmake_args
+-DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_INSTALL_PREFIX}
+-DJANSSON_BUILD_SHARED_LIBS:BOOL=${BUILD_SHARED_LIBS}
+-DCMAKE_BUILD_TYPE=Release
+-DJANSSON_EXAMPLES:BOOL=off
+-DJANSSON_WITHOUT_TESTS:BOOL=on
+-DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
+-DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+)
+
+ExternalProject_Add(JANSSON
+URL ${jansson_url}
+CMAKE_ARGS ${jansson_cmake_args}
+BUILD_BYPRODUCTS ${JANSSON_LIBRARIES}
+CONFIGURE_HANDLED_BY_BUILD ON
+USES_TERMINAL_DOWNLOAD true
+USES_TERMINAL_UPDATE true
+USES_TERMINAL_CONFIGURE true
+USES_TERMINAL_BUILD true
+USES_TERMINAL_INSTALL true
+USES_TERMINAL_TEST true
+)
+
+
+# --- imported target
+
+file(MAKE_DIRECTORY ${JANSSON_INCLUDE_DIRS})
+# avoid race condition
+
+add_library(jansson::jansson INTERFACE IMPORTED GLOBAL)
+add_dependencies(jansson::jansson JANSSON)  # to avoid include directory race condition
+target_link_libraries(jansson::jansson INTERFACE ${JANSSON_LIBRARIES})
+target_include_directories(jansson::jansson INTERFACE ${JANSSON_INCLUDE_DIRS})
diff --git a/cmake/options.cmake b/cmake/options.cmake
index a7bab317..48145398 100644
--- a/cmake/options.cmake
+++ b/cmake/options.cmake
@@ -1,6 +1,8 @@
 option(mpi "use MPI library" off)
 option(openmp "use OpenMP" off)
 option(zlib "build ZLIB" off)
+option(json "build Jansson" off)
+
 option(SC_BUILD_TESTING "build libsc self-tests" on)
 option(TEST_WITH_VALGRIND "run self-tests with valgrind" OFF)
 option(BUILD_SHARED_LIBS "build shared libsc")
diff --git a/cmake/sc_config.h.in b/cmake/sc_config.h.in
index 481e9ff9..d4d05f49 100644
--- a/cmake/sc_config.h.in
+++ b/cmake/sc_config.h.in
@@ -213,14 +213,11 @@
 #ifndef SC_SIZEOF_LONG
 #define SC_SIZEOF_LONG @SC_SIZEOF_LONG@
 #endif
-#ifndef SC_SIZEOF_LONG_LONG
-#define SC_SIZEOF_LONG_LONG @SC_SIZEOF_LONG_LONG@
-#endif
 #ifndef SC_SIZEOF_UNSIGNED_LONG
 #define SC_SIZEOF_UNSIGNED_LONG @SC_SIZEOF_UNSIGNED_LONG@
 #endif
-#ifndef SC_SIZEOF_UNSIGNED_LONG_LONG
-#define SC_SIZEOF_UNSIGNED_LONG_LONG @SC_SIZEOF_UNSIGNED_LONG_LONG@
+#ifndef SC_SIZEOF_LONG_LONG
+#define SC_SIZEOF_LONG_LONG @SC_SIZEOF_LONG_LONG@
 #endif
 
 /* The size of `void *', as computed by sizeof. */
diff --git a/cmake/zlib.cmake b/cmake/zlib.cmake
index 15d7dfd5..c5bd7563 100644
--- a/cmake/zlib.cmake
+++ b/cmake/zlib.cmake
@@ -6,7 +6,7 @@ set(SC_HAVE_ZLIB 1 CACHE BOOL "using SC-built Zlib")
 # default zlib source archive
 if (NOT DEFINED SC_BUILD_ZLIB_ARCHIVE_FILE)
   if (NOT DEFINED SC_BUILD_ZLIB_VERSION)
-    set(SC_BUILD_ZLIB_VERSION 2.1.5)
+    set(SC_BUILD_ZLIB_VERSION 2.1.6)
   endif()
   set(SC_BUILD_ZLIB_ARCHIVE_FILE https://github.com/zlib-ng/zlib-ng/archive/refs/tags/${SC_BUILD_ZLIB_VERSION}.tar.gz CACHE STRING "zlib source archive (URL or local filepath).")
 endif()
@@ -43,7 +43,6 @@ URL ${SC_BUILD_ZLIB_ARCHIVE_FILE}
 CMAKE_ARGS ${zlib_cmake_args}
 BUILD_BYPRODUCTS ${ZLIB_LIBRARIES}
 CONFIGURE_HANDLED_BY_BUILD ON
-INACTIVITY_TIMEOUT 60
 USES_TERMINAL_DOWNLOAD true
 USES_TERMINAL_UPDATE true
 USES_TERMINAL_CONFIGURE true
diff --git a/config/sc_include.m4 b/config/sc_include.m4
index 90d468b7..02fb9737 100644
--- a/config/sc_include.m4
+++ b/config/sc_include.m4
@@ -1,4 +1,4 @@
-
+dnl
 dnl sc_include.m4 - general custom macros
 dnl
 dnl This file is part of the SC Library.
@@ -8,6 +8,18 @@ dnl Copyright (C) 2008,2009 Carsten Burstedde, Lucas Wilcox.
 
 dnl Documentation for macro names: brackets indicate optional arguments
 
+dnl SC_SINGLE_LINE
+dnl Print 72 characters '-' without any trailing newline.
+AC_DEFUN([SC_SINGLE_LINE],[dnl
+------------------------------------------------------------------------dnl
+])
+
+dnl SC_DOUBLE_LINE
+dnl Print 72 characters '=' without any trailing newline.
+AC_DEFUN([SC_DOUBLE_LINE],[dnl
+========================================================================dnl
+])
+
 dnl SC_VERSION(PREFIX)
 dnl Expose major, minor, and point version numbers as CPP defines.
 dnl Also creates a makefile variable PACKAGE_PREFIX with value PREFIX.
@@ -406,9 +418,15 @@ dnl This macro prints messages at the end of the configure run.
 dnl
 AC_DEFUN([SC_FINAL_MESSAGES],
 [
+if test "x$HAVE_PKG_MPI" = xyes && test "x$HAVE_PKG_MPIIO" != xyes ; then
+AC_MSG_NOTICE([SC_SINGLE_LINE
+$1 has been configured --enable-mpi and --disable-mpiio.
+This configuration is DEPRECATED and will be disallowed in the future.
+If the MPI File API is not available, please configure to --disable-mpi.])
+fi
 if test "x$$1_HAVE_ZLIB" = x ; then
-AC_MSG_NOTICE([- $1 ----------------------------------------------------
-We did not find a recent zlib containing the function adler32_combine.
+AC_MSG_NOTICE([SC_SINGLE_LINE
+$1 did not find a recent zlib containing the function adler32_combine.
 This is OK if the following does not matter to you:
  - Calling some functions that rely on zlib will abort your program.
    These include sc_array_checksum and sc_vtk_write_compressed.
@@ -417,9 +435,10 @@ This is OK if the following does not matter to you:
 You can fix this by compiling a recent zlib and pointing LIBS to it.])
 fi
 if test "x$$1_HAVE_JSON" = x ; then
-AC_MSG_NOTICE([- $1 ----------------------------------------------------
-We did not find a JSON library containing json_integer and json_real.
+AC_MSG_NOTICE([SC_SINGLE_LINE
+$1 did not find a JSON library containing json_integer and json_real.
 This means that loading JSON files for option values will fail.
 You can fix this by installing the jansson development library.])
 fi
+AC_MSG_NOTICE([SC_SINGLE_LINE])
 ])
diff --git a/config/sc_mpi.m4 b/config/sc_mpi.m4
index cd158b8a..ad1af6ed 100644
--- a/config/sc_mpi.m4
+++ b/config/sc_mpi.m4
@@ -12,6 +12,7 @@ dnl                   on the configure command line.
 dnl                   Likewise for F77, FC and CXX if enabled in SC_MPI_CONFIG.
 dnl --disable-mpiio   Only effective if --enable-mpi is given.  In this case,
 dnl                   do not use MPI I/O in sc and skip the compile-and-link test.
+dnl                   DEPRECATED: we will disallow this combination in the future.
 dnl --disable-mpithread Only effective if --enable-mpi is given.  In this case,
 dnl                   do not use MPI_Init_thread () and skip compile-and-link test.
 dnl --disable-mpishared Only effective if --enable-mpi is given.  In this case,
@@ -71,14 +72,14 @@ dnl The shell variable SC_ENABLE_MPIIO is set if --disable-mpiio is not given.
 dnl If not disabled, MPI I/O will be verified by a compile/link test below.
 AC_ARG_ENABLE([mpiio],
               [AS_HELP_STRING([--disable-mpiio],
-               [do not use MPI I/O (even if MPI is enabled)])],,
+               [do not use MPI I/O (this option is DEPRECATED)])],,
               [enableval=yes])
 if test "x$enableval" = xyes ; then
   if test "x$HAVE_PKG_MPI" = xyes ; then
     HAVE_PKG_MPIIO=yes
   fi
 elif test "x$enableval" != xno ; then
-  AC_MSG_WARN([Ignoring --enable-mpiio with unsupported argument])
+  AC_MSG_ERROR([use --disable-mpiio without an argument (option DEPRECATED)])
 fi
 AC_MSG_CHECKING([whether we are using MPI I/O])
 AC_MSG_RESULT([$HAVE_PKG_MPIIO])
@@ -279,6 +280,7 @@ AC_LINK_IFELSE([AC_LANG_PROGRAM(
 int mpiret =
 MPI_Init ((int *) 0, (char ***) 0);
 if (mpiret == MPI_ERR_ARG ||
+    mpiret == MPI_ERR_COUNT ||
     mpiret == MPI_ERR_UNKNOWN ||
     mpiret == MPI_ERR_OTHER ||
     mpiret == MPI_ERR_NO_MEM) {
@@ -513,7 +515,7 @@ dnl  ])
   ])
   if test "x$HAVE_PKG_MPIIO" = xyes ; then
     SC_MPIIO_C_COMPILE_AND_LINK(,
-      [AC_MSG_ERROR([MPI I/O not found; you may try --disable-mpiio])])
+      [AC_MSG_ERROR([MPI I/O not found; you may --disable-mpi altogether])])
   fi
   if test "x$HAVE_PKG_MPITHREAD" = xyes ; then
     SC_MPITHREAD_C_COMPILE_AND_LINK(,
diff --git a/config/sc_soversion.in b/config/sc_soversion.in
index 50f3968c..507e077d 100644
--- a/config/sc_soversion.in
+++ b/config/sc_soversion.in
@@ -4,4 +4,4 @@
 
