Implement basic objc executable linking in the CROSSTOOL.

The following link features are *not* implemented yet:
1) Objc++ linking semantics
2) Dead stripping
3) --should_prioritize_static_libs
4) DSYM generation
5) Coverage support
6) Swift interop
7) Linkmap

--
MOS_MIGRATED_REVID=139232434

10 files changed, 610 insertions, 253 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
index ca464d2a1b..bf9e7c5367 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
@@ -1150,7 +1150,7 @@ public class CcToolchainFeatures implements Serializable {
        * Add a variable that expands a flag group containing a reference to {@code name} for each
        * entry in {@code values}.
        */
-      public Builder addSequenceVariable(String name, Collection<String> values) {
+      public Builder addSequenceVariable(String name, Iterable<String> values) {
         StringSequence.Builder sequenceBuilder = new StringSequence.Builder();
         for (String value : values) {
           sequenceBuilder.addValue(value);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkAction.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkAction.java
index 44004745a0..04dc86895e 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkAction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkAction.java
@@ -95,6 +95,7 @@ public final class CppLinkAction extends AbstractAction
   private static final String LINK_GUID = "58ec78bd-1176-4e36-8143-439f656b181d";
   private static final String FAKE_LINK_GUID = "da36f819-5a15-43a9-8a45-e01b60e10c8b";
   
+  @Nullable private final String mnemonic;
   private final CppConfiguration cppConfiguration;
   private final LibraryToLink outputLibrary;
   private final Artifact linkOutput;
@@ -138,6 +139,7 @@ public final class CppLinkAction extends AbstractAction
    */
   CppLinkAction(
       ActionOwner owner,
+      String mnemonic,
       Iterable<Artifact> inputs,
       ImmutableList<Artifact> outputs,
       CppConfiguration cppConfiguration,
@@ -151,6 +153,11 @@ public final class CppLinkAction extends AbstractAction
       Map<String, String> toolchainEnv,
       ImmutableSet<String> executionRequirements) {
     super(owner, inputs, outputs);
+    if (mnemonic == null) {
+      this.mnemonic = (isLTOIndexing) ? "CppLTOIndexing" : "CppLink";
+    } else {
+      this.mnemonic = mnemonic;
+    }
     this.mandatoryInputs = inputs;
     this.cppConfiguration = cppConfiguration;
     this.outputLibrary = outputLibrary;
@@ -457,7 +464,7 @@ public final class CppLinkAction extends AbstractAction
 
   @Override
   public String getMnemonic() {
-    return (isLTOIndexing) ? "CppLTOIndexing" : "CppLink";
+    return mnemonic;
   }
 
   @Override
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
index f2690c6062..9fe8673389 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
@@ -124,6 +124,7 @@ public class CppLinkActionBuilder {
   @Nullable private final RuleContext ruleContext;
   private final AnalysisEnvironment analysisEnvironment;
   private final Artifact output;
+  @Nullable private String mnemonic;
 
   // can be null for CppLinkAction.createTestBuilder()
   @Nullable private final CcToolchainProvider toolchain;
@@ -162,7 +163,7 @@ public class CppLinkActionBuilder {
   private Iterable<LTOBackendArtifacts> allLTOArtifacts = null;
   
   private final List<VariablesExtension> variablesExtensions = new ArrayList<>();
-  private final List<Artifact> linkActionInputs = new ArrayList<>();
+  private final NestedSetBuilder<Artifact> linkActionInputs = NestedSetBuilder.stableOrder();
 
   /**
    * Creates a builder that builds {@link CppLinkAction} instances.
@@ -442,8 +443,11 @@ public class CppLinkActionBuilder {
 
   /** Builds the Action as configured and returns it. */
   public CppLinkAction build() throws InterruptedException {
-    Preconditions.checkState(
-        (libraryIdentifier == null) == (linkType == LinkTargetType.EXECUTABLE));
+    // Executable links do not have library identifiers.
+    boolean hasIdentifier = (libraryIdentifier != null);
+    boolean isExecutable = linkType.isExecutable();
+    Preconditions.checkState(hasIdentifier != isExecutable);    
+
     if (interfaceOutput != null && (fake || linkType != LinkTargetType.DYNAMIC_LIBRARY)) {
       throw new RuntimeException(
           "Interface output can only be used " + "with non-fake DYNAMIC_LIBRARY targets");
@@ -485,7 +489,7 @@ public class CppLinkActionBuilder {
       }
     }
 
-    final LibraryToLink outputLibrary = linkType == LinkTargetType.EXECUTABLE
+    final LibraryToLink outputLibrary = linkType.isExecutable()
         ? null
         : LinkerInputs.newInputLibrary(output,
             linkType.getLinkerOutput(),
@@ -651,7 +655,7 @@ public class CppLinkActionBuilder {
     NestedSetBuilder<Artifact> dependencyInputsBuilder = NestedSetBuilder.stableOrder();
     dependencyInputsBuilder.addTransitive(crosstoolInputs);
     dependencyInputsBuilder.add(toolchain.getLinkDynamicLibraryTool());
-    dependencyInputsBuilder.addAll(linkActionInputs);
+    dependencyInputsBuilder.addTransitive(linkActionInputs.build());
     if (runtimeMiddleman != null) {
       dependencyInputsBuilder.add(runtimeMiddleman);
     }
@@ -737,6 +741,7 @@ public class CppLinkActionBuilder {
 
     return new CppLinkAction(
         getOwner(),
+        mnemonic,
         inputsBuilder.deduplicate().build(),
         actionOutputs,
         cppConfiguration,
@@ -840,6 +845,12 @@ public class CppLinkActionBuilder {
   protected ActionOwner getOwner() {
     return ruleContext.getActionOwner();
   }
+  
+  /** Sets the mnemonic for the link action. */
+  public CppLinkActionBuilder setMnemonic(String mnemonic) {
+    this.mnemonic = mnemonic;
+    return this;
+  }
 
   /** Set the crosstool inputs required for the action. */
   public CppLinkActionBuilder setCrosstoolInputs(NestedSet<Artifact> inputs) {
@@ -1143,12 +1154,28 @@ public class CppLinkActionBuilder {
   }
   
