diff --git a/ci/ci_lint_ci.sh b/ci/ci_lint_ci.sh
index ce3793d..fa45c54 100755
--- a/ci/ci_lint_ci.sh
+++ b/ci/ci_lint_ci.sh
@@ -60,8 +60,8 @@
 
 function main {
     [[ $# -eq 0 ]] || {
-        ci_info "note: this program accepts environment options only"
-        ci_err "unsupported command argument: '$1'"
+        ci_info "usage: $CI_SCRIPT_NAME"
+        ci_err "unexpected command argument: '$1'"
     }
     ci_lint_ci_config_files
     ci_lint_ci_scripts
diff --git a/ci/ci_verify_cmake.sh b/ci/ci_verify_cmake.sh
index 5596735..a3f7379 100755
--- a/ci/ci_verify_cmake.sh
+++ b/ci/ci_verify_cmake.sh
@@ -39,19 +39,18 @@
         [[ $TEMP && ( $Temp || $temp ) ]] && unset TEMP
         [[ $TMP && ( $Tmp || $tmp ) ]] && unset TMP
         # Ensure that CI_CMAKE_GENERATOR_PLATFORM is initialized for this generator.
-        ci_assert "checking CI_CMAKE_GENERATOR_PLATFORM" \
-                  -n "$CI_CMAKE_GENERATOR_PLATFORM"
+        [[ $CI_CMAKE_GENERATOR_PLATFORM ]] ||
+            ci_err_internal "missing \$CI_CMAKE_GENERATOR_PLATFORM"
     fi
 }
 
 function ci_trace_build {
     ci_info "## START OF CONFIGURATION ##"
-    ci_info "host arch: $CI_HOST_ARCH"
-    ci_info "host system: $CI_HOST_SYSTEM"
-    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_HOST_SYSTEM.$CI_HOST_ARCH" ]] && {
+    ci_info "build arch: $CI_BUILD_ARCH"
+    ci_info "build system: $CI_BUILD_SYSTEM"
+    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_BUILD_SYSTEM.$CI_BUILD_ARCH" ]] && {
         ci_info "target arch: $CI_TARGET_ARCH"
         ci_info "target system: $CI_TARGET_SYSTEM"
-        ci_info "target ABI: $CI_TARGET_ABI"
     }
     ci_info "source directory: $CI_SRC_DIR"
     ci_info "build directory: $CI_BUILD_DIR"
@@ -122,8 +121,6 @@
     }
     ALL_CMAKE_VARS+=(-DCMAKE_BUILD_TYPE="$CI_CMAKE_BUILD_TYPE")
     ALL_CMAKE_VARS+=(-DCMAKE_VERBOSE_MAKEFILE=ON)
-    [[ $((CI_NO_TEST)) -ne 0 ]] &&
-        ALL_CMAKE_VARS+=(-DPNG_TESTS=OFF)
     ALL_CMAKE_VARS+=($CI_CMAKE_VARS)
     local ALL_CMAKE_BUILD_FLAGS=($CI_CMAKE_BUILD_FLAGS)
     local ALL_CTEST_FLAGS=($CI_CTEST_FLAGS)
@@ -137,48 +134,48 @@
     # instead of $CI_SRC_DIR and $CI_INSTALL_DIR from this point onwards.
     ci_spawn mkdir -p "$CI_BUILD_DIR"
     ci_spawn cd "$CI_BUILD_DIR"
-    ci_assert "checking CI_BUILD_TO_SRC_RELDIR" \
-              "$CI_SRC_DIR" -ef "$CI_BUILD_TO_SRC_RELDIR"
+    [[ $CI_BUILD_TO_SRC_RELDIR -ef $CI_SRC_DIR ]] ||
+        ci_err_internal "bad or missing \$CI_BUILD_TO_SRC_RELDIR"
     ci_spawn mkdir -p "$CI_INSTALL_DIR"
-    ci_assert "checking CI_BUILD_TO_INSTALL_RELDIR" \
-              "$CI_INSTALL_DIR" -ef "$CI_BUILD_TO_INSTALL_RELDIR"
+    [[ $CI_BUILD_TO_INSTALL_RELDIR -ef $CI_INSTALL_DIR ]] ||
+        ci_err_internal "bad or missing \$CI_BUILD_TO_INSTALL_RELDIR"
     # Spawn "cmake ...".
     ci_spawn "$CI_CMAKE" -DCMAKE_INSTALL_PREFIX="$CI_BUILD_TO_INSTALL_RELDIR" \
                          "${ALL_CMAKE_VARS[@]}" \
                          "$CI_BUILD_TO_SRC_RELDIR"
     # Spawn "cmake --build ...".
     ci_spawn "$CI_CMAKE" --build . \
-                         --config "$CI_CMAKE_BUILD_TYPE" \
+                         --config="$CI_CMAKE_BUILD_TYPE" \
                          "${ALL_CMAKE_BUILD_FLAGS[@]}"
-    [[ $((CI_NO_TEST)) -ne 0 ]] || {
+    ci_expr $((CI_NO_TEST)) || {
         # Spawn "ctest" if testing is not disabled.
-        ci_spawn "$CI_CTEST" --build-config "$CI_CMAKE_BUILD_TYPE" \
+        ci_spawn "$CI_CTEST" --build-config="$CI_CMAKE_BUILD_TYPE" \
                              "${ALL_CTEST_FLAGS[@]}"
     }
-    [[ $((CI_NO_INSTALL)) -ne 0 ]] || {
-        # Spawn "cmake --build ... --target install" if installation is not disabled.
+    ci_expr $((CI_NO_INSTALL)) || {
+        # Spawn "cmake --build ... --target=install" if installation is not disabled.
         ci_spawn "$CI_CMAKE" --build . \
-                             --config "$CI_CMAKE_BUILD_TYPE" \
-                             --target install \
+                             --config="$CI_CMAKE_BUILD_TYPE" \
+                             --target=install \
                              "${ALL_CMAKE_BUILD_FLAGS[@]}"
     }
-    [[ $((CI_NO_CLEAN)) -ne 0 ]] || {
-        # Spawn "make --build ... --target clean" if cleaning is not disabled.
+    ci_expr $((CI_NO_CLEAN)) || {
+        # Spawn "make --build ... --target=clean" if cleaning is not disabled.
         ci_spawn "$CI_CMAKE" --build . \
-                             --config "$CI_CMAKE_BUILD_TYPE" \
-                             --target clean \
+                             --config="$CI_CMAKE_BUILD_TYPE" \
+                             --target=clean \
                              "${ALL_CMAKE_BUILD_FLAGS[@]}"
     }
     ci_info "## END OF BUILD ##"
 }
 