 # This file is included by src/Makefile.am and parsed by cmake/config.cmake.
 
-SC_SOVERSION = 2:0:0
+SC_SOVERSION = 3:0:0
diff --git a/configure.ac b/configure.ac
index f543dba7..3135c2bd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -66,9 +66,8 @@ AC_C_RESTRICT
 AC_CHECK_SIZEOF([int])
 AC_CHECK_SIZEOF([unsigned int])
 AC_CHECK_SIZEOF([long])
-AC_CHECK_SIZEOF([long long])
 AC_CHECK_SIZEOF([unsigned long])
-AC_CHECK_SIZEOF([unsigned long long])
+AC_CHECK_SIZEOF([long long])
 AC_CHECK_SIZEOF([void *])
 AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T
diff --git a/doc/author_dreyer.txt b/doc/author_dreyer.txt
new file mode 100644
index 00000000..fd9aca27
--- /dev/null
+++ b/doc/author_dreyer.txt
@@ -0,0 +1 @@
+I place my contributions to libsc under the FreeBSD license. Lukas Dreyer <lukas.dreyer@dlr.de>
diff --git a/doc/libsc-build-wdeps.sh b/doc/libsc-build-wdeps.sh
index 798bb274..2015e62b 100755
--- a/doc/libsc-build-wdeps.sh
+++ b/doc/libsc-build-wdeps.sh
@@ -13,10 +13,6 @@
 # set installation root to local subdirectory
 PREFIX="$PWD/local"
 
-# download zlib
-ZVER=1.3
-ZSHA=ff0ba4c292013dbc27530b3a81e1f9a813cd39de01ca5e0f8bf355702efa593e
-
 # download jansson
 JVER=2.14
 JSHA=5798d010e41cf8d76b66236cfb2f2543c8d082181d16bc3085ab49538d4b9929
@@ -33,15 +29,15 @@ bdie () {
 }
 
 # download, build and install zlib
-ZTAR="zlib-$ZVER.tar.gz"
-wget -N "https://www.zlib.net/$ZTAR"                    && \
-test `sha256sum "$ZTAR" | cut -d ' ' -f1` = "$ZSHA"     && \
+ZTAR="zlib.tar.gz"
+wget -N "https://www.zlib.net/current/$ZTAR"            && \
+ZDIR=`tar -tzf "$ZTAR" | head -1 | perl -p -e 's/.*(zlib-[\d\.]+).*/\1/'` && \
 tar -xvzf "$ZTAR"                                       && \
-cd "zlib-$ZVER"                                         && \
+cd $ZDIR                                                && \
 ./configure --prefix="$PREFIX/zlib"                     && \
 make -j install                                         && \
 cd ..                                                   && \
-rm -r "zlib-$ZVER" "$ZTAR"                              || bdie "zlib"
+rm -r "$ZDIR" "$ZTAR"                              || bdie "zlib"
 
 # download, build and install jansson
 JTAR="jansson-$JVER.tar.gz"
diff --git a/doc/mainpage.dox b/doc/mainpage.dox
index 3a3f62c9..df9ff5a7 100644
--- a/doc/mainpage.dox
+++ b/doc/mainpage.dox
@@ -55,7 +55,9 @@
  *                    compiler wrappers.  If this option is not given, wrappers
  *                    for MPI routines are used instead and the code is compiled
  *                    in serial only.
- * * `--disable-mpiio`  may be used to avoid using `MPI_File` based calls.
+ * * `--disable-mpiio`  may be used to avoid using `MPI_File` based calls. The
+                      usage of `--disable-mpiio` is deprecated and should not be
+                      used anymore.
  *
  * A typical development configure line looks as follows:
  * > `relative/path/to/configure CFLAGS="-Wall -O0 -g" --enable-mpi --enable-debug`
@@ -88,7 +90,7 @@
  * data in serial and the data can be stored element-wise compressed.
  *
  * If MPI I/O is available, it is used to write and read in
- * parallel. Otherwise, the behaviour is emulated using serial I/O and MPI.
+ * parallel. The configuration case of MPI without MPI I/O is deprecated.
  * Without MPI this module still enables the user to write and read equivalent
  * files but only in serial.
  *
diff --git a/doc/release_notes.txt b/doc/release_notes.txt
index 749d8fe7..f127813e 100644
--- a/doc/release_notes.txt
+++ b/doc/release_notes.txt
@@ -1,6 +1,10 @@
 
 # Release notes for the sc software library
 
+## Link to latest version DOI
+
+[![DOI](https://zenodo.org/badge/3974693.svg)](https://zenodo.org/doi/10.5281/zenodo.10838739)
+
 ## General
 
  - We have been reminded, for good reason, to maintain release notes.
@@ -24,23 +28,30 @@ There have been breaking changes, very strictly speaking.
 
 ### Build system
 
+ - Bump library version according to libtool to 3:0:0.
  - No longer install getopt and puff original headers.
  - Make sc_getopt.h a purely internal header file.
  - Add a generic external library installation option.
  - Add script doc/p4est-build-wdeps.sh for autotools build.
  - Further align CMake with the autoconf build system.
  - Update CMake logic to configure zlib and jansson.
- - Add CMake option to run tests with Valgrind
+ - Add CMake option to run tests with Valgrind.
+ - Warn if configuring MPI on and MPI I/O off.
 
 ### Functionality
 
- - Further align I/O wrappers with and without MPI I/O.
+ - Further align I/O wrappers with and without MPI.
+ - Change the semantic of sc_io_open to always truncate a newly created file.
  - Simplify the replacements for MPI_{read,write}_at*.
  - Further updates to the MPI I/O wrapper code.
+ - Deprecate the configuration with MPI but without MPI I/O.
+ - Remove sc_io_{write,read}_all.
  - Add sc_io_source, sink_destroy_null functions.
  - Make sure not to sc_io_source_read an array beyond its length.
  - Add sc_io_file_load, save functions and test program.
+ - Update sc_hash_array to hide much of internal state.
  - Update zlib and base64 encode/compression routines.
+ - Remove the MPI_UNSIGNED_LONG_LONG datatype wrapper.
 