   /**
-   * Sets extra input artifacts to the link action.
+   * Adds an extra input artifact to the link action.
+   */
+  public CppLinkActionBuilder addActionInput(Artifact input) {
+    this.linkActionInputs.add(input);
+    return this;
+  }
+  
+  /**
+   * Adds extra input artifacts to the link action.
    */
-  public CppLinkActionBuilder addActionInputs(Collection<Artifact> inputs) {
+  public CppLinkActionBuilder addActionInputs(Iterable<Artifact> inputs) {
     this.linkActionInputs.addAll(inputs);
     return this;
   }
+  
+  /**
+   * Adds extra input artifacts to the link actions.
+   */
+  public CppLinkActionBuilder addTransitiveActionInputs(NestedSet<Artifact> inputs) {
+    this.linkActionInputs.addTransitive(inputs);
+    return this;
+  }
 
   private static class LinkArgCollector {
     String rpathRoot;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/Link.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/Link.java
index ec51c8413f..74f33ab913 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/Link.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/Link.java
@@ -103,6 +103,14 @@ public abstract class Link {
     STATIC,
     DYNAMIC
   }
+  
+  /**
+   * Whether a particular link target is executable.
+   */
+  public enum Executable {
+    EXECUTABLE,
+    NOT_EXECUTABLE
+  }
 
   /**
    * Types of ELF files that can be created by the linker (.a, .so, .lo,
@@ -115,7 +123,8 @@ public abstract class Link {
         Staticness.STATIC,
         "c++-link-static-library",
         Picness.NOPIC,
-        ArtifactCategory.STATIC_LIBRARY),
+        ArtifactCategory.STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
     
     /** An objc static archive. */
     OBJC_ARCHIVE(
@@ -123,19 +132,35 @@ public abstract class Link {
         Staticness.STATIC, 
         "objc-archive", 
         Picness.NOPIC,
-        ArtifactCategory.STATIC_LIBRARY),
+        ArtifactCategory.STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
     
     /** An objc fully linked static archive. */
     OBJC_FULLY_LINKED_ARCHIVE(
-        ".a", Staticness.STATIC, "objc-fully-link", Picness.NOPIC, ArtifactCategory.STATIC_LIBRARY),
+        ".a",
+        Staticness.STATIC,
+        "objc-fully-link",
+        Picness.NOPIC,
+        ArtifactCategory.STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
+    /** An objc executable. */
+    OBJC_EXECUTABLE(
+        "",
+        Staticness.STATIC,
+        "objc-executable",
+        Picness.NOPIC,
+        ArtifactCategory.EXECUTABLE,
+        Executable.EXECUTABLE),
+    
     /** A static archive with .pic.o object files (compiled with -fPIC). */
     PIC_STATIC_LIBRARY(
         ".pic.a",
         Staticness.STATIC,
         "c++-link-pic-static-library",
         Picness.PIC,
-        ArtifactCategory.STATIC_LIBRARY),
+        ArtifactCategory.STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
     /** An interface dynamic library. */
     INTERFACE_DYNAMIC_LIBRARY(
@@ -143,7 +168,8 @@ public abstract class Link {
         Staticness.DYNAMIC,
         "c++-link-interface-dynamic-library",
         Picness.NOPIC,  // Actually PIC but it's not indicated in the file name
-        ArtifactCategory.INTERFACE_LIBRARY),
+        ArtifactCategory.INTERFACE_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
     /** A dynamic library. */
     DYNAMIC_LIBRARY(
@@ -151,7 +177,8 @@ public abstract class Link {
         Staticness.DYNAMIC,
         "c++-link-dynamic-library",
         Picness.NOPIC,  // Actually PIC but it's not indicated in the file name
-        ArtifactCategory.DYNAMIC_LIBRARY),
+        ArtifactCategory.DYNAMIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
     /** A static archive without removal of unused object files. */
     ALWAYS_LINK_STATIC_LIBRARY(
@@ -159,7 +186,8 @@ public abstract class Link {
         Staticness.STATIC,
         "c++-link-alwayslink-static-library",
         Picness.NOPIC,
-        ArtifactCategory.ALWAYSLINK_STATIC_LIBRARY),
+        ArtifactCategory.ALWAYSLINK_STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
     /** A PIC static archive without removal of unused object files. */
     ALWAYS_LINK_PIC_STATIC_LIBRARY(
@@ -167,7 +195,8 @@ public abstract class Link {
         Staticness.STATIC,
         "c++-link-alwayslink-pic-static-library",
         Picness.PIC,
-        ArtifactCategory.ALWAYSLINK_STATIC_LIBRARY),
+        ArtifactCategory.ALWAYSLINK_STATIC_LIBRARY,
+        Executable.NOT_EXECUTABLE),
 
     /** An executable binary. */
     EXECUTABLE(
@@ -175,25 +204,29 @@ public abstract class Link {
         Staticness.DYNAMIC,
         "c++-link-executable",
         Picness.NOPIC,  // Picness is not indicate in the file name
-        ArtifactCategory.EXECUTABLE);
+        ArtifactCategory.EXECUTABLE,
+        Executable.EXECUTABLE);
 
     private final String extension;
     private final Staticness staticness;
     private final String actionName;
     private final ArtifactCategory linkerOutput;
     private final Picness picness;
+    private final Executable executable;
 
     LinkTargetType(
         String extension,
         Staticness staticness,
         String actionName,
         Picness picness,
-        ArtifactCategory linkerOutput) {
+        ArtifactCategory linkerOutput,
+        Executable executable) {
       this.extension = extension;
       this.staticness = staticness;
       this.actionName = actionName;
       this.linkerOutput = linkerOutput;
       this.picness = picness;
+      this.executable = executable;
     }
 
