--- a/python/mozbuild/mozbuild/backend/cpp_eclipse.py
+++ b/python/mozbuild/mozbuild/backend/cpp_eclipse.py
@@ -91,22 +91,32 @@ class CppEclipseBackend(CommonBackend):
         formatter_prefs_path = os.path.join(settings_dir, 'org.eclipse.cdt.core.prefs')
         with open(formatter_prefs_path, 'wb') as fh:
             fh.write(FORMATTER_SETTINGS);
 
         editor_prefs_path = os.path.join(workspace_settings_dir, "org.eclipse.ui.editors.prefs");
         with open(editor_prefs_path, 'wb') as fh:
             fh.write(EDITOR_SETTINGS);
 
+    def _define_entry(self, name, value):
+        define = ET.Element('entry')
+        define.set('kind', 'macro')
+        define.set('name', name)
+        define.set('value', value)
+        return ET.tostring(define)
+
     def _write_language_settings(self, fh):
         settings = LANGUAGE_SETTINGS_TEMPLATE
 
         settings = settings.replace('@GLOBAL_INCLUDE_PATH@', os.path.join(self.environment.topobjdir, 'dist/include'))
+        settings = settings.replace('@NSPR_INCLUDE_PATH@', os.path.join(self.environment.topobjdir, 'dist/include/nspr'))
         settings = settings.replace('@IPDL_INCLUDE_PATH@', os.path.join(self.environment.topobjdir, 'ipc/ipdl/_ipdlheaders'))
         settings = settings.replace('@PREINCLUDE_FILE_PATH@', os.path.join(self.environment.topobjdir, 'dist/include/mozilla-config.h'))
+        settings = settings.replace('@DEFINE_MOZILLA_INTERNAL_API@', self._define_entry('MOZILLA_INTERNAL_API', '1'))
+        settings = settings.replace('@DEFINE_MDCPUCFG@', self._define_entry('MDCPUCFG', self.environment.substs['TARGET_NSPR_MDCPUCFG']))
 
         fh.write(settings)
 
     def _write_launch_files(self, launch_dir):
         main_gecko_launch = os.path.join(launch_dir, 'gecko.launch')
         with open(main_gecko_launch, 'wb') as fh:
             bin_dir = os.path.join(self.environment.topobjdir, 'dist')
 
@@ -275,29 +285,33 @@ LANGUAGE_SETTINGS_TEMPLATE = """<?xml ve
         <configuration id="0.1674256904" name="Default">
                 <extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
                         <provider class="org.eclipse.cdt.core.language.settings.providers.LanguageSettingsGenericProvider" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider" name="CDT User Setting Entries" prefer-non-shared="true" store-entries-with-project="true">
                                 <language id="org.eclipse.cdt.core.g++">
                                         <resource project-relative-path="">
                                                 <entry kind="includePath" name="@GLOBAL_INCLUDE_PATH@">
                                                         <flag value="LOCAL"/>
                                                 </entry>
+                                                <entry kind="includePath" name="@NSPR_INCLUDE_PATH@">
+                                                        <flag value="LOCAL"/>
+                                                </entry>
                                                 <entry kind="includePath" name="@IPDL_INCLUDE_PATH@">
                                                         <flag value="LOCAL"/>
                                                 </entry>
                                                 <entry kind="includeFile" name="@PREINCLUDE_FILE_PATH@">
                                                         <flag value="LOCAL"/>
                                                 </entry>
                                                 <!--
                                                   Because of https://developer.mozilla.org/en-US/docs/Eclipse_CDT#Headers_are_only_parsed_once
                                                   we need to make sure headers are parsed with MOZILLA_INTERNAL_API to make sure
                                                   the indexer gets the version that is used in most of the true. This means that
                                                   MOZILLA_EXTERNAL_API code will suffer.
                                                 -->
-                                                <entry kind="macro" name="MOZILLA_INTERNAL_API" value="1"/>
+                                                @DEFINE_MOZILLA_INTERNAL_API@
+                                                @DEFINE_MDCPUCFG@
                                         </resource>
                                 </language>
                         </provider>
                         <provider class="org.eclipse.cdt.internal.build.crossgcc.CrossGCCBuiltinSpecsDetector" console="false" env-hash="-859273372804152468" id="org.eclipse.cdt.build.crossgcc.CrossGCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT Cross GCC Built-in Compiler Settings" parameter="${COMMAND} ${FLAGS} -E -P -v -dD &quot;${INPUTS}&quot; -std=c++11" prefer-non-shared="true" store-entries-with-project="true">
                              <language-scope id="org.eclipse.cdt.core.gcc"/>
                              <language-scope id="org.eclipse.cdt.core.g++"/>
                         </provider>
                         <provider-reference id="org.eclipse.cdt.managedbuilder.core.MBSLanguageSettingsProvider" ref="shared-provider"/>