 ## 2.8.5
 
diff --git a/src/sc3_mpi_types.h b/src/sc3_mpi_types.h
index 103d9f30..49051e39 100644
--- a/src/sc3_mpi_types.h
+++ b/src/sc3_mpi_types.h
@@ -89,6 +89,7 @@ typedef MPI_Op      sc3_MPI_Op_t;
 #define SC3_MPI_MAX_ERROR_STRING MPI_MAX_ERROR_STRING
 #define SC3_MPI_SUCCESS MPI_SUCCESS
 #define SC3_MPI_ERR_ARG MPI_ERR_ARG
+#define SC3_MPI_ERR_COUNT MPI_ERR_COUNT
 #define SC3_MPI_ERR_UNKNOWN MPI_ERR_UNKNOWN
 #define SC3_MPI_ERR_OTHER MPI_ERR_OTHER
 #define SC3_MPI_ERR_NO_MEM MPI_ERR_NO_MEM
@@ -119,6 +120,9 @@ typedef MPI_Op      sc3_MPI_Op_t;
 typedef enum sc3_MPI_IO_Errorcode
 {
   /* only MPI I/O error classes */
+  /* WARNING: This enum is only used in the deprecated case of activated MPI but
+   * deactivated MPI I/O.
+   */
   SC3_MPI_ERR_FILE = MPI_ERR_LASTCODE,
   SC3_MPI_ERR_NOT_SAME,
   SC3_MPI_ERR_AMODE,
@@ -195,9 +199,9 @@ sc3_MPI_Op_t;
 /** We wrap some MPI error codes and the I/O error classes. */
 typedef enum sc3_MPI_Errorcode
 {
-  /* we separate the error values from errno values */
   SC3_MPI_SUCCESS = 0,  /**< An MPI function has exited successfully. */
   SC3_MPI_ERR_ARG = 14000, /**< An MPI function encountered invalid arguments. */
+  SC3_MPI_ERR_COUNT,     /**< An MPI function encountered an invalid count argument. */
   SC3_MPI_ERR_UNKNOWN,  /**< An MPI function has produced an unknown error. */
   SC3_MPI_ERR_OTHER,    /**< An MPI function has produced some known error. */
   SC3_MPI_ERR_NO_MEM,   /**< An MPI function ran out of memory. */
diff --git a/src/sc_containers.c b/src/sc_containers.c
index 97f30947..954bae28 100644
--- a/src/sc_containers.c
+++ b/src/sc_containers.c
@@ -1523,7 +1523,7 @@ struct sc_hash_array_data
   sc_array_t         *pa;
   sc_hash_function_t  hash_fn;
   sc_equal_function_t equal_fn;
-  void               *user_data;
+  sc_hash_foreach_t   foreach_fn;
   void               *current_item;
 };
 
@@ -1545,7 +1545,7 @@ sc_hash_array_hash_fn (const void *v, const void *u)
   p = (l == -1L) ? internal_data->current_item :
     sc_array_index_ssize_t (internal_data->pa, l);
 
-  return internal_data->hash_fn (p, internal_data->user_data);
+  return internal_data->hash_fn (p, internal_data->the_hash_array.user_data);
 }
 
 static int
@@ -1562,7 +1562,8 @@ sc_hash_array_equal_fn (const void *v1, const void *v2, const void *u)
   p2 = (l2 == -1L) ? internal_data->current_item :
     sc_array_index_ssize_t (internal_data->pa, l2);
 
-  return internal_data->equal_fn (p1, p2, internal_data->user_data);
+  return internal_data->equal_fn
+    (p1, p2, internal_data->the_hash_array.user_data);
 }
 
 sc_hash_array_t    *
@@ -1573,8 +1574,9 @@ sc_hash_array_new (size_t elem_size, sc_hash_function_t hash_fn,
   sc_hash_array_data_t *had;
 
   /* save one allocation by storing the hash array inside its context */
-  had = SC_ALLOC (sc_hash_array_data_t, 1);
+  had = SC_ALLOC_ZERO (sc_hash_array_data_t, 1);
   hash_array = &had->the_hash_array;
+  hash_array->user_data = user_data;
   hash_array->internal_data = had;
 
   /* initialize all members */
@@ -1582,8 +1584,6 @@ sc_hash_array_new (size_t elem_size, sc_hash_function_t hash_fn,
   had->pa = &hash_array->a;
   had->hash_fn = hash_fn;
   had->equal_fn = equal_fn;
-  had->user_data = user_data;
-  had->current_item = NULL;
   hash_array->h = sc_hash_new (sc_hash_array_hash_fn, sc_hash_array_equal_fn,
                                had, NULL);
 
@@ -1607,6 +1607,12 @@ sc_hash_array_is_valid (sc_hash_array_t * hash_array)
   size_t              zz, position;
   void               *v;
 
+  SC_ASSERT (hash_array != NULL);
+
+  if (hash_array->a.elem_count != hash_array->h->elem_count) {
+    return 0;
+  }
+
   for (zz = 0; zz < hash_array->a.elem_count; ++zz) {
     v = sc_array_index (&hash_array->a, zz);
     found = sc_hash_array_lookup (hash_array, v, &position);
@@ -1631,6 +1637,12 @@ sc_hash_array_lookup (sc_hash_array_t * hash_array, void *v, size_t *position)
   int                 found;
   void              **found_void;
 
+  /* verify general invariant */
+  SC_ASSERT (hash_array != NULL);
+  SC_ASSERT (hash_array->a.elem_count == hash_array->h->elem_count);
+  SC_ASSERT (hash_array->internal_data->foreach_fn == NULL);
+  SC_ASSERT (hash_array->internal_data->current_item == NULL);
+
   hash_array->internal_data->current_item = v;
   found = sc_hash_lookup (hash_array->h, (void *) (-1L), &found_void);
   hash_array->internal_data->current_item = NULL;
@@ -1653,7 +1665,11 @@ sc_hash_array_insert_unique (sc_hash_array_t * hash_array, void *v,
   int                 added;
   void              **found_void;
 
+  /* verify general invariant */
+  SC_ASSERT (hash_array != NULL);
   SC_ASSERT (hash_array->a.elem_count == hash_array->h->elem_count);
+  SC_ASSERT (hash_array->internal_data->foreach_fn == NULL);
+  SC_ASSERT (hash_array->internal_data->current_item == NULL);
 
   hash_array->internal_data->current_item = v;
   added = sc_hash_insert_unique (hash_array->h, (void *) (-1L), &found_void);
@@ -1674,6 +1690,37 @@ sc_hash_array_insert_unique (sc_hash_array_t * hash_array, void *v,
   }
 }
 
+static int
+sc_hash_array_foreach_fn (void **v, const void *u)
+{
+  const sc_hash_array_data_t *internal_data =
+    (const sc_hash_array_data_t *) u;
+
+  SC_ASSERT (internal_data != NULL);
+  SC_ASSERT (internal_data->foreach_fn != NULL);
+
+  return internal_data->foreach_fn
+    (v, internal_data->the_hash_array.user_data);
+}
+
+void
+sc_hash_array_foreach (sc_hash_array_t * hash_array, sc_hash_foreach_t fn)
+{
+  /* verify general invariant */
+  SC_ASSERT (hash_array != NULL);
+  SC_ASSERT (hash_array->a.elem_count == hash_array->h->elem_count);
+  SC_ASSERT (hash_array->internal_data->foreach_fn == NULL);
+  SC_ASSERT (hash_array->internal_data->current_item == NULL);
+
+  /* verify remaining input arguments */
+  SC_ASSERT (fn != NULL);
+
+  /* rely on internal hash table's foreach function */
+  hash_array->internal_data->foreach_fn = fn;
+  sc_hash_foreach (hash_array->h, sc_hash_array_foreach_fn);
+  hash_array->internal_data->foreach_fn = NULL;
+}
+
 void
 sc_hash_array_rip (sc_hash_array_t * hash_array, sc_array_t * rip)
 {
diff --git a/src/sc_containers.h b/src/sc_containers.h
index 1998561f..4fbc375a 100644
--- a/src/sc_containers.h
+++ b/src/sc_containers.h
@@ -98,7 +98,7 @@ typedef unsigned int (*sc_hash_function_t) (const void *v, const void *u);
 typedef int         (*sc_equal_function_t) (const void *v1,
                                             const void *v2, const void *u);
 
-/** Function to call on every data item of a hash table.
+/** Function to call on every data item of a hash table or hash array.
  * \param [in] v   The address of the pointer to the current object.
  * \param [in] u   Arbitrary user data.
  * \return Return true if the traversal should continue, false to stop.
@@ -940,10 +940,10 @@ typedef struct sc_hash
 {
   /* interface variables */
   size_t              elem_count;       /**< total number of objects contained */
+  void               *user_data;        /**< User data passed to hash function. */
 
