Customizable error messages for missing prereqs.

Adds the FindRequiredPackage() macro that wraps the functionality
of the standard find_package() macro.

CMakeLists.txt

@@ -1,6 +1,4 @@
-########################################################################
-## CMake Configuration
-
+######################################################################## ## CMake Configuration 
 cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
 
 # Prohibit in-source builds.
@@ -46,6 +44,8 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${EXTRA_COMPILE_FLAGS}")
 ########################################################################
 ## Dependency Configuration
 
+include(FindRequiredPackage)
+
 # Check cache value first to avoid displaying "Found sed" messages everytime
 if (NOT SED_EXE)
     find_program(SED_EXE sed)
@@ -56,17 +56,24 @@ if (NOT SED_EXE)
     endif ()
 endif ()
 
-find_package(Perl REQUIRED)
-find_package(FLEX REQUIRED)
-find_package(BISON REQUIRED)
-find_package(PCAP REQUIRED)
-find_package(OpenSSL REQUIRED)
-find_package(BIND REQUIRED)
+FindRequiredPackage(Perl)
+FindRequiredPackage(FLEX)
+FindRequiredPackage(BISON)
+FindRequiredPackage(PCAP)
+FindRequiredPackage(OpenSSL)
+FindRequiredPackage(BIND)
 
 if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/aux/binpac/CMakeLists.txt)
     add_subdirectory(aux/binpac)
 endif ()
-find_package(BinPAC REQUIRED)
+FindRequiredPackage(BinPAC)
+
+if (MISSING_PREREQS)
+    foreach (prereq ${MISSING_PREREQ_DESCS})
+        message(SEND_ERROR ${prereq})
+    endforeach ()
+    message(FATAL_ERROR "Configuration aborted due to missing prerequisites")
+endif ()
 
 include_directories(BEFORE
                     ${PCAP_INCLUDE_DIR}

cmake/FindLibGeoIP.cmake

@@ -13,7 +13,7 @@
 #
 # Variables defined by this module:
 #
-#  LIBGeoIP_FOUND              System has GeoIP libraries and headers
+#  LIBGEOIP_FOUND              System has GeoIP libraries and headers
 #  LibGeoIP_LIBRARY            The GeoIP library
 #  LibGeoIP_INCLUDE_DIR        The location of GeoIP headers
 

cmake/FindOpenSSL.cmake

@@ -13,7 +13,7 @@
 #
 # Variables defined by this module:
 #
-#  OpenSSL_FOUND             System has openssl, include and library dirs found
+#  OPENSSL_FOUND             System has openssl, include and library dirs found
 #  OpenSSL_INCLUDE_DIR       The openssl include directories. 
 #  OpenSSL_LIBRARIES         The openssl libraries.
 #  OpenSSL_CYRPTO_LIBRARY    The openssl crypto library.

cmake/FindRequiredPackage.cmake

@@ -0,0 +1,44 @@
+# A wrapper macro around the standard CMake find_package macro that
+# facilitates displaying better error messages by default, or even
+# accepting custom error messages on a per package basis.
+#
+# If a package is not found, then the MISSING_PREREQS variable gets
+# set to true and either a default or custom error message appended
+# to MISSING_PREREQ_DESCS.
+#
+# The caller can use these variables to display a list of any missing
+# packages and abort the build/configuration if there were any.
+# 
+# Use as follows:
+#
+# include(FindRequiredPackage)
+# FindRequiredPackage(Perl)
+# FindRequiredPackage(FLEX "You need to install flex (Fast Lexical Analyzer)")
+#
+# if (MISSING_PREREQS)
+#    foreach (prereq ${MISSING_PREREQ_DESCS})
+#        message(SEND_ERROR ${prereq})
+#    endforeach ()
+#    message(FATAL_ERROR "Configuration aborted due to missing prerequisites")
+# endif ()
+
+macro(FindRequiredPackage packageName)
+    find_package(${packageName})
+    string(TOUPPER ${packageName} canonPackageName)
+    if (NOT ${canonPackageName}_FOUND)
+        set(MISSING_PREREQS true)
+
+        set(customDesc)
+        foreach (descArg ${ARGN})
+            set(customDesc "${customDesc} ${descArg}")
+        endforeach ()
+
+        if (customDesc)
+            # append the custom error message that was provided as an argument
+            list(APPEND MISSING_PREREQ_DESCS ${customDesc})
+        else ()
+            list(APPEND MISSING_PREREQ_DESCS
+                 " Could not find prerequisite package '${packageName}'")
+        endif ()
+    endif ()
+endmacro(FindRequiredPackage)