     /**
@@ -223,6 +256,11 @@ public abstract class Link {
     public String getActionName() {
       return actionName;
     }
+    
+    /** Returns true iff this link type is executable */
+    public boolean isExecutable() {
+      return (executable == Executable.EXECUTABLE);
+    }
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkCommandLine.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkCommandLine.java
index 27e3e4db99..6a95202423 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkCommandLine.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkCommandLine.java
@@ -408,6 +408,7 @@ public final class LinkCommandLine extends CommandLine {
         // TODO(b/30109612): make this pattern the case for all link variants.
       case OBJC_ARCHIVE:
       case OBJC_FULLY_LINKED_ARCHIVE:
+      case OBJC_EXECUTABLE:
         argv.add(toolPath);
         argv.addAll(featureConfiguration.getCommandLine(actionName, variables));
         break;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/BinaryLinkingTargetFactory.java b/src/main/java/com/google/devtools/build/lib/rules/objc/BinaryLinkingTargetFactory.java
index 59eddc2d90..ea26384486 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/BinaryLinkingTargetFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/BinaryLinkingTargetFactory.java
@@ -115,34 +115,26 @@ abstract class BinaryLinkingTargetFactory implements RuleConfiguredTargetFactory
             ruleContext.getPrerequisites("deps", Mode.TARGET, J2ObjcEntryClassProvider.class))
         .build();
 
-    CompilationSupport compilationSupport;
-    LegacyCompilationSupport legacyCompilationSupport = new LegacyCompilationSupport(ruleContext);
+    CompilationSupport compilationSupport = (usesCrosstool != UsesCrosstool.EXPERIMENTAL
+        || !ruleContext.getFragment(ObjcConfiguration.class).useCrosstoolForBinary())
+        ? new LegacyCompilationSupport(ruleContext)
+        : new CrosstoolCompilationSupport(ruleContext);
 
-    if (usesCrosstool != UsesCrosstool.EXPERIMENTAL
-        || !ruleContext.getFragment(ObjcConfiguration.class).useCrosstoolForBinary()) {
-      compilationSupport = legacyCompilationSupport;
-    } else {
-      compilationSupport = new CrosstoolCompilationSupport(ruleContext);
-    }
-     
     compilationSupport
+        .validateAttributes()
         .addXcodeSettings(xcodeProviderBuilder, common)
         .registerCompileAndArchiveActions(common)
         .registerFullyLinkAction(
             common.getObjcProvider(),
             ruleContext.getImplicitOutputArtifact(CompilationSupport.FULLY_LINKED_LIB))
-        .validateAttributes();
+        .registerLinkActions(
+            objcProvider,
+            j2ObjcMappingFileProvider,
+            j2ObjcEntryClassProvider,
+            getExtraLinkArgs(ruleContext),
+            ImmutableList.<Artifact>of(),
+            DsymOutputType.APP);
     
-    // TODO(b/29582284): Factor into the above if/else once CrosstoolCompilationSupport supports
-    // executable linking.
-    legacyCompilationSupport.registerLinkActions(
-        objcProvider,
-        j2ObjcMappingFileProvider,
-        j2ObjcEntryClassProvider,
-        getExtraLinkArgs(ruleContext),
-        ImmutableList.<Artifact>of(),
-        DsymOutputType.APP);
-
     Optional<XcTestAppProvider> xcTestAppProvider;
     Optional<RunfilesSupport> maybeRunfilesSupport = Optional.absent();
     switch (hasReleaseBundlingSupport) {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
index 8bf9121f19..aaa5d80f60 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
@@ -15,10 +15,15 @@
 package com.google.devtools.build.lib.rules.objc;
 
 import static com.google.devtools.build.lib.packages.ImplicitOutputsFunction.fromTemplates;
+import static com.google.devtools.build.lib.rules.cpp.Link.LINK_LIBRARY_FILETYPES;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FORCE_LOAD_LIBRARY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FRAMEWORK_DIR;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FRAMEWORK_SEARCH_PATH_ONLY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.IMPORTED_LIBRARY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.INCLUDE_SYSTEM;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LIBRARY;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_DYLIB;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_FRAMEWORK;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.COMPILABLE_SRCS_TYPE;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.HEADERS;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.NON_ARC_SRCS_TYPE;
@@ -28,7 +33,9 @@ import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.SWIFT_SOU
 import static java.nio.charset.StandardCharsets.ISO_8859_1;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Joiner;
 import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
 import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
@@ -67,8 +74,11 @@ import com.google.devtools.build.lib.rules.test.InstrumentedFilesCollector.Local
 import com.google.devtools.build.lib.rules.test.InstrumentedFilesProvider;
 import com.google.devtools.build.lib.util.FileTypeSet;
 import com.google.devtools.build.lib.util.Pair;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.PathFragment;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Support for rules that compile sources. Provides ways to determine files that should be output,
@@ -119,6 +129,17 @@ public abstract class CompilationSupport {
       ImmutableList.of(
           "-fexceptions", "-fasm-blocks", "-fobjc-abi-version=2", "-fobjc-legacy-dispatch");
 
+  private static final String FRAMEWORK_SUFFIX = ".framework";
+  
+  /** Selects cc libraries that have alwayslink=1. */
+  protected static final Predicate<Artifact> ALWAYS_LINKED_CC_LIBRARY =
+      new Predicate<Artifact>() {
+        @Override
+        public boolean apply(Artifact input) {
+          return LINK_LIBRARY_FILETYPES.matches(input.getFilename());
+        }
+      };
+  
   /**
    * Returns the location of the xcrunwrapper tool.
    */
@@ -427,7 +448,7 @@ public abstract class CompilationSupport {
         // The COVERAGE_GCOV_PATH environment variable is added in TestSupport#getExtraProviders()
         NestedSetBuilder.<Pair<String, String>>emptySet(Order.COMPILE_ORDER),
         !TargetUtils.isTestRule(ruleContext.getTarget()));
-  } 
+  }
 
   /**
    * Registers an action that will generate a clang module map for this target, using the hdrs
@@ -450,7 +471,7 @@ public abstract class CompilationSupport {
     return this;
   }
 
-   /**
+  /**
    * Validates compilation-related attributes on this rule.
    *
    * @return this compilation support
@@ -578,7 +599,7 @@ public abstract class CompilationSupport {
       J2ObjcEntryClassProvider j2ObjcEntryClassProvider,
       ExtraLinkArgs extraLinkArgs,
       Iterable<Artifact> extraLinkInputs,
-      DsymOutputType dsymOutputType);
+      DsymOutputType dsymOutputType) throws InterruptedException;
 