   /* implementation variables */
   sc_array_t         *slots;    /**< The slot count is slots->elem_count. */
-  void               *user_data;        /**< User data passed to hash function. */
   sc_hash_function_t  hash_fn;  /**< Function called to compute the hash value. */
   sc_equal_function_t equal_fn; /**< Function called to check objects for equality. */
   size_t              resize_checks;    /**< Running count of resize checks. */
@@ -1067,6 +1067,9 @@ typedef struct sc_hash_array_data sc_hash_array_data_t;
  */
 typedef struct sc_hash_array
 {
+  /* interface variables */
+  void               *user_data;        /**< Context passed by the user. */
+
   /* implementation variables */
   sc_array_t          a;        /**< Array storing the elements. */
   sc_hash_t          *h;        /**< Hash map pointing into element array. */
@@ -1134,6 +1137,13 @@ int                 sc_hash_array_lookup (sc_hash_array_t * hash_array,
 void               *sc_hash_array_insert_unique (sc_hash_array_t * hash_array,
                                                  void *v, size_t *position);
 
+/** Invoke a callback for every member of the hash array.
+ * \param [in,out] hash_array   Valid hash array.
+ * \param [in] fn               Callback executed on every hash array element.
+ */
+void                sc_hash_array_foreach (sc_hash_array_t * hash_array,
+                                           sc_hash_foreach_t fn);
+
 /** Extract the array data from a hash array and destroy everything else.
  * \param [in] hash_array   The hash array is destroyed after extraction.
  * \param [in] rip          Array structure that will be overwritten.
diff --git a/src/sc_io.c b/src/sc_io.c
index 86c30549..02b2f499 100644
--- a/src/sc_io.c
+++ b/src/sc_io.c
@@ -1643,6 +1643,7 @@ sc_io_open (sc_MPI_Comm mpicomm, const char *filename,
 
   return errcode;
 #else
+  /* WARNING: This code with activated MPI (SC_ENABLE_MPI) is deprecated. */
   /* allocate internal file context */
   *mpifile = (sc_MPI_File) SC_ALLOC (struct sc_no_mpiio_file, 1);
   (*mpifile)->filename = filename;
@@ -1705,16 +1706,6 @@ sc_io_read (sc_MPI_File mpifile, void *ptr, size_t zcount,
 #endif
 }
 
-int
-sc_io_read_at_legal (void)
-{
-#ifdef SC_ENABLE_MPIIO
-  return 1;
-#else
-  return 0;
-#endif
-}
-
 int
 sc_io_read_at (sc_MPI_File mpifile, sc_MPI_Offset offset, void *ptr,
                int count, sc_MPI_Datatype t, int *ocount)
@@ -1743,6 +1734,8 @@ sc_io_read_at (sc_MPI_File mpifile, sc_MPI_Offset offset, void *ptr,
   return errcode;
 #else
 
+  /* WARNING: This code with activated MPI (SC_ENABLE_MPI) is deprecated. */
+
   /* The value count > 0 is only legal on rank 0.
    * On all other ranks the code is only legal for count == 0.
    */
@@ -1826,6 +1819,9 @@ sc_io_read_at_all (sc_MPI_File mpifile, sc_MPI_Offset offset, void *ptr,
   return errcode;
 #elif defined SC_ENABLE_MPI
   /* MPI but no MPI IO */
+
+  /* WARNING: This code and configuration case is deprecated. */
+
   {
     int                 mpisize, rank, count, size;
     int                 active, errval;
@@ -1968,13 +1964,6 @@ sc_io_read_at_all (sc_MPI_File mpifile, sc_MPI_Offset offset, void *ptr,
 #endif
 }
 
-int
-sc_io_read_all (sc_MPI_File mpifile, void *ptr, int count, sc_MPI_Datatype t,
-                int *ocount)
-{
-  return sc_io_read_at_all (mpifile, 0, ptr, count, t, ocount);
-}
-
 void
 sc_io_write (sc_MPI_File mpifile, const void *ptr, size_t zcount,
              sc_MPI_Datatype t, const char *errmsg)
@@ -2001,12 +1990,6 @@ sc_io_write (sc_MPI_File mpifile, const void *ptr, size_t zcount,
 #endif
 }
 
-int
-sc_io_write_at_legal (void)
-{
-  return sc_io_read_at_legal ();
-}
-
 int
 sc_io_write_at (sc_MPI_File mpifile, sc_MPI_Offset offset,
                 const void *ptr, int count, sc_MPI_Datatype t,
@@ -2036,6 +2019,8 @@ sc_io_write_at (sc_MPI_File mpifile, sc_MPI_Offset offset,
   return errcode;
 #else
 
+  /* WARNING: This code with activated MPI (SC_ENABLE_MPI) is deprecated. */
+
   /* The value count > 0 is only legal on rank 0.
    * On all other ranks the code is only legal for count == 0.
    */
@@ -2119,6 +2104,9 @@ sc_io_write_at_all (sc_MPI_File mpifile, sc_MPI_Offset offset,
   return errcode;
 #elif defined SC_ENABLE_MPI
   /* MPI but no MPI IO */
+
+  /* WARNING: This code and configuration case is deprecated. */
+
   /* offset is ignored and we use here the append mode.
    * This is the case since the C-standard open mode
    * "wb" would earse the existing file and create a
@@ -2265,13 +2253,6 @@ sc_io_write_at_all (sc_MPI_File mpifile, sc_MPI_Offset offset,
 #endif
 }
 
-int
-sc_io_write_all (sc_MPI_File mpifile, const void *ptr, int count,
-                 sc_MPI_Datatype t, int *ocount)
-{
-  return sc_io_write_at_all (mpifile, 0, ptr, count, t, ocount);
-}
-
 int
 sc_io_close (sc_MPI_File * mpifile)
 {
@@ -2285,6 +2266,9 @@ sc_io_close (sc_MPI_File * mpifile)
   mpiret = sc_io_error_class (mpiret, &eclass);
   SC_CHECK_MPI (mpiret);
 #else
+
+  /* WARNING: This code with activated MPI (SC_ENABLE_MPI) is deprecated. */
+
   int                 retval;
 
   eclass = sc_MPI_SUCCESS;
diff --git a/src/sc_io.h b/src/sc_io.h
index 3c84389b..4e22232b 100644
--- a/src/sc_io.h
+++ b/src/sc_io.h
@@ -32,7 +32,7 @@
  *    provide functions centered around \ref sc_io_sink_new and \ref
  *    sc_io_source_new.
  *  - To abstract parallel file I/O in a way that works both with and
- *    without MPI I/O support, we provide \ref sc_io_open, \ref sc_io_write
+ *    without MPI support, we provide \ref sc_io_open, \ref sc_io_write
  *    and friends.
  *  - To write to the VTK binary compressed format, we provide suitable
  *    functions to base64 encode and zlib-compress as required; see
@@ -44,22 +44,6 @@
  *    and base64-encoded format and back that is unambiguously defined and
  *    human-friendly.
  *
- * \note For the function \ref sc_io_write_at_all without MPI IO but with MPI
- *       the \b offset argument is ignored. In this case the function writes at
- *       the current end of the file. Hereby, the MPI ranks write in the
- *       rank-induced order. That is why the function may work equivalent to
- *       the MPI IO and non-MPI case but it can not be guaranteed.
- *       Furthermore, it is important to notice that \ref sc_io_write_at and
- *       \ref sc_io_read_at are only valid to call with zcount > 0 on rank 0,
- *       if MPI IO is not available. During runtime this can be checked by the
- *       user by calling \ref sc_io_read_at_legal and \ref sc_io_write_at_legal,
- *       respectively.
- *       The recommended way of reading/writing with multiple ranks with
- *       zcount > 0 if \ref sc_io_read_at_legal / \ref sc_io_write_at_legal
- *       returns 0 is to use \ref sc_io_read_at_all / \ref sc_io_write_at_all
- *       with the whished zcount on the ranks whished by the user and set zcount
- *       to 0 on the remaining ranks. 
- *
  * \ingroup io
  */
 
@@ -582,14 +566,15 @@ void                sc_fread (void *ptr, size_t size,
  */
 void                sc_fflush_fsync_fclose (FILE * file);
 
-/** Opens a MPI file or without MPI I/O or even without MPI a file context.
+/** Opens a MPI file or without MPI a file context.
+ *
  * \param[in] mpicomm   MPI communicator
  * \param[in] filename  The path to the file that we want to open.
  * \param[in] amode     An access mode.
  * \param[in] mpiinfo   The MPI info
  * \param[out] mpifile  The MPI file that is opened. This can be a
  *                      an actual MPI IO file or an internal file
- *                      conntext to preserve some MPI IO functionalities
+ *                      conntext to preserve some IO functionalities
  *                      without MPI IO and to have working code without
  *                      MPI at all. This output variable is only filled if the
  *                      return value of the function is \ref sc_MPI_SUCCESS.
@@ -623,23 +608,10 @@ void                sc_io_read (sc_MPI_File mpifile, void *ptr,
                                 size_t zcount, sc_MPI_Datatype t,
                                 const char *errmsg);
 
