Consider included .inc files as being exported by default.

core/org.eclipse.cdt.core/plugin.xml

@@ -378,6 +378,10 @@
             type="text"
             extension="hpp">
       </fileTypes>
+      <fileTypes
+            type="text"
+            extension="inc">
+      </fileTypes>
       <fileTypes
             type="binary"
             extension="o">
@@ -514,7 +518,7 @@
 	  <!-- declares a content type for C++ header files -->
       <content-type id="cxxHeader" name="%cxxHeaderName" 
           base-type="org.eclipse.cdt.core.cxxSource"
-		  file-extensions="h,hpp,hh,hxx"          
+		  file-extensions="h,hpp,hh,hxx,inc"          
           priority="high"/>
 	  <!-- declares a content type for ASM Source files -->
       <content-type id="asmSource" name="%asmSourceName" 

core/org.eclipse.cdt.ui/plugin.xml

@@ -1685,7 +1685,7 @@
          point="org.eclipse.compare.contentMergeViewers">
       <viewer
             class="org.eclipse.cdt.internal.ui.compare.CContentViewerCreator"
-            extensions="c,cc,cxx,cpp,c++,h,hh,hxx,hpp,c2"
+            extensions="c,cc,cxx,cpp,c++,h,hh,hxx,hpp,inc,c2"
             id="org.eclipse.cdt.ui.compare.CContentViewerCreator">
       </viewer>
       <contentTypeBinding
@@ -3192,7 +3192,7 @@
       <page
             canSearchEnclosingProjects="true"
             class="org.eclipse.cdt.internal.ui.search.CSearchPage"
-            extensions="c:90,cpp:90, cxx:90, cc:90,C:90, h:90, hh:90, hpp:90, H:90"
+            extensions="c:90,cpp:90,cxx:90,cc:90,C:90,h:90,hh:90,hpp:90,H:90,inc:90"
             icon="icons/obj16/csearch_obj.gif"
             id="org.eclipse.cdt.ui.pdomSearchPage"
             label="%CSearchPage.label"

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/refactoring/includes/IncludeCreationContext.java

@@ -26,6 +26,7 @@ import org.eclipse.cdt.core.index.IIndexFile;
 import org.eclipse.cdt.core.index.IIndexInclude;
 import org.eclipse.cdt.core.index.IndexLocationFactory;
 import org.eclipse.cdt.core.model.ITranslationUnit;
+import org.eclipse.cdt.core.parser.util.ArrayUtil;
 
 import org.eclipse.cdt.internal.corext.codemanipulation.InclusionContext;
 
@@ -80,7 +81,7 @@ public class IncludeCreationContext extends InclusionContext {
 					queue.add(file);
 					while ((file = queue.pollFirst()) != null) {
 						for (IIndexInclude include : file.getIncludes()) {
-							if (getPreferences().allowIndirectInclusion || include.isIncludedFileExported()) {
+							if (getPreferences().allowIndirectInclusion || isIncludedFileExported(include)) {
 								file = fIndex.resolveInclude(include);
 								if (file != null) {
 									if (exportedHeaders.add(getPath(file)))
@@ -95,6 +96,15 @@ public class IncludeCreationContext extends InclusionContext {
 		fHeadersToInclude.removeAll(exportedHeaders);
 	}
 
+	private boolean isIncludedFileExported(IIndexInclude include) throws CoreException {
+		if (include.isIncludedFileExported())
+			return true;
+		String name = include.getName();
+		int index = name.lastIndexOf('.');
+		String extension = index >= 0 ? name.substring(index + 1) : ""; //$NON-NLS-1$
+		return ArrayUtil.containsEqual(getPreferences().extensionsOfAutoExportedFiles, extension);
+	}
+
 	private static IPath getPath(IIndexFile file) throws CoreException {
 		return IndexLocationFactory.getAbsolutePath(file.getLocation());
 	}

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/refactoring/includes/IncludePreferences.java