   /**
    * Returns the copts for the compile action in the current rule context (using a combination of
@@ -611,7 +632,7 @@ public abstract class CompilationSupport {
     }
     return copts;
   }
-  
+
   /**
    * Registers an action that writes given set of object files to the given objList. This objList is
    * suitable to signal symbols to archive in a libtool archiving invocation.
@@ -645,8 +666,8 @@ public abstract class CompilationSupport {
   }
  
   /**
-   * Registers an action to create an archive artifact by fully (statically) linking all
-   * transitive dependencies of this rule.
+   * Registers an action to create an archive artifact by fully (statically) linking all transitive
+   * dependencies of this rule.
    *
    * @param objcProvider provides all compiling and linking information to create this artifact
    * @param inputArtifacts inputs for this action
@@ -657,7 +678,200 @@ public abstract class CompilationSupport {
       ObjcProvider objcProvider, Iterable<Artifact> inputArtifacts, Artifact outputArchive)
       throws InterruptedException;
 
- 
+ /**
+   * Returns all framework names to pass to the linker using {@code -framework} flags. For a
+   * framework in the directory foo/bar.framework, the name is "bar". Each framework is found
+   * without using the full path by means of the framework search paths. Search paths are added by
+   * {@link#commonLinkAndCompileFlagsForClang(ObjcProvider, ObjcConfiguration, AppleConfiguration)})
+   *
+   * <p>It's awful that we can't pass the full path to the framework and avoid framework search
+   * paths, but this is imposed on us by clang. clang does not support passing the full path to the
+   * framework, so Bazel cannot do it either.
+   */
+  protected Set<String> frameworkNames(ObjcProvider provider) {
+    Set<String> names = new LinkedHashSet<>();
+    Iterables.addAll(names, SdkFramework.names(provider.get(SDK_FRAMEWORK)));
+    for (PathFragment frameworkDir : provider.get(FRAMEWORK_DIR)) {
+      String segment = frameworkDir.getBaseName();
+      Preconditions.checkState(
+          segment.endsWith(FRAMEWORK_SUFFIX),
+          "expect %s to end with %s, but it does not",
+          segment,
+          FRAMEWORK_SUFFIX);
+      names.add(segment.substring(0, segment.length() - FRAMEWORK_SUFFIX.length()));
+    }
+    return names;
+  }
+  
+  /**
+   * Returns libraries that should be passed to the linker.
+   */
+  protected ImmutableList<String> libraryNames(ObjcProvider objcProvider) {
+    ImmutableList.Builder<String> args = new ImmutableList.Builder<>();
+    for (String dylib : objcProvider.get(SDK_DYLIB)) {
+      if (dylib.startsWith("lib")) {
+        // remove lib prefix if it exists which is standard
+        // for libraries (libxml.dylib -> -lxml).
+        dylib = dylib.substring(3);
+      }
+      args.add(dylib);
+    }
+    return args.build();
+  }
+  
+  /**
+   * Returns libraries that should be passed into the linker with {@code -force_load}.
+   */
+  protected ImmutableSet<Artifact> getForceLoadArtifacts(ObjcProvider objcProvider) {
+    ImmutableList<Artifact> ccLibraries = objcProvider.getCcLibraries();
+    Iterable<Artifact> ccLibrariesToForceLoad =
+        Iterables.filter(ccLibraries, ALWAYS_LINKED_CC_LIBRARY);
+
+    return ImmutableSet.<Artifact>builder()
+        .addAll(objcProvider.get(FORCE_LOAD_LIBRARY))
+        .addAll(ccLibrariesToForceLoad)
+        .build();
+  }
+
+  /** Returns pruned J2Objc archives for this target. */
+  protected ImmutableList<Artifact> j2objcPrunedLibraries(ObjcProvider objcProvider) {
+    ImmutableList.Builder<Artifact> j2objcPrunedLibraryBuilder = ImmutableList.builder();
+    for (Artifact j2objcLibrary : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY)) {
+      j2objcPrunedLibraryBuilder.add(intermediateArtifacts.j2objcPrunedArchive(j2objcLibrary));
+    }
+    return j2objcPrunedLibraryBuilder.build();
+  }
+  
+  /**
+   * Returns true if this build should strip J2Objc dead code.
+   */
+  protected boolean stripJ2ObjcDeadCode(J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
+    J2ObjcConfiguration j2objcConfiguration =
+        buildConfiguration.getFragment(J2ObjcConfiguration.class);
+    // Only perform J2ObjC dead code stripping if flag --j2objc_dead_code_removal is specified and
+    // users have specified entry classes.
+    return j2objcConfiguration.removeDeadCode()
+        && !j2ObjcEntryClassProvider.getEntryClasses().isEmpty();
+  }
+
+  /**
+   * Registers actions to perform J2Objc dead code removal.
+   */
+  protected void registerJ2ObjcDeadCodeRemovalActions(
+      ObjcProvider objcProvider,
+      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
+      J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
+    NestedSet<String> entryClasses = j2ObjcEntryClassProvider.getEntryClasses();
+    Artifact pruner = ruleContext.getPrerequisiteArtifact("$j2objc_dead_code_pruner", Mode.HOST);
+    NestedSet<Artifact> j2ObjcDependencyMappingFiles =
+        j2ObjcMappingFileProvider.getDependencyMappingFiles();
+    NestedSet<Artifact> j2ObjcHeaderMappingFiles =
+        j2ObjcMappingFileProvider.getHeaderMappingFiles();
+    NestedSet<Artifact> j2ObjcArchiveSourceMappingFiles =
+        j2ObjcMappingFileProvider.getArchiveSourceMappingFiles();
+
+    for (Artifact j2objcArchive : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY)) {
+      PathFragment paramFilePath =
+          FileSystemUtils.replaceExtension(
+              j2objcArchive.getOwner().toPathFragment(), ".param.j2objc");
+      Artifact paramFile =
+          ruleContext.getUniqueDirectoryArtifact(
+              "_j2objc_pruned", paramFilePath, ruleContext.getBinOrGenfilesDirectory());
+      Artifact prunedJ2ObjcArchive = intermediateArtifacts.j2objcPrunedArchive(j2objcArchive);
+      Artifact dummyArchive =
+          Iterables.getOnlyElement(
+              ruleContext