-/** Check for restricted usage of \ref sc_io_read_at.
- *
- * \return              0 if the restriction described in the note of \ref
- *                      sc_io_read_at applies, i.e. count > 0 is only legal
- *                      on rank 0. This is equivalent to MPI I/O being not
- *                      available.
- *                      Otherwise, the function returns 1, i.e. MPI I/O is
- *                      available and the restriction in the note of \ref
- *                      sc_io_read_at does not apply, i.e. the user can pass
- *                      any valid count on any valid rank.
- *
- */
-int                 sc_io_read_at_legal (void);
-
 /** Read MPI file content into memory for an explicit offset.
  * This function does not update the file pointer of the MPI file.
  * Contrary to \ref sc_io_read, it does not abort on read errors.
+ *
  * \param [in,out] mpifile      MPI file object opened for reading.
  * \param [in] offset   Starting offset in counts of the type \b t.
  * \param [in] ptr      Data array to read from disk.
@@ -649,11 +621,6 @@ int                 sc_io_read_at_legal (void);
  * \return              A sc_MPI_ERR_* as defined in \ref sc_mpi.h.
  *                      The error code can be passed to
  *                      \ref sc_MPI_Error_string.
- * \note                If MPI I/O is not available this function has restricted
- *                      functionality in the sense that for \b count > 0, this
- *                      function is only legal to call on rank 0. On all other
- *                      ranks \b count must be 0. If this requirement is
- *                      violated this function returns \ref sc_MPI_ERR_ARG.
  */
 int                 sc_io_read_at (sc_MPI_File mpifile,
                                    sc_MPI_Offset offset, void *ptr,
@@ -662,6 +629,7 @@ int                 sc_io_read_at (sc_MPI_File mpifile,
 
 /** Read MPI file content collectively into memory for an explicit offset.
  * This function does not update the file pointer of the MPI file.
+ *
  * \param [in,out] mpifile      MPI file object opened for reading.
  * \param [in] offset   Starting offset in counts of the type \b t.
  * \param [in] ptr      Data array to read from disk.
@@ -677,24 +645,6 @@ int                 sc_io_read_at_all (sc_MPI_File mpifile,
                                        int count, sc_MPI_Datatype t,
                                        int *ocount);
 
-/** Read memory content collectively from an MPI file.
- * A call of this function is equivalent to call \ref sc_io_read_at_all
- * with offset = 0 but the call of this function is not equivalent
- * to a call of MPI_File_read_all since this function ignores the current
- * position of the file cursor.
- * \param [in,out] mpifile      MPI file object opened for reading.
- * \param [in] ptr      Data array to read from disk.
- * \param [in] count    Number of array members.
- * \param [in] t        The MPI type for each array member.
- * \param [out] ocount  The number of read elements of type \b t.
- * \return              A sc_MPI_ERR_* as defined in \ref sc_mpi.h.
- *                      The error code can be passed to
- *                      \ref sc_MPI_Error_string.
- */
-int                 sc_io_read_all (sc_MPI_File mpifile, void *ptr,
-                                    int count, sc_MPI_Datatype t,
-                                    int *ocount);
-
 #define sc_mpi_write        sc_io_write  /**< For backwards compatibility. */
 
 /** Write memory content to an MPI file.
@@ -713,23 +663,10 @@ void                sc_io_write (sc_MPI_File mpifile, const void *ptr,
                                  size_t zcount, sc_MPI_Datatype t,
                                  const char *errmsg);
 
-/** Check for restricted usage of \ref sc_io_write_at.
- *
- * \return              0 if the restriction described in the note of \ref
- *                      sc_io_write_at applies, i.e. count > 0 is only legal
- *                      on rank 0. This is equivalent to MPI I/O being not
- *                      available.
- *                      Otherwise, the function returns 1, i.e. MPI I/O is
- *                      available and the restriction in the note of \ref
- *                      sc_io_write_at does not apply, i.e. the user can pass
- *                      any valid count on any valid rank.
- *
- */
-int                 sc_io_write_at_legal (void);
-
 /** Write MPI file content into memory for an explicit offset.
  * This function does not update the file pointer that is part of mpifile.
- * Contrary to \ref sc_io_write, it does not abort on read errors. 
+ * Contrary to \ref sc_io_write, it does not abort on read errors.
+ *
  * \param [in,out] mpifile      MPI file object opened for reading.
  * \param [in] offset   Starting offset in etype, where the etype is given by
  *                      the type t.
@@ -740,11 +677,6 @@ int                 sc_io_write_at_legal (void);
  * \return              A sc_MPI_ERR_* as defined in \ref sc_mpi.h.
  *                      The error code can be passed to
  *                      \ref sc_MPI_Error_string.
- * \note                If MPI I/O is not available this function has restricted
- *                      functionality in the sense that for \b count > 0, this
- *                      function is only legal to call on rank 0. On all other
- *                      ranks \b count must be 0. If this requirement is
- *                      violated this function returns \ref sc_MPI_ERR_ARG.
  */
 int                 sc_io_write_at (sc_MPI_File mpifile,
                                     sc_MPI_Offset offset,
@@ -754,15 +686,9 @@ int                 sc_io_write_at (sc_MPI_File mpifile,
 /** Write MPI file content collectively into memory for an explicit offset.
  * This function does not update the file pointer that is part of mpifile.
  *
- * \note  If there is no MPI IO but MPI available, the offset parameter is
- *        ignored and the ranks just write at the current end of the file
- *        according to their rank-induced order.
  * \param [in,out] mpifile      MPI file object opened for reading.
  * \param [in] offset   Starting offset in etype, where the etype is given by
- *                      the type t. This parameter is ignored in the case of
- *                      having MPI but no MPI IO. In this case this function
- *                      writes to the current end of the file as described
- *                      above.
+ *                      the type t.
  * \param [in] ptr      Data array to write to disk.
  * \param [in] count    Number of array members.
  * \param [in] t        The MPI type for each array member.
@@ -776,25 +702,8 @@ int                 sc_io_write_at_all (sc_MPI_File mpifile,
                                         const void *ptr, int count,
                                         sc_MPI_Datatype t, int *ocount);
 
-/** Write memory content collectively to an MPI file.
- * A call of this function is equivalent to call \ref sc_io_write_at_all
- * with offset = 0 but the call of this function is not equivalent
- * to a call of MPI_File_write_all since this function ignores the current
- * position of the file cursor.
- * \param [in,out] mpifile      MPI file object opened for writing.
- * \param [in] ptr      Data array to write to disk.
- * \param [in] count    Number of array members.
- * \param [in] t        The MPI type for each array member.
- * \param [out] ocount  The number of written elements of type \b t.
- * \return              A sc_MPI_ERR_* as defined in \ref sc_mpi.h.
- *                      The error code can be passed to
- *                      \ref sc_MPI_Error_string.
- */
-int                 sc_io_write_all (sc_MPI_File mpifile,
-                                     const void *ptr, int count,
-                                     sc_MPI_Datatype t, int *ocount);
-
 /** Close collectively a sc_MPI_File.
+ *
  * \param[in] file  MPI file object that is closed.
  * \return              A sc_MPI_ERR_* as defined in \ref sc_mpi.h.
  *                      The error code can be passed to
diff --git a/src/sc_mpi.c b/src/sc_mpi.c
index ce11ae96..6dfa04fc 100644
--- a/src/sc_mpi.c
+++ b/src/sc_mpi.c
@@ -450,6 +450,73 @@ sc_MPI_Wtime (void)
   return (double) tv.tv_sec + 1.e-6 * tv.tv_usec;
 }
 