 function main {
-    [[ $# -eq 0 ]] || {
-        ci_info "note: this program accepts environment options only"
-        ci_err "unsupported command argument: '$1'"
-    }
     ci_init_build
     ci_trace_build
+    [[ $# -eq 0 ]] || {
+        ci_info "note: this program accepts environment options only (see above)"
+        ci_err "unexpected command argument: '$1'"
+    }
     ci_cleanup_old_build
     ci_build
 }
diff --git a/ci/ci_verify_configure.sh b/ci/ci_verify_configure.sh
index 9e0d777..fa7e82e 100755
--- a/ci/ci_verify_configure.sh
+++ b/ci/ci_verify_configure.sh
@@ -22,7 +22,7 @@
 function ci_init_build {
     # Ensure that the mandatory variables are initialized.
     CI_MAKE="${CI_MAKE:-make}"
-    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_HOST_SYSTEM.$CI_HOST_ARCH" ]] || {
+    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_BUILD_SYSTEM.$CI_BUILD_ARCH" ]] || {
         # For native builds, set CI_CC to "cc" by default if the cc command is available.
         # The configure script defaults CC to "gcc", which is not always a good idea.
         [[ -x $(command -v cc) ]] && CI_CC="${CI_CC:-cc}"
@@ -36,12 +36,11 @@
 
 function ci_trace_build {
     ci_info "## START OF CONFIGURATION ##"
-    ci_info "host arch: $CI_HOST_ARCH"
-    ci_info "host system: $CI_HOST_SYSTEM"
-    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_HOST_SYSTEM.$CI_HOST_ARCH" ]] && {
+    ci_info "build arch: $CI_BUILD_ARCH"
+    ci_info "build system: $CI_BUILD_SYSTEM"
+    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_BUILD_SYSTEM.$CI_BUILD_ARCH" ]] && {
         ci_info "target arch: $CI_TARGET_ARCH"
         ci_info "target system: $CI_TARGET_SYSTEM"
-        ci_info "target ABI: $CI_TARGET_ABI"
     }
     ci_info "source directory: $CI_SRC_DIR"
     ci_info "build directory: $CI_BUILD_DIR"
@@ -107,15 +106,15 @@
     ci_spawn "$CI_SRC_DIR/configure" --prefix="$CI_INSTALL_DIR" $CI_CONFIGURE_FLAGS
     # Spawn "make".
     ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS
-    [[ $((CI_NO_TEST)) -ne 0 ]] || {
+    ci_expr $((CI_NO_TEST)) || {
         # Spawn "make test" if testing is not disabled.
         ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS test
     }
-    [[ $((CI_NO_INSTALL)) -ne 0 ]] || {
+    ci_expr $((CI_NO_INSTALL)) || {
         # Spawn "make install" if installation is not disabled.
         ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS install
     }
-    [[ $((CI_NO_CLEAN)) -ne 0 ]] || {
+    ci_expr $((CI_NO_CLEAN)) || {
         # Spawn "make clean" and "make distclean" if cleaning is not disabled.
         ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS clean
         ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS distclean
@@ -124,12 +123,12 @@
 }
 