+                  .getPrerequisite("$dummy_lib", Mode.TARGET, ObjcProvider.class)
+                  .get(LIBRARY));
+
+      CustomCommandLine commandLine =
+          CustomCommandLine.builder()
+              .addExecPath("--input_archive", j2objcArchive)
+              .addExecPath("--output_archive", prunedJ2ObjcArchive)
+              .addExecPath("--dummy_archive", dummyArchive)
+              .addExecPath("--xcrunwrapper", xcrunwrapper(ruleContext).getExecutable())
+              .addJoinExecPaths("--dependency_mapping_files", ",", j2ObjcDependencyMappingFiles)
+              .addJoinExecPaths("--header_mapping_files", ",", j2ObjcHeaderMappingFiles)
+              .addJoinExecPaths(
+                  "--archive_source_mapping_files", ",", j2ObjcArchiveSourceMappingFiles)
+              .add("--entry_classes")
+              .add(Joiner.on(",").join(entryClasses))
+              .build();
+
+      ruleContext.registerAction(
+          new ParameterFileWriteAction(
+              ruleContext.getActionOwner(),
+              paramFile,
+              commandLine,
+              ParameterFile.ParameterFileType.UNQUOTED,
+              ISO_8859_1));
+      ruleContext.registerAction(
+          ObjcRuleClasses.spawnAppleEnvActionBuilder(
+                  appleConfiguration, appleConfiguration.getSingleArchPlatform())
+              .setMnemonic("DummyPruner")
+              .setExecutable(pruner)
+              .addInput(dummyArchive)
+              .addInput(pruner)
+              .addInput(paramFile)
+              .addInput(j2objcArchive)
+              .addInput(xcrunwrapper(ruleContext).getExecutable())
+              .addTransitiveInputs(j2ObjcDependencyMappingFiles)
+              .addTransitiveInputs(j2ObjcHeaderMappingFiles)
+              .addTransitiveInputs(j2ObjcArchiveSourceMappingFiles)
+              .setCommandLine(
+                  CustomCommandLine.builder().addPaths("@%s", paramFile.getExecPath()).build())
+              .addOutput(prunedJ2ObjcArchive)
+              .build(ruleContext));
+    }
+  }
+  
+  /** Returns archives arising from j2objc transpilation after dead code removal. */
+  protected Iterable<Artifact> computeAndStripPrunedJ2ObjcArchives(
+      J2ObjcEntryClassProvider j2ObjcEntryClassProvider,
+      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
+      ObjcProvider objcProvider) {
+    Iterable<Artifact> prunedJ2ObjcArchives = ImmutableList.<Artifact>of();
+    if (stripJ2ObjcDeadCode(j2ObjcEntryClassProvider)) {
+      registerJ2ObjcDeadCodeRemovalActions(
+          objcProvider, j2ObjcMappingFileProvider, j2ObjcEntryClassProvider);
+      prunedJ2ObjcArchives = j2objcPrunedLibraries(objcProvider);
+    }
+    return prunedJ2ObjcArchives;
+  }
+
+  /**
+   * Returns a nested set of Bazel-built ObjC libraries with all unpruned J2ObjC libraries
+   * substituted with pruned ones.
+   */
+  protected ImmutableList<Artifact> substituteJ2ObjcPrunedLibraries(ObjcProvider objcProvider) {
+    ImmutableList.Builder<Artifact> libraries = new ImmutableList.Builder<>();
+
+    Set<Artifact> unprunedJ2ObjcLibs = objcProvider.get(ObjcProvider.J2OBJC_LIBRARY).toSet();
+    for (Artifact library : objcProvider.getObjcLibraries()) {
+      // If we match an unpruned J2ObjC library, add the pruned version of the J2ObjC static library
+      // instead.
+      if (unprunedJ2ObjcLibs.contains(library)) {
+        libraries.add(intermediateArtifacts.j2objcPrunedArchive(library));
+      } else {
+        libraries.add(library);
+      }
+    }
+    return libraries.build();
+  }
+  
+  /** Returns the artifact that should be the outcome of this build's link action */
+  protected Artifact getBinaryToLink() {
+
+    // When compilation_mode=opt and objc_enable_binary_stripping are specified, the unstripped
+    // binary containing debug symbols is generated by the linker, which also needs the debug
+    // symbols for dead-code removal. The binary is also used to generate dSYM bundle if
+    // --apple_generate_dsym is specified. A symbol strip action is later registered to strip
+    // the symbol table from the unstripped binary.
+    return objcConfiguration.shouldStripBinary()
+        ? intermediateArtifacts.unstrippedSingleArchitectureBinary()
+        : intermediateArtifacts.strippedSingleArchitectureBinary();    
+  }
+
   private NestedSet<Artifact> getGcovForObjectiveCIfNeeded() {
     if (ruleContext.getConfiguration().isCodeCoverageEnabled()
         && ruleContext.attributes().has(IosTest.OBJC_GCOV_ATTR, BuildType.LABEL)) {
@@ -719,4 +933,4 @@ public abstract class CompilationSupport {
     }
     return parents.build();
   }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/CrosstoolCompilationSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/CrosstoolCompilationSupport.java
index bf50ddff16..cd6789d3d1 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/CrosstoolCompilationSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/CrosstoolCompilationSupport.java
@@ -15,12 +15,17 @@
 package com.google.devtools.build.lib.rules.objc;
 
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.DEFINE;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.DYNAMIC_FRAMEWORK_FILE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.IMPORTED_LIBRARY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.INCLUDE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.INCLUDE_SYSTEM;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.STATIC_FRAMEWORK_FILE;
 
+import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
@@ -38,15 +43,16 @@ import com.google.devtools.build.lib.rules.cpp.CppRuleClasses;
 import com.google.devtools.build.lib.rules.cpp.Link.LinkStaticness;
 import com.google.devtools.build.lib.rules.cpp.Link.LinkTargetType;
 import com.google.devtools.build.lib.rules.cpp.PrecompiledFiles;
+import com.google.devtools.build.lib.rules.objc.ObjcVariablesExtension.VariableCategory;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import java.util.Collection;
 