+int
+sc_MPI_Pack (const void *inbuf, int incount, sc_MPI_Datatype datatype,
+             void *outbuf, int outsize, int *position, sc_MPI_Comm comm)
+{
+  int                 mpiret;
+  int                 size;
+
+  SC_ASSERT (incount >= 0);
+  SC_ASSERT (position != NULL);
+
+  mpiret = sc_MPI_Pack_size (incount, datatype, comm, &size);
+  SC_CHECK_MPI (mpiret);
+
+  /* Check that we have enough space to pack the datatypes */
+  if (*position + size > outsize) {
+    return sc_MPI_ERR_NO_SPACE;
+  }
+
+  /* Copy the contiguous memory */
+  memcpy ((char *) outbuf + *position, inbuf, size);
+  *position += size;
+
+  return sc_MPI_SUCCESS;
+}
+
+int
+sc_MPI_Unpack (const void *inbuf, int insize, int *position,
+               void *outbuf, int outcount, sc_MPI_Datatype datatype,
+               sc_MPI_Comm comm)
+{
+  int                 mpiret;
+  int                 size;
+
+  SC_ASSERT (position != NULL);
+  SC_ASSERT (outcount >= 0);
+
+  mpiret = sc_MPI_Pack_size (outcount, datatype, comm, &size);
+  SC_CHECK_MPI (mpiret);
+
+  /* Check that the message is big enough for the datatypes that we want */
+  if (*position + size > insize) {
+    return sc_MPI_ERR_NO_SPACE;
+  }
+
+  /* Copy the contiguous memory */
+  memcpy (outbuf, (char *) inbuf + *position, size);
+  *position += size;
+
+  return sc_MPI_SUCCESS;
+}
+
+int
+sc_MPI_Pack_size (int incount, sc_MPI_Datatype datatype, sc_MPI_Comm comm,
+                  int *size)
+{
+  int                 mpiret;
+
+  SC_ASSERT (incount >= 0);
+  SC_ASSERT (size != NULL);
+
+  mpiret = sc_MPI_Type_size (datatype, size);
+  SC_CHECK_MPI (mpiret);
+  *size *= incount;
+
+  return sc_MPI_SUCCESS;
+}
+
 #else /* SC_ENABLE_MPI */
 #ifndef SC_ENABLE_MPITHREAD
 
@@ -680,10 +747,10 @@ sc_MPI_Error_string (int errorcode, char *string, int *resultlen)
 size_t
 sc_mpi_sizeof (sc_MPI_Datatype t)
 {
-  if (t == sc_MPI_CHAR)
-    return sizeof (char);
   if (t == sc_MPI_BYTE)
     return 1;
+  if (t == sc_MPI_CHAR || t == sc_MPI_UNSIGNED_CHAR)
+    return sizeof (char);
   if (t == sc_MPI_SHORT || t == sc_MPI_UNSIGNED_SHORT)
     return sizeof (short);
   if (t == sc_MPI_INT || t == sc_MPI_UNSIGNED)
@@ -692,8 +759,6 @@ sc_mpi_sizeof (sc_MPI_Datatype t)
     return sizeof (long);
   if (t == sc_MPI_LONG_LONG_INT)
     return sizeof (long long);
-  if (t == sc_MPI_UNSIGNED_LONG_LONG)
-    return sizeof (unsigned long long);
   if (t == sc_MPI_FLOAT)
     return sizeof (float);
   if (t == sc_MPI_DOUBLE)
@@ -702,6 +767,8 @@ sc_mpi_sizeof (sc_MPI_Datatype t)
     return sizeof (long double);
   if (t == sc_MPI_2INT)
     return 2 * sizeof (int);
+  if (t == sc_MPI_DOUBLE_INT)
+    return sizeof (double) + sizeof (int);
 
   SC_ABORT_NOT_REACHED ();
 }
diff --git a/src/sc_mpi.h b/src/sc_mpi.h
index b74fa0ea..70b74ef3 100644
--- a/src/sc_mpi.h
+++ b/src/sc_mpi.h
@@ -107,6 +107,7 @@ sc_tag_t;
 /* constants */
 #define sc_MPI_SUCCESS             MPI_SUCCESS
 #define sc_MPI_ERR_ARG             MPI_ERR_ARG
+#define sc_MPI_ERR_COUNT           MPI_ERR_COUNT
 #define sc_MPI_ERR_UNKNOWN         MPI_ERR_UNKNOWN
 #define sc_MPI_ERR_OTHER           MPI_ERR_OTHER
 #define sc_MPI_ERR_NO_MEM          MPI_ERR_NO_MEM
@@ -138,6 +139,9 @@ sc_tag_t;
 typedef enum sc_MPI_IO_Errorcode
 {
   /* only MPI I/O error classes */
+  /* WARNING: This enum is only used in the deprecated case of activated MPI but
+   * deactivated MPI I/O.
+   */
   sc_MPI_ERR_FILE = MPI_ERR_LASTCODE,
   sc_MPI_ERR_NOT_SAME,
   sc_MPI_ERR_AMODE,
@@ -153,7 +157,6 @@ typedef enum sc_MPI_IO_Errorcode
   sc_MPI_ERR_FILE_IN_USE,
   sc_MPI_ERR_DUP_DATAREP,
   sc_MPI_ERR_CONVERSION,
-  sc_MPI_ERR_COUNT,
   sc_MPI_ERR_IO,
   sc_MPI_ERR_LASTCODE
 }
@@ -182,22 +185,22 @@ sc_MPI_IO_Errorcode_t;
 #define sc_MPI_REQUEST_NULL        MPI_REQUEST_NULL
 
 #define sc_MPI_DATATYPE_NULL       MPI_DATATYPE_NULL
+#define sc_MPI_BYTE                MPI_BYTE
 #define sc_MPI_CHAR                MPI_CHAR
-#define sc_MPI_SIGNED_CHAR         MPI_SIGNED_CHAR
 #define sc_MPI_UNSIGNED_CHAR       MPI_UNSIGNED_CHAR
-#define sc_MPI_BYTE                MPI_BYTE
 #define sc_MPI_SHORT               MPI_SHORT
 #define sc_MPI_UNSIGNED_SHORT      MPI_UNSIGNED_SHORT
 #define sc_MPI_INT                 MPI_INT
-#define sc_MPI_2INT                MPI_2INT
 #define sc_MPI_UNSIGNED            MPI_UNSIGNED
 #define sc_MPI_LONG                MPI_LONG
 #define sc_MPI_UNSIGNED_LONG       MPI_UNSIGNED_LONG
 #define sc_MPI_LONG_LONG_INT       MPI_LONG_LONG_INT
-#define sc_MPI_UNSIGNED_LONG_LONG  MPI_UNSIGNED_LONG_LONG
 #define sc_MPI_FLOAT               MPI_FLOAT
 #define sc_MPI_DOUBLE              MPI_DOUBLE
 #define sc_MPI_LONG_DOUBLE         MPI_LONG_DOUBLE
+#define sc_MPI_2INT                MPI_2INT
+#define sc_MPI_DOUBLE_INT          MPI_DOUBLE_INT
+#define sc_MPI_PACKED              MPI_PACKED
 
 #define sc_MPI_OP_NULL             MPI_OP_NULL
 #define sc_MPI_MAX                 MPI_MAX
@@ -288,6 +291,9 @@ sc_MPI_IO_Errorcode_t;
 #define sc_MPI_Wait                MPI_Wait
 /* The MPI_Waitsome, MPI_Waitall and MPI_Testall functions are wrapped. */
 #define sc_MPI_Type_size           MPI_Type_size
+#define sc_MPI_Pack                MPI_Pack
+#define sc_MPI_Unpack              MPI_Unpack
+#define sc_MPI_Pack_size           MPI_Pack_size
 
 #else /* !SC_ENABLE_MPI */
 #include <sc3_mpi_types.h>
@@ -296,6 +302,7 @@ sc_MPI_IO_Errorcode_t;
 
 #define sc_MPI_SUCCESS          SC3_MPI_SUCCESS         /**< Emulate \c SC_MPI_SUCCESS. */
 #define sc_MPI_ERR_ARG          SC3_MPI_ERR_ARG         /**< Emulate \c SC_MPI_ERR_ARG. */
+#define sc_MPI_ERR_COUNT        SC3_MPI_ERR_COUNT       /**< Emulate \c SC_MPI_ERR_COUNT. */
 #define sc_MPI_ERR_UNKNOWN      SC3_MPI_ERR_UNKNOWN     /**< Emulate \c SC_MPI_ERR_UNKNOWN. */
 #define sc_MPI_ERR_OTHER        SC3_MPI_ERR_OTHER       /**< Emulate \c SC_MPI_ERR_OTHER. */
 #define sc_MPI_ERR_NO_MEM       SC3_MPI_ERR_NO_MEM      /**< Emulate \c SC_MPI_ERR_NO_MEM. */
@@ -347,7 +354,6 @@ sc_MPI_IO_Errorcode_t;
 #define sc_MPI_DATATYPE_NULL       SC3_MPI_DATATYPE_NULL
 