 function main {
-    [[ $# -eq 0 ]] || {
-        ci_info "note: this program accepts environment options only"
-        ci_err "unsupported command argument: '$1'"
-    }
     ci_init_build
     ci_trace_build
+    [[ $# -eq 0 ]] || {
+        ci_info "note: this program accepts environment options only (see above)"
+        ci_err "unexpected command argument: '$1'"
+    }
     ci_cleanup_old_build
     ci_build
 }
diff --git a/ci/ci_verify_makefiles.sh b/ci/ci_verify_makefiles.sh
index ef6d783..79b97a3 100755
--- a/ci/ci_verify_makefiles.sh
+++ b/ci/ci_verify_makefiles.sh
@@ -31,12 +31,11 @@
 
 function ci_trace_build {
     ci_info "## START OF CONFIGURATION ##"
-    ci_info "host arch: $CI_HOST_ARCH"
-    ci_info "host system: $CI_HOST_SYSTEM"
-    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_HOST_SYSTEM.$CI_HOST_ARCH" ]] && {
+    ci_info "build arch: $CI_BUILD_ARCH"
+    ci_info "build system: $CI_BUILD_SYSTEM"
+    [[ "$CI_TARGET_SYSTEM.$CI_TARGET_ARCH" != "$CI_BUILD_SYSTEM.$CI_BUILD_ARCH" ]] && {
         ci_info "target arch: $CI_TARGET_ARCH"
         ci_info "target system: $CI_TARGET_SYSTEM"
-        ci_info "target ABI: $CI_TARGET_ABI"
     }
     ci_info "source directory: $CI_SRC_DIR"
     ci_info "environment option: \$CI_MAKEFILES: '$CI_MAKEFILES'"
@@ -120,14 +119,14 @@
         ci_spawn "$CI_MAKE" -f "$MY_MAKEFILE" \
                             "${ALL_MAKE_FLAGS[@]}" \
                             "${ALL_MAKE_VARS[@]}"
-        [[ $((CI_NO_TEST)) -ne 0 ]] || {
+        ci_expr $((CI_NO_TEST)) || {
             # Spawn "make test" if testing is not disabled.
             ci_spawn "$CI_MAKE" -f "$MY_MAKEFILE" \
                                 "${ALL_MAKE_FLAGS[@]}" \
                                 "${ALL_MAKE_VARS[@]}" \
                                 test
         }
-        [[ $((CI_NO_CLEAN)) -ne 0 ]] || {
+        ci_expr $((CI_NO_CLEAN)) || {
             # Spawn "make clean" if cleaning is not disabled.
             ci_spawn "$CI_MAKE" -f "$MY_MAKEFILE" \
                                 "${ALL_MAKE_FLAGS[@]}" \
@@ -139,12 +138,12 @@
 }
 
 function main {
-    [[ $# -eq 0 ]] || {
-        ci_info "note: this program accepts environment options only"
-        ci_err "unsupported command argument: '$1'"
-    }
     ci_init_build
     ci_trace_build
+    [[ $# -eq 0 ]] || {
+        ci_info "note: this program accepts environment options only (see above)"
+        ci_err "unexpected command argument: '$1'"
+    }
     ci_cleanup_old_build
     ci_build
 }
diff --git a/ci/lib/ci.lib.sh b/ci/lib/ci.lib.sh
index 29ab53a..fc3e1b6 100644
--- a/ci/lib/ci.lib.sh
+++ b/ci/lib/ci.lib.sh
@@ -30,16 +30,6 @@
 CI_BUILD_SYSTEM="${CI_BUILD_SYSTEM:-"$(uname -s | tr 'A-Z/\.-' 'a-z____')"}"
 