 /**
- * Constructs command lines for objc compilation, archiving, and linking.  Uses the crosstool
- * infrastructure to register {@link CppCompileAction} and {@link CppLinkAction} instances,
- * making use of a provided toolchain.
- * 
- * TODO(b/28403953): Deprecate LegacyCompilationSupport in favor of this implementation for all
+ * Constructs command lines for objc compilation, archiving, and linking. Uses the crosstool
+ * infrastructure to register {@link CppCompileAction} and {@link CppLinkAction} instances, making
+ * use of a provided toolchain.
+ *
+ * <p>TODO(b/28403953): Deprecate LegacyCompilationSupport in favor of this implementation for all
  * objc rules.
  */
 public class CrosstoolCompilationSupport extends CompilationSupport {
@@ -59,6 +65,7 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
           "objc++-compile",
           "objc-archive",
           "objc-fully-link",
+          "objc-executable",
           "assemble",
           "preprocess-assemble",
           "c-compile",
@@ -79,25 +86,37 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
         CompilationAttributes.Builder.fromRuleContext(ruleContext).build());
     this.compilationArtifacts = compilationArtifacts(ruleContext);
   }
-
+ 
   @Override
   CompilationSupport registerCompileAndArchiveActions(
       ObjcCommon common, ExtraCompileArgs extraCompileArgs, Iterable<PathFragment> priorityHeaders)
       throws RuleErrorException, InterruptedException {
 
-    CcLibraryHelper helper = createCcLibraryHelper(common);
-
+    ObjcVariablesExtension.Builder extension = new ObjcVariablesExtension.Builder()
+        .setRuleContext(ruleContext)
+        .setObjcProvider(common.getObjcProvider())
+        .setCompilationArtifacts(compilationArtifacts)
+        .setIntermediateArtifacts(intermediateArtifacts)
+        .setConfiguration(ruleContext.getConfiguration());
+    CcLibraryHelper helper;
+    
     if (compilationArtifacts.getArchive().isPresent()) {
       Artifact objList = intermediateArtifacts.archiveObjList();
 
       // TODO(b/30783125): Signal the need for this action in the CROSSTOOL.
       registerObjFilelistAction(getObjFiles(compilationArtifacts, intermediateArtifacts), objList);
 
-      helper.setLinkType(LinkTargetType.OBJC_ARCHIVE).addLinkActionInput(objList);
+      extension.addVariableCategory(VariableCategory.ARCHIVE_VARIABLES);
+      
+      helper = createCcLibraryHelper(common, extension.build())
+          .setLinkType(LinkTargetType.OBJC_ARCHIVE)
+          .addLinkActionInput(objList);
+    } else {
+      helper = createCcLibraryHelper(common, extension.build());
     }
-
-    helper.build();
     
+    helper.build();
+
     return this;
   }
 
@@ -113,6 +132,16 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
             .getPackageDirectory()
             .getRelative(labelName.replaceName("lib" + labelName.getBaseName()))
             .getPathString();
+    ObjcVariablesExtension extension = new ObjcVariablesExtension.Builder()
+        .setRuleContext(ruleContext)
+        .setObjcProvider(objcProvider)
+        .setConfiguration(ruleContext.getConfiguration())
+        .setIntermediateArtifacts(intermediateArtifacts)
+        .setFullyLinkArchive(
+            ruleContext.getImplicitOutputArtifact(CompilationSupport.FULLY_LINKED_LIB))
+        .addVariableCategory(VariableCategory.FULLY_LINK_VARIABLES)
+        .build();
+    
     CppLinkAction fullyLinkAction =
         new CppLinkActionBuilder(ruleContext, fullyLinkedArchive)
             .addActionInputs(objcProvider.getObjcLibraries())
@@ -121,7 +150,7 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
             .setLinkType(LinkTargetType.OBJC_FULLY_LINKED_ARCHIVE)
             .setLinkStaticness(LinkStaticness.FULLY_STATIC)
             .setLibraryIdentifier(libraryIdentifier)
-            .addVariablesExtension(getVariablesExtension(objcProvider))
+            .addVariablesExtension(extension)
             .setFeatureConfiguration(getFeatureConfiguration(ruleContext))
             .build();
     ruleContext.registerAction(fullyLinkAction);
@@ -136,12 +165,61 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
       J2ObjcEntryClassProvider j2ObjcEntryClassProvider,
       ExtraLinkArgs extraLinkArgs,
       Iterable<Artifact> extraLinkInputs,
-      DsymOutputType dsymOutputType) {
-    // TODO(b/29582284): Implement the link action in the objc crosstool.
-    throw new UnsupportedOperationException();
+      DsymOutputType dsymOutputType) throws InterruptedException {
+    Iterable<Artifact> prunedJ2ObjcArchives =
+        computeAndStripPrunedJ2ObjcArchives(
+            j2ObjcEntryClassProvider, j2ObjcMappingFileProvider, objcProvider);
+    ImmutableList<Artifact> bazelBuiltLibraries =
+        Iterables.isEmpty(prunedJ2ObjcArchives)
+            ? objcProvider.getObjcLibraries()
+            : substituteJ2ObjcPrunedLibraries(objcProvider);
+
+    Artifact inputFileList = intermediateArtifacts.linkerObjList();
+    ImmutableSet<Artifact> forceLinkArtifacts = getForceLoadArtifacts(objcProvider);
+
+    Iterable<Artifact> objFiles =
+        Iterables.concat(
+            bazelBuiltLibraries, objcProvider.get(IMPORTED_LIBRARY), objcProvider.getCcLibraries());
+    // Clang loads archives specified in filelists and also specified as -force_load twice,
+    // resulting in duplicate symbol errors unless they are deduped.
+    objFiles = Iterables.filter(objFiles, Predicates.not(Predicates.in(forceLinkArtifacts)));
+
+    registerObjFilelistAction(objFiles, inputFileList);
+
+    ObjcVariablesExtension extension = new ObjcVariablesExtension.Builder()
+        .setRuleContext(ruleContext)
+        .setObjcProvider(objcProvider)
+        .setConfiguration(ruleContext.getConfiguration())
+        .setIntermediateArtifacts(intermediateArtifacts)
+        .setFrameworkNames(frameworkNames(objcProvider))
+        .setLibraryNames(libraryNames(objcProvider))
+        .setForceLoadArtifacts(getForceLoadArtifacts(objcProvider))
+        .setAttributeLinkopts(attributes.linkopts())
+        .addVariableCategory(VariableCategory.EXECUTABLE_LINKING_VARIABLES)
+        .build();
+    
+    Artifact binaryToLink = getBinaryToLink();
+    CppLinkAction executableLinkAction =
+        new CppLinkActionBuilder(ruleContext, binaryToLink)
+            .setMnemonic("ObjcLink")
+            .addActionInputs(bazelBuiltLibraries)
+            .addActionInputs(objcProvider.getCcLibraries())
+            .addTransitiveActionInputs(objcProvider.get(IMPORTED_LIBRARY))
+            .addTransitiveActionInputs(objcProvider.get(STATIC_FRAMEWORK_FILE))
+            .addTransitiveActionInputs(objcProvider.get(DYNAMIC_FRAMEWORK_FILE))
+            .addActionInputs(prunedJ2ObjcArchives)
+            .addActionInput(inputFileList)
+            .setLinkType(LinkTargetType.OBJC_EXECUTABLE)
+            .setLinkStaticness(LinkStaticness.FULLY_STATIC)
+            .addVariablesExtension(extension)
+            .setFeatureConfiguration(getFeatureConfiguration(ruleContext))
+            .build();
+    ruleContext.registerAction(executableLinkAction);    
+    
+    return this;
   }
 
