compile-options: Refactor/document dependencies

Ticket: ENT-12600
Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>

Author: larsewi

build-scripts/compile-options

@@ -103,51 +103,81 @@ export DEB_LDFLAGS_APPEND
 ############### Fill in build dependencies in DEPS variable ################
 
 DEPS=
-[ "$OS_FAMILY" = mingw ]  &&  var_append DEPS "pthreads-w32 libgnurx"
 
-# libgcc_s.so is needed before we compile any other dependency
-#             on some platforms!
-case "$OS_FAMILY" in
-    solaris|aix)  var_append DEPS "libgcc" ;;
-esac
+# Windows specific dependencies
+if [ "$OS_FAMILY" = mingw ]; then
+    # Win32 does not support pthreads natively. The pthreads-w32 project provide
+    # solution to this problem.
+    var_append DEPS "pthreads-w32"
 
-var_append DEPS "lmdb pcre2"
-
-if ! [ "$SYSTEM_SSL" = 1 ]
-then
-  # FIXME: Why do we need zlib?
-  # ANSWER: Openssl uses it optionally, TODO DISABLE
-  var_append DEPS "zlib openssl"
+    # A port of the regex functionality from the glibc Library for use on
+    # Windows platforms
+    var_append DEPS "libgnurx"
 fi
 
-# libsasl needed for solaris
+# AIX / Solaris specific dependencies
 case "$OS_FAMILY" in
-    solaris|hpux)  var_append DEPS "sasl2" ;;
-esac
+    solaris|aix)
 
-# iconv is needed for libxml2 on some platforms
-case "$OS_FAMILY" in
-   aix|solaris)  var_append DEPS "libiconv" ;;
+        # libgcc_s.so is needed before we compile any other dependency
+        #             on some platforms!
+        var_append DEPS "libgcc"
+
+        # iconv is needed for libxml2 on some platforms
+        var_append DEPS "libiconv"
+        ;;
 esac
 
-var_append DEPS "libxml2 libyaml"
-var_append DEPS "diffutils"
-var_append DEPS "librsync"
+# We use system bundled SSL on RHEL >= 8
+if ! [ "$SYSTEM_SSL" = 1 ]
+then
+  # zlib is a compression library witch is a dependency of OpenSSL. However,
+  # can we remove it (CFE-4013)?
+  var_append DEPS "zlib"
 
-# LDAP functions in the agent
-# and LDAP authentication functionality in Mission Portal
-case "$PROJECT" in
-    nova)  var_append DEPS "openldap"
-esac
+  # Toolkit for TLS
+  var_append DEPS "openssl"
+fi
 
-case "$PROJECT" in
-    nova)  var_append DEPS "leech"
+# Solaris / HP-UX specific dependencies
+case "$OS_FAMILY" in
+    solaris|hpux)
+        # Generic library that implements the Simple Authentication and Security
+        # Layer (SASL) framework
+        var_append DEPS "sasl2"
+        ;;
 esac
 
-# libacl & libattr - not for the exotics (linux only?)
+# Common dependencies
+var_append DEPS "libxml2"   # Library for parsing XML
+var_append DEPS "libyaml"   # Library for parsing YAML
+var_append DEPS "diffutils" # Library for comparing files
+var_append DEPS "librsync"  # Library for synchronization of files
+var_append DEPS "lmdb"      # Library for key-value store
+var_append DEPS "pcre2"     # Library for compiling/matching regex
+
+# Enterprise only dependencies
+if [ "$PROJECT" = nova ]; then
+    # Used for storing accounts, passwords and group memberships
+    # - Agent has LDAP related policy functions
+    # - Mission Portal uses LDAP for authentication functionality
+    var_append DEPS "openldap"
+
+    # Used for efficient synchronization of tabular data
+    var_append DEPS "leech"
+fi
+
+# Non-exotics dependencies
 case "$OS_FAMILY" in
-  hpux|aix|solaris|freebsd|mingw)       ;;
-  *)  var_append DEPS "libattr libacl"  ;;
+    hpux|aix|solaris|freebsd|mingw)
+        ;;
+    *)
+        # Library for managing Extended Attributes (xattrs) on filesystems
+        var_append DEPS "libattr"
+
+        # POSIX Access Control Lists (ACLs) on filesystems
+        var_append DEPS "libacl"
+        ;;
 esac
 
 # ROLE
@@ -215,32 +245,47 @@ export ROLE
 case "$ROLE" in
     # HUB-ONLY dependencies
     hub)
-        var_append DEPS "libcurl-hub"
-        var_append DEPS "nghttp2 libexpat apr apr-util apache git rsync"
-        var_append DEPS "postgresql php"
+        # Note that we make a separate curl package for the hub. This is because
+        # the hub will include the curl binary, but we don't want that for the
+        # clients.
+        var_append DEPS "libcurl-hub"  # Provides API for performing network requests
+        var_append DEPS "nghttp2"      # Provides implementation of the HTTP/2 protocol.
+        var_append DEPS "libexpat"     # Provides stream-oriented XML parser
+        var_append DEPS "apr apr-util" # Provides a common interface to underlying OS features (used by Apache)
+        var_append DEPS "apache"       # Provides HTTP server
+        var_append DEPS "git"          # Provides a version control system
+        var_append DEPS "rsync"        # Binary to efficiently synchronize files
+        var_append DEPS "postgresql"   # Relational database
+        var_append DEPS "php"          # Scripting language for web development
         ;;
     # AGENT-ONLY dependencies
     agent)
-        var_append DEPS "libcurl"
+        var_append DEPS "libcurl"      # Provides API for performing network requests
         ;;
 esac
 
+# Make sure init.d script and systemd service is used where needed.
+#
+# We install in all Linux platforms, because it does no harm on platforms
+# without systemd, and it has the advantage of working out of the box on
+# platforms that adopt systemd later.
+if [ "$OS_FAMILY" = linux ]; then
+    WITH_SYSTEMD=yes
+else
+    WITH_SYSTEMD=no
+fi
 
-# systemd is not a build dependency, but should we generate
-# unit files for it?
-case "$OS_FAMILY" in
-  linux)  WITH_SYSTEMD=yes;;
-  *)      WITH_SYSTEMD=no;;
-esac
-
-
+# Determine whether or not to run tests
 case "$OS_FAMILY" in
-    mingw|freebsd)  TESTS=no  ;;
-    *)              TESTS=all ;;
+    mingw|freebsd)
+        TESTS=no
+        ;;
+    *)
+        TESTS=all
+        ;;
 esac
 export TESTS
 
-
 # Don't let existing LD_LIBRARY_PATH variables disturb the build.
 # Java sets this when Jenkins launches it.
 # PS! Solaris shell returns false if the var is already unset.