@@ -31,6 +31,7 @@ import org.eclipse.cdt.internal.ui.refactoring.includes.IncludeGroupStyle.Includ
  */
 public class IncludePreferences implements Comparator<StyledInclude> {
 	private static final String DEFAULT_PARTNER_FILE_SUFFIXES = "test,unittest"; //$NON-NLS-1$
+	private static final String DEFAULT_EXTENSIONS_OF_AUTO_EXPORTED_FILES = "inc"; //$NON-NLS-1$
 
 	public static enum UnusedStatementDisposition { REMOVE, COMMENT_OUT, KEEP }
 
@@ -48,6 +49,7 @@ public class IncludePreferences implements Comparator<StyledInclude> {
 	public final boolean assumeTemplatesMayBeForwardDeclared;
 	public final UnusedStatementDisposition unusedStatementsDisposition;
 	public final String[] partnerFileSuffixes;
+	public final String[] extensionsOfAutoExportedFiles;
 
 	public IncludePreferences(ICProject project) {
 		includeStyles = new HashMap<IncludeKind, IncludeGroupStyle>();
@@ -94,6 +96,11 @@ public class IncludePreferences implements Comparator<StyledInclude> {
 				PreferenceConstants.INCLUDES_PARTNER_FILE_SUFFIXES, project, DEFAULT_PARTNER_FILE_SUFFIXES);
 		partnerFileSuffixes = value.split(","); //$NON-NLS-1$
 		
+		value = PreferenceConstants.getPreference(
+				PreferenceConstants.INCLUDES_EXTENSIONS_OF_AUTO_EXPORTED_FILES, project,
+				DEFAULT_EXTENSIONS_OF_AUTO_EXPORTED_FILES);
+		extensionsOfAutoExportedFiles = value.split(","); //$NON-NLS-1$
+
 		heuristicHeaderSubstitution = PreferenceConstants.getPreference(
 				PreferenceConstants.INCLUDES_HEURISTIC_HEADER_SUBSTITUTION, project, true);
 
@@ -171,6 +178,8 @@ public class IncludePreferences implements Comparator<StyledInclude> {
 		store.setDefault(PreferenceConstants.INCLUDE_STYLE_MATCHING_PATTERN, ""); //$NON-NLS-1$
 
 		store.setDefault(PreferenceConstants.INCLUDES_PARTNER_FILE_SUFFIXES, DEFAULT_PARTNER_FILE_SUFFIXES);
+		store.setDefault(PreferenceConstants.INCLUDES_EXTENSIONS_OF_AUTO_EXPORTED_FILES,
+				DEFAULT_EXTENSIONS_OF_AUTO_EXPORTED_FILES);
 		store.setDefault(PreferenceConstants.INCLUDES_HEURISTIC_HEADER_SUBSTITUTION, true);
 		store.setDefault(PreferenceConstants.INCLUDES_ALLOW_REORDERING, true);
 		store.setDefault(PreferenceConstants.INCLUDES_ALLOW_PARTNER_INDIRECT_INCLUSION, true);

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/ui/PreferenceConstants.java

@@ -1935,12 +1935,20 @@ public class PreferenceConstants {
 	/**
 	 * Defines a list of file name suffixes. A header file and the including file are considered
 	 * partners if their file names without extensions are either identical or differ by one of
-	 * these suffixes.  
+	 * these suffixes.
 	 *
 	 * @since 5.6
 	 */
 	public static final String INCLUDES_PARTNER_FILE_SUFFIXES = "includes.partnerFileSuffixes"; //$NON-NLS-1$
 
+	/**
+	 * Defines a list of file name extensions. An included file is considered exported by default if it has
+	 * one of the specified name extensions.
+	 *
+	 * @since 5.10
+	 */
+	public static final String INCLUDES_EXTENSIONS_OF_AUTO_EXPORTED_FILES = "includes.extensionsOfAutoExportedFiles"; //$NON-NLS-1$
+
 	/**
 	 * Whether a heuristic approach should be used to decide which C++ header files to include.
 	 * The heuristic prefers headers which have no file extension and / or are named like the symbol