-  private CcLibraryHelper createCcLibraryHelper(ObjcCommon common) throws InterruptedException {
+  private CcLibraryHelper createCcLibraryHelper(ObjcCommon common, VariablesExtension extension) {
     PrecompiledFiles precompiledFiles = new PrecompiledFiles(ruleContext);
     Collection<Artifact> arcSources = Sets.newHashSet(compilationArtifacts.getSrcs());
     Collection<Artifact> nonArcSources = Sets.newHashSet(compilationArtifacts.getNonArcSrcs());
@@ -170,7 +248,7 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
         .addCopts(ruleContext.getFragment(ObjcConfiguration.class).getCoptsForCompilationMode())
         .addSystemIncludeDirs(common.getObjcProvider().get(INCLUDE_SYSTEM))
         .setCppModuleMap(intermediateArtifacts.moduleMap())
-        .addVariableExtension(getVariablesExtension(common.getObjcProvider()));
+        .addVariableExtension(extension);
   }
 
   private static FeatureConfiguration getFeatureConfiguration(RuleContext ruleContext) {
@@ -192,7 +270,7 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
             .add(CppRuleClasses.COMPILE_ACTION_FLAGS_IN_FLAG_SET)
             .add(CppRuleClasses.DEPENDENCY_FILE)
             .add(CppRuleClasses.INCLUDE_PATHS);
-    
+
     if (ruleContext.getConfiguration().getFragment(ObjcConfiguration.class).moduleMapsEnabled()) {
       activatedCrosstoolSelectables.add(OBJC_MODULE_FEATURE_NAME);
     }
@@ -207,17 +285,6 @@ public class CrosstoolCompilationSupport extends CompilationSupport {
     return toolchain.getFeatures().getFeatureConfiguration(activatedCrosstoolSelectables.build());
   }
 
-  private VariablesExtension getVariablesExtension(ObjcProvider objcProvider)
-      throws InterruptedException {
-    return new ObjcVariablesExtension(
-        ruleContext,
-        objcProvider,
-        compilationArtifacts,
-        ruleContext.getImplicitOutputArtifact(CompilationSupport.FULLY_LINKED_LIB),
-        intermediateArtifacts,
-        ruleContext.getConfiguration());
-  }
-
   private static ImmutableList<Artifact> getObjFiles(
       CompilationArtifacts compilationArtifacts, IntermediateArtifacts intermediateArtifacts) {
     ImmutableList.Builder<Artifact> result = new ImmutableList.Builder<>();
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/LegacyCompilationSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/LegacyCompilationSupport.java
index f7fdcdfb62..4658c5bd15 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/LegacyCompilationSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/LegacyCompilationSupport.java
@@ -14,22 +14,17 @@
 
 package com.google.devtools.build.lib.rules.objc;
 
-import static com.google.devtools.build.lib.rules.cpp.Link.LINK_LIBRARY_FILETYPES;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.DEFINE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.DYNAMIC_FRAMEWORK_FILE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FORCE_LOAD_LIBRARY;
-import static com.google.devtools.build.lib.rules.objc.ObjcProvider.FRAMEWORK_DIR;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.Flag.USES_CPP;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.Flag.USES_SWIFT;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.HEADER;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.IMPORTED_LIBRARY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.INCLUDE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.INCLUDE_SYSTEM;
-import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LIBRARY;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LINK_INPUTS;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.MODULE_MAP;
-import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_DYLIB;
-import static com.google.devtools.build.lib.rules.objc.ObjcProvider.SDK_FRAMEWORK;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.STATIC_FRAMEWORK_FILE;
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.WEAK_SDK_FRAMEWORK;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.CLANG;
@@ -42,24 +37,20 @@ import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.PRECOMPIL
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.SRCS_TYPE;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.STRIP;
 import static com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.SWIFT;
-import static java.nio.charset.StandardCharsets.ISO_8859_1;
 
 import com.google.common.base.Joiner;
 import com.google.common.base.Optional;
-import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
-import com.google.devtools.build.lib.actions.ParameterFile;
 import com.google.devtools.build.lib.analysis.PrerequisiteArtifacts;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.actions.CommandLine;
 import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
-import com.google.devtools.build.lib.analysis.actions.ParameterFileWriteAction;
 import com.google.devtools.build.lib.analysis.actions.SpawnAction;
 import com.google.devtools.build.lib.analysis.actions.SpawnActionTemplate;
 import com.google.devtools.build.lib.analysis.actions.SpawnActionTemplate.OutputPathMapper;
@@ -77,9 +68,7 @@ import com.google.devtools.build.lib.rules.cpp.CppModuleMap;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.PathFragment;
-import java.util.ArrayList;
 import java.util.List;
-import java.util.Set;
 