 #define sc_MPI_CHAR                ((sc_MPI_Datatype) 0x4c000101)
-#define sc_MPI_SIGNED_CHAR         ((sc_MPI_Datatype) 0x4c000118)
 #define sc_MPI_UNSIGNED_CHAR       ((sc_MPI_Datatype) 0x4c000102)
 #define sc_MPI_BYTE                SC3_MPI_BYTE
 #define sc_MPI_SHORT               ((sc_MPI_Datatype) 0x4c000203)
@@ -358,11 +364,11 @@ sc_MPI_IO_Errorcode_t;
 #define sc_MPI_LONG                SC3_MPI_LONG
 #define sc_MPI_UNSIGNED_LONG       ((sc_MPI_Datatype) 0x4c000408)
 #define sc_MPI_LONG_LONG_INT       SC3_MPI_LONG_LONG
-#define sc_MPI_UNSIGNED_LONG_LONG  ((sc_MPI_Datatype) 0x4c000409)
 #define sc_MPI_FLOAT               SC3_MPI_FLOAT
 #define sc_MPI_DOUBLE              SC3_MPI_DOUBLE
 #define sc_MPI_DOUBLE_INT          SC3_MPI_DOUBLE_INT
 #define sc_MPI_LONG_DOUBLE         ((sc_MPI_Datatype) 0x4c000c0c)
+#define sc_MPI_PACKED              ((sc_MPI_Datatype) 0x4c001001)
 
 #define sc_MPI_OP_NULL             SC3_MPI_OP_NULL
 #define sc_MPI_MINLOC              SC3_MPI_MINLOC
@@ -445,6 +451,47 @@ int                 sc_MPI_Comm_free (sc_MPI_Comm *freecomm);
  */
 int                 sc_MPI_Type_size (sc_MPI_Datatype datatype, int *size);
 
+/** Pack several instances of the same datatype into contiguous memory.
+ * \param [in] inbuf          Buffer of elements of type \b datatype.
+ * \param [in] incount        Number of elements in \b inbuf.
+ * \param [in] datatype       Datatype of elements in \b inbuf.
+ * \param [out] outbuf        Output buffer in which elements are packed.
+ * \param [in] outsize        Size of output buffer in bytes.
+ * \param [in, out] position  The current position in the output buffer.
+ * \param [in] comm           Valid MPI communicator.
+ * \return                    MPI_SUCCESS on success.
+ */
+int                 sc_MPI_Pack (const void *inbuf, int incount,
+                                 sc_MPI_Datatype datatype, void *outbuf,
+                                 int outsize, int *position,
+                                 sc_MPI_Comm comm);
+
+/** Unpack contiguous memory into several instances of the same datatype.
+ * \param [in] inbuf          Buffer of packed data.
+ * \param [in] insize         Number of bytes in \b inbuf
+ * \param [in, out] position  The current position in the input buffer.
+ * \param [out] outbuf        Output buffer in which elements are unpacked.
+ * \param [in] outcount       Number of elements to unpack.
+ * \param [in] datatype       Datatype of elements to be unpacked.
+ * \param [in] comm           Valid MPI communicator.
+ * \return                    MPI_SUCCESS on success.
+ */
+int                 sc_MPI_Unpack (const void *inbuf, int insize,
+                                   int *position, void *outbuf, int outcount,
+                                   sc_MPI_Datatype datatype,
+                                   sc_MPI_Comm comm);
+
+/** Determine space needed to pack several instances of the same datatype.
+ * \param [in] incount        Number of elements to pack.
+ * \param [in] datatype       Datatype of elements to pack.
+ * \param [in] comm           Valid MPI communicator.
+ * \param [out] size          Number of bytes needed to packed \b incount
+ *                            instances of \b datatype.
+ * \return                    MPI_SUCCESS on success.
+ */
+int                 sc_MPI_Pack_size (int incount, sc_MPI_Datatype datatype,
+                                      sc_MPI_Comm comm, int *size);
+
 /** Query size of an MPI communicator.
  * \param [in] mpicomm      Valid MPI communicator.
  * \param [out] mpisize     Without MPI this is always 1.
@@ -694,8 +741,8 @@ int                 sc_MPI_Error_class (int errorcode, int *errorclass);
 int                 sc_MPI_Error_string (int errorcode, char *string,
                                          int *resultlen);
 
-/** Return the size of MPI data types.
- * \param [in] t    MPI data type.
+/** Return the size of MPI datatypes.
+ * \param [in] t    MPI datatype.
  * \return          Returns the size in bytes.
  */
 size_t              sc_mpi_sizeof (sc_MPI_Datatype t);
diff --git a/src/sc_scda.h b/src/sc_scda.h
index 83404f1d..eaa63ae3 100644
--- a/src/sc_scda.h
+++ b/src/sc_scda.h
@@ -135,10 +135,10 @@
  * - \ref sc_scda_ferror_class and
  * - \ref sc_scda_ferror_string.
  *
- * If MPI I/O is available \b errcode may encode an MPI error code. In this case
+ * If MPI is available \b errcode may encode an MPI error code. In this case
  * the two error examination functions output the error class and error string
  * as it would be output by the corresponding MPI functions, respectively.
- * Without MPI I/O or MPI it is still possible that \b errcode encodes an I/O
+ * Without MPI it is still possible that \b errcode encodes an I/O
  * operation related error code. This case does not differ concerning the error
  * code examiniation.
  * Moreover, \b errcode can encode an error code related to \b scda, i.e.
@@ -214,7 +214,7 @@ typedef uint64_t    sc_scda_ulong;
 typedef enum sc_scda_ret
 {
   SC_SCDA_FERR_SUCCESS = 0, /**< successful function call */
-  SC_SCDA_FERR_FORMAT = sc_MPI_ERR_LASTCODE,  /**< File not conforming to the
+  SC_SCDA_FERR_FORMAT = 15000, /**< File not conforming to the
                                                    \b scda format. */
   SC_SCDA_FERR_USAGE,   /**< Incorrect workflow of an \b scda reading function.
                              For example, the user might have identified a
@@ -264,7 +264,7 @@ sc_scda_ret_t;
  */
 typedef struct sc_scda_ferror
 {
-  int mpiret;            /**< MPI function return value; without MPI I/O or MPI
+  int mpiret;            /**< MPI function return value; without MPI
                               this variable can get filled by other I/O operation
                               error codes, which are still interpretable by
                               the error \b scda examination functions */
@@ -287,8 +287,8 @@ sc_scda_fopen_options_t; /**< type for \ref sc_scda_fopen_options */
  * It is collective and creates the file on a parallel file system.
  * \note
  * All parameters are collective.
- * This function leaves the file open if MPI I/O is available.
- * Independent of the availability of MPI I/O the user can write one or more
+ * This function leaves the file open if MPI is available.
+ * Independent of the availability of MPI the user can write one or more
  * file sections before closing the file (context) using \ref sc_scda_fclose.
  *
  * It is the user's responsibility to write any further
@@ -303,8 +303,7 @@ sc_scda_fopen_options_t; /**< type for \ref sc_scda_fopen_options */
  * introduced in this \b scda
  * [preprint](https://doi.org/10.48550/arXiv.2307.06789).
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in]     mpicomm   The MPI communicator that is used to open the
  *                           parallel file.
@@ -347,9 +346,7 @@ sc_scda_fcontext_t *sc_scda_fopen_write (sc_MPI_Comm mpicomm,
  * \note
  * All parameters except of \b data are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_write.
@@ -393,9 +390,7 @@ sc_scda_fcontext_t *sc_scda_fwrite_inline (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b block_data are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_write.
@@ -455,9 +450,7 @@ sc_scda_fcontext_t *sc_scda_fwrite_block (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b array_data are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_write.
@@ -568,9 +561,7 @@ int                 sc_scda_proc_sizes (sc_array_t * elem_sizes,
  * \note
  * All parameters except of \b array_data and \b elem_sizes are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_write.
@@ -672,8 +663,7 @@ sc_scda_fcontext_t *sc_scda_fwrite_varray (sc_scda_fcontext_t * fc,
  * introduced in this \b scda
  * [preprint](https://doi.org/10.48550/arXiv.2307.06789).
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in]     mpicomm   The MPI communicator that is used to open the
  *                           parallel file.
@@ -715,9 +705,7 @@ sc_scda_fcontext_t *sc_scda_fopen_read (sc_MPI_Comm mpicomm,
  * \note
  * All parameters are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -784,9 +772,7 @@ sc_scda_fcontext_t *sc_scda_fread_section_header (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b data are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -820,9 +806,7 @@ sc_scda_fcontext_t *sc_scda_fread_inline_data (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b data_block are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -862,9 +846,7 @@ sc_scda_fcontext_t *sc_scda_fread_block_data (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b array_data are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -926,9 +908,7 @@ sc_scda_fcontext_t *sc_scda_fread_array_data (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b elem_sizes are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -975,9 +955,7 @@ sc_scda_fcontext_t *sc_scda_fread_varray_sizes (sc_scda_fcontext_t * fc,
  * \note
  * All parameters except of \b array_data and \b elem_sizes are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc          File context previously opened by \ref
  *                              sc_scda_fopen_read.
@@ -1091,9 +1069,7 @@ int                 sc_scda_ferror_string (sc_scda_ferror_t errcode, char *str,
  * \note
  * All parameters are collective.
  *
- * This function returns NULL on MPI I/O errors.
- * Without MPI I/O the function may abort on file system dependent
- * errors.
+ * This function returns NULL on I/O errors.
  *
  * \param [in,out]  fc        File context previously created by
  *                            \ref sc_scda_fopen_write or \ref
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8139d804..97cec0e7 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,3 +1,5 @@
+include(CTest)
+
 set(sc_tests allgather arrays keyvalue notify reduce search sortb version)
 
 if(SC_HAVE_RANDOM AND SC_HAVE_SRANDOM)
diff --git a/test/Makefile.am b/test/Makefile.am
index 47d6bd29..0ae79a29 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -18,6 +18,7 @@ sc_test_programs = \
         test/sc_test_sortb \
         test/sc_test_version \
         test/sc_test_helpers \
+        test/sc_test_mpi_pack \
         test/sc_test_scda
 