 # Initialize the global constants CI_TARGET_{...} for the target platform.
-if [[ $CI_TARGET_ARCH && $CI_TARGET_SYSTEM && $CI_TARGET_ABI ]]
-then
-    CI_TARGET_TRIPLET="${CI_TARGET_TRIPLET:-$CI_TARGET_ARCH-$CI_TARGET_SYSTEM-$CI_TARGET_ABI}"
-elif [[ $CI_TARGET_TRIPLET ]]
-then
-    CI_TARGET_ARCH="${CI_TARGET_ARCH:-${CI_TARGET_TRIPLET%%-*}}"
-    CI_TARGET_DOUBLET_IMPL="${CI_TARGET_TRIPLET#*-}"
-    CI_TARGET_SYSTEM="${CI_TARGET_SYSTEM:-${CI_TARGET_DOUBLET_IMPL%%-*}}"
-    CI_TARGET_ABI="${CI_TARGET_ABI:-${CI_TARGET_DOUBLET_IMPL#*-}}"
-fi
 CI_TARGET_ARCH="${CI_TARGET_ARCH:-"$CI_BUILD_ARCH"}"
 CI_TARGET_SYSTEM="${CI_TARGET_SYSTEM:-"$CI_BUILD_SYSTEM"}"
 
@@ -63,16 +53,17 @@
     exit 134
 }
 
-function ci_assert {
-    # Use the "test" built-in command instead of the "[[ ]]" syntax,
-    # to ensure the a-priori expansion of all assertion arguments.
-    # (Consistently, both "ci_assert" and "test" have a command-like behavior.)
-    [[ $# -ge 2 ]] ||
-        ci_err_internal "failed: ci_assert: bad or missing operands"
-    local label="$1"
-    shift
-    test "$@" ||
-        ci_err_internal "failed: $label:" test "$@"
+function ci_expr {
+    if [[ ${*:-0} == [0-9] ]]
+    then
+        # This is the same as in the else-branch below, albeit much faster
+        # for our intended use cases.
+        return $((!$1))
+    else
+        # The funny-looking compound command "... && return $? || return $?"
+        # allows the execution to continue uninterrupted under "set -e".
+        expr >/dev/null "$@" && return $? || return $?
+    fi
 }
 
 function ci_spawn {
@@ -83,20 +74,11 @@
 }
 
 # Ensure that the initialization is correct.
-ci_assert "checking CI_TOPLEVEL_DIR" \
-          "$CI_TOPLEVEL_DIR/ci/lib/ci.lib.sh" -ef "${BASH_SOURCE[0]}"
-ci_assert "checking CI_SCRIPT_DIR and CI_SCRIPT_NAME" \
-          "$CI_SCRIPT_DIR/$CI_SCRIPT_NAME" -ef "$0"
-ci_assert "checking CI_BUILD_ARCH and CI_BUILD_SYSTEM" \
-          -n "$CI_BUILD_ARCH" -a -n "$CI_BUILD_SYSTEM"
-ci_assert "checking CI_TARGET_ARCH and CI_TARGET_SYSTEM" \
-          -n "$CI_TARGET_ARCH" -a -n "$CI_TARGET_SYSTEM"
-ci_assert "checking CI_TARGET_TRIPLET" \
-          x"$CI_TARGET_TRIPLET" = x"" -o \
-          x"$CI_TARGET_TRIPLET" = x"$CI_TARGET_ARCH-$CI_TARGET_SYSTEM-$CI_TARGET_ABI"
-ci_assert "checking if CI_NO_TEST is boolean" \
-          $((CI_NO_TEST)) -eq $((!!CI_NO_TEST))
-ci_assert "checking if CI_NO_INSTALL is boolean" \
-          $((CI_NO_INSTALL)) -eq $((!!CI_NO_INSTALL))
-ci_assert "checking if CI_NO_CLEAN is boolean" \
-          $((CI_NO_CLEAN)) -eq $((!!CI_NO_CLEAN))
+[[ $CI_TOPLEVEL_DIR/ci/lib/ci.lib.sh -ef ${BASH_SOURCE[0]} ]] ||
+    ci_err_internal "bad or missing \$CI_TOPLEVEL_DIR"
+[[ $CI_SCRIPT_DIR/$CI_SCRIPT_NAME -ef $0 ]] ||
+    ci_err_internal "bad or missing \$CI_SCRIPT_DIR/\$CI_SCRIPT_NAME"
+[[ $CI_BUILD_ARCH && $CI_BUILD_SYSTEM ]] ||
+    ci_err_internal "missing \$CI_BUILD_ARCH or \$CI_BUILD_SYSTEM"
+[[ $CI_TARGET_ARCH && $CI_TARGET_SYSTEM ]] ||
+    ci_err_internal "missing \$CI_TARGET_ARCH or \$CI_TARGET_SYSTEM"