 /**
  * Constructs command lines for objc compilation, archiving, and linking.  Uses hard-coded
@@ -89,17 +78,6 @@ import java.util.Set;
  */
 public class LegacyCompilationSupport extends CompilationSupport {
 
-  private static final String FRAMEWORK_SUFFIX = ".framework";
-
-  /** Selects cc libraries that have alwayslink=1. */
-  private static final Predicate<Artifact> ALWAYS_LINKED_CC_LIBRARY =
-      new Predicate<Artifact>() {
-        @Override
-        public boolean apply(Artifact input) {
-          return LINK_LIBRARY_FILETYPES.matches(input.getFilename());
-        }
-      };
-
   /**
    * A mapper that maps input ObjC source {@link Artifact.TreeFileArtifact}s to output object file
    * {@link Artifact.TreeFileArtifact}s.
@@ -798,12 +776,9 @@ public class LegacyCompilationSupport extends CompilationSupport {
       dsymBundleZip = Optional.absent();
     }
 
-    Iterable<Artifact> prunedJ2ObjcArchives = ImmutableList.<Artifact>of();
-    if (stripJ2ObjcDeadCode(j2ObjcEntryClassProvider)) {
-      registerJ2ObjcDeadCodeRemovalActions(objcProvider, j2ObjcMappingFileProvider,
-          j2ObjcEntryClassProvider);
-      prunedJ2ObjcArchives = j2objcPrunedLibraries(objcProvider);
-    }
+    Iterable<Artifact> prunedJ2ObjcArchives =
+        computeAndStripPrunedJ2ObjcArchives(
+            j2ObjcEntryClassProvider, j2ObjcMappingFileProvider, objcProvider);
 
     if (objcConfiguration.generateLinkmap()) {
       linkmap = Optional.of(intermediateArtifacts.linkmap());
@@ -821,15 +796,6 @@ public class LegacyCompilationSupport extends CompilationSupport {
     return this;
   }
 
-  private boolean stripJ2ObjcDeadCode(J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
-    J2ObjcConfiguration j2objcConfiguration =
-        buildConfiguration.getFragment(J2ObjcConfiguration.class);
-    // Only perform J2ObjC dead code stripping if flag --j2objc_dead_code_removal is specified and
-    // users have specified entry classes.
-    return j2objcConfiguration.removeDeadCode()
-        && !j2ObjcEntryClassProvider.getEntryClasses().isEmpty();
-  }
-
   private boolean isDynamicLib(CommandLine commandLine) {
     return Iterables.contains(commandLine.arguments(), "-dynamiclib");
   }
@@ -841,15 +807,7 @@ public class LegacyCompilationSupport extends CompilationSupport {
       Optional<Artifact> dsymBundleZip,
       Iterable<Artifact> prunedJ2ObjcArchives,
       Optional<Artifact> linkmap) {
-    // When compilation_mode=opt and objc_enable_binary_stripping are specified, the unstripped
-    // binary containing debug symbols is generated by the linker, which also needs the debug
-    // symbols for dead-code removal. The binary is also used to generate dSYM bundle if
-    // --apple_generate_dsym is specified. A symbol strip action is later registered to strip
-    // the symbol table from the unstripped binary.
-    Artifact binaryToLink =
-        objcConfiguration.shouldStripBinary()
-            ? intermediateArtifacts.unstrippedSingleArchitectureBinary()
-            : intermediateArtifacts.strippedSingleArchitectureBinary();
+    Artifact binaryToLink = getBinaryToLink();
 
     ImmutableList<Artifact> objcLibraries = objcProvider.getObjcLibraries();
     ImmutableList<Artifact> ccLibraries = objcProvider.getCcLibraries();
@@ -912,14 +870,6 @@ public class LegacyCompilationSupport extends CompilationSupport {
     }
   }
 
-  private ImmutableList<Artifact> j2objcPrunedLibraries(ObjcProvider objcProvider) {
-    ImmutableList.Builder<Artifact> j2objcPrunedLibraryBuilder = ImmutableList.builder();
-    for (Artifact j2objcLibrary : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY)) {
-      j2objcPrunedLibraryBuilder.add(intermediateArtifacts.j2objcPrunedArchive(j2objcLibrary));
-    }
-    return j2objcPrunedLibraryBuilder.build();
-  }
-
   private static CommandLine symbolStripCommandLine(
       Iterable<String> extraFlags, Artifact unstrippedArtifact, Artifact strippedArtifact) {
     return CustomCommandLine.builder()
@@ -930,26 +880,6 @@ public class LegacyCompilationSupport extends CompilationSupport {
         .build();
   }
 
-  /**
-   * Returns a nested set of Bazel-built ObjC libraries with all unpruned J2ObjC libraries
-   * substituted with pruned ones.
-   */
-  private ImmutableList<Artifact> substituteJ2ObjcPrunedLibraries(ObjcProvider objcProvider) {
-    ImmutableList.Builder<Artifact> libraries = new ImmutableList.Builder<>();
-
-    Set<Artifact> unprunedJ2ObjcLibs = objcProvider.get(ObjcProvider.J2OBJC_LIBRARY).toSet();
-    for (Artifact library : objcProvider.getObjcLibraries()) {
-      // If we match an unpruned J2ObjC library, add the pruned version of the J2ObjC static library
-      // instead.
-      if (unprunedJ2ObjcLibs.contains(library)) {
-        libraries.add(intermediateArtifacts.j2objcPrunedArchive(library));
-      } else {
-        libraries.add(library);
-      }
-    }
-    return libraries.build();
-  }
-
   private CommandLine linkCommandLine(
       ExtraLinkArgs extraLinkArgs,
       ObjcProvider objcProvider,
@@ -1103,104 +1033,6 @@ public class LegacyCompilationSupport extends CompilationSupport {
     }
   }
 
-  private Iterable<String> libraryNames(ObjcProvider objcProvider) {
-    ImmutableList.Builder<String> args = new ImmutableList.Builder<>();
-    for (String dylib : objcProvider.get(SDK_DYLIB)) {
-      if (dylib.startsWith("lib")) {
-        // remove lib prefix if it exists which is standard
-        // for libraries (libxml.dylib -