 ## Reenable and properly verify pqueue when it is actually used
@@ -41,6 +42,7 @@ test_sc_test_sort_SOURCES = test/test_sort.c
 test_sc_test_sortb_SOURCES = test/test_sortb.c
 test_sc_test_version_SOURCES = test/test_version.c
 test_sc_test_helpers_SOURCES = test/test_helpers.c
+test_sc_test_mpi_pack_SOURCES = test/test_mpi_pack.c
 test_sc_test_scda_SOURCES = test/test_scda.c
 
 TESTS += $(sc_test_programs)
diff --git a/test/test_mpi_pack.c b/test/test_mpi_pack.c
new file mode 100644
index 00000000..a54b9410
--- /dev/null
+++ b/test/test_mpi_pack.c
@@ -0,0 +1,226 @@
+/*
+  This file is part of the SC Library.
+  The SC Library provides support for parallel scientific applications.
+
+  Copyright (C) 2020 individual authors
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+  1. Redistributions of source code must retain the above copyright notice,
+  this list of conditions and the following disclaimer.
+
+  2. Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+  POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <sc.h>
+#include <sc_mpi.h>
+
+/** Test the mpi pack and unpack function
+ * Construct multiple test messages, each with different size double arrays depending on their type
+ * Pack, Unpack and Compare
+*/
+
+#define TEST_NUM_TYPES 3
+const int           num_values[TEST_NUM_TYPES] = { 2, 5, 6 };
+
+typedef struct message
+{
+  int8_t              type;
+  double             *values;
+}
+test_message_t;
+
+static void
+test_message_construct (test_message_t *message, int8_t type,
+                        double startvalue)
+{
+  int                 ival;
+
+  message->type = type;
+  message->values = SC_ALLOC (double, num_values[type]);
+  for (ival = 0; ival < num_values[type]; ival++) {
+    message->values[ival] = startvalue * ival;
+  }
+}
+
+static void
+test_message_destroy (test_message_t *message)
+{
+  SC_FREE (message->values);
+}
+
+static int
+test_message_equal (test_message_t *message1, test_message_t *message2)
+{
+  int                 ivalue;
+
+  if (message1->type != message2->type) {
+    return 0;
+  }
+  for (ivalue = 0; ivalue < num_values[message1->type]; ivalue++) {
+    if (message1->values[ivalue] != message2->values[ivalue]) {
+      return 0;
+    }
+  }
+  return 1;
+}
+
+/* Pack several instances of test messages into contiguous memory */
+static int
+test_message_MPI_Pack (const test_message_t *messages, int incount,
+                       void *outbuf, int outsize, int *position,
+                       sc_MPI_Comm comm)
+{
+  int                 imessage;
+
+  for (imessage = 0; imessage < incount; imessage++) {
+    int                 mpiret;
+
+    mpiret =
+      sc_MPI_Pack (&(messages[imessage].type), sizeof (int8_t), sc_MPI_BYTE,
+                   outbuf, outsize, position, comm);
+    SC_CHECK_MPI (mpiret);
+    mpiret = sc_MPI_Pack (messages[imessage].values,
+                          num_values[messages[imessage].type], sc_MPI_DOUBLE,
+                          outbuf, outsize, position, comm);
+    SC_CHECK_MPI (mpiret);
+  }
+  return 0;
+}
+
+/* Unpack contiguous memory into several instances of the same datatype */
+static int
+test_message_MPI_Unpack (const void *inbuf, int insize,
+                         int *position, test_message_t *messages,
+                         int outcount, sc_MPI_Comm comm)
+{
+  int                 imessage;
+
+  for (imessage = 0; imessage < outcount; imessage++) {
+    int                 mpiret;
+
+    mpiret =
+      sc_MPI_Unpack (inbuf, insize, position, &(messages[imessage].type),
+                     sizeof (int8_t), sc_MPI_BYTE, comm);
+    SC_CHECK_MPI (mpiret);
+
+    messages[imessage].values =
+      SC_ALLOC (double, num_values[messages[imessage].type]);
+    mpiret =
+      sc_MPI_Unpack (inbuf, insize, position, messages[imessage].values,
+                     num_values[messages[imessage].type], sc_MPI_DOUBLE,
+                     comm);
+    SC_CHECK_MPI (mpiret);
+  }
+  return 0;
+}
+
+/* Determine how much space in bytes is needed to pack several test messages */
+static int
+test_message_MPI_Pack_size (int incount, const test_message_t *messages,
+                            sc_MPI_Comm comm, int *size)
+{
+  int                 imessage;
+
+  *size = 0;
+  for (imessage = 0; imessage < incount; imessage++) {
+    int                 pack_size;
+    int                 single_message_size = 0;
+    int                 mpiret;
+
+    mpiret =
+      sc_MPI_Pack_size (sizeof (int8_t), sc_MPI_BYTE, comm, &pack_size);
+    SC_CHECK_MPI (mpiret);
+    single_message_size += pack_size;
+
+    mpiret = sc_MPI_Pack_size (1, sc_MPI_DOUBLE, comm, &pack_size);
+    SC_CHECK_MPI (mpiret);
+    single_message_size += num_values[messages[imessage].type] * pack_size;
+
+    *size += single_message_size;
+  }
+  return 0;
+}
+
+int
+main (int argc, char **argv)
+{
+  int                 mpiret;
+  sc_MPI_Comm         mpicomm;
+
+  const int           num_test_messages = 5;
+  int                 imessage;
+  test_message_t     *messages;
+  test_message_t     *unpacked_messages;
+
+  char               *pack_buffer;
+  int                 buffer_size = 0;
+  int                 position = 0;
+
+  /* standard initialization */
+  mpiret = sc_MPI_Init (&argc, &argv);
+  SC_CHECK_MPI (mpiret);
+  mpicomm = sc_MPI_COMM_WORLD;
+  sc_init (mpicomm, 1, 1, NULL, SC_LP_DEFAULT);
+
+  /* allocate and construct test messages */
+  messages = SC_ALLOC (test_message_t, num_test_messages);
+  for (imessage = 0; imessage < num_test_messages; imessage++) {
+    test_message_construct (messages + imessage, imessage % TEST_NUM_TYPES,
+                            imessage + 1.0);
+  }
+
+  /* get message size, pack, unpack and compare */
+  test_message_MPI_Pack_size (num_test_messages, messages, mpicomm,
+                              &buffer_size);
+
+  pack_buffer = SC_ALLOC (char, buffer_size);
+  test_message_MPI_Pack (messages, num_test_messages, pack_buffer,
+                         buffer_size, &position, mpicomm);
+  SC_CHECK_ABORT (position == buffer_size, "message not of full size");
+
+  unpacked_messages = SC_ALLOC (test_message_t, num_test_messages);
+  position = 0;
+  test_message_MPI_Unpack (pack_buffer, buffer_size, &position,
+                           unpacked_messages, num_test_messages, mpicomm);
+  SC_CHECK_ABORT (position == buffer_size, "message not of full size");
+
+  for (imessage = 0; imessage < num_test_messages; imessage++) {
+    SC_CHECK_ABORT (test_message_equal
+                    (messages + imessage, unpacked_messages + imessage),
+                    "message do not equal");
+  }
+
+  /* free up memory */
+  SC_FREE (pack_buffer);
+
+  for (imessage = 0; imessage < num_test_messages; imessage++) {
+    test_message_destroy (messages + imessage);
+    test_message_destroy (unpacked_messages + imessage);
+  }
+  SC_FREE (messages);
+  SC_FREE (unpacked_messages);
+
+  /* clean up and exit */
+  sc_finalize ();
+
+  mpiret = sc_MPI_Finalize ();
+  SC_CHECK_MPI (mpiret);
+
+  return EXIT_SUCCESS;
+}