[ci] Add unit test for banned keywords

Flags use of keywords representing deprecated or other
"to be avoided" methods, e.g. use of DBL_MAX instead of
the type-safe std::numeric_limits<double>::max() method.

tests/code_layout/CMakeLists.txt

@@ -2,6 +2,7 @@ IF(WITH_ASTYLE)
   ADD_TEST(qgis_indentation ${CMAKE_SOURCE_DIR}/scripts/verify-indentation.sh)
 ENDIF(WITH_ASTYLE)
 
+ADD_TEST(qgis_banned_keywords ${CMAKE_SOURCE_DIR}/tests/code_layout/test_banned_keywords.sh)
 ADD_TEST(qgis_licenses ${CMAKE_SOURCE_DIR}/tests/code_layout/test_licenses.sh)
 ADD_TEST(qgis_spelling ${CMAKE_SOURCE_DIR}/scripts/spell_check/spell_test.sh)
 

tests/code_layout/test_banned_keywords.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+
+# This test checks for use of deprecated/outdated methods and suggests their replacement
+
+declare -a KEYWORDS=()
+declare -a HINTS=()
+
+KEYWORDS[0]="DBL_MAX"
+HINTS[0]="Use the type-safe method std::numeric_limits<double>::max() instead"
+
+KEYWORDS[1]="DBL_MIN"
+HINTS[1]="Use the type-safe method std::numeric_limits<double>::lowest() instead"
+
+KEYWORDS[2]="DBL_EPSILON"
+HINTS[2]="Use the type-safe method std::numeric_limits<double>::epsilon() instead"
+
+RES=
+DIR=$(git rev-parse --show-toplevel)
+
+pushd "${DIR}" > /dev/null || exit
+
+for i in "${!KEYWORDS[@]}"
+do
+  FOUND=$(git grep "${KEYWORDS[$i]}" -- 'src/*.h' 'src/*.cpp')
+
+  if [[  ${FOUND} ]]; then
+    echo "Found source files with banned keyword: ${KEYWORDS[$i]}!"
+    echo " -> ${HINTS[$i]}"
+    echo
+    echo "${FOUND}"
+    echo
+    RES=1
+  fi
+
+done
+
+popd > /dev/null || exit
+
+if [ $RES ]; then
+  echo " *** Found banned keywords"
+  exit 1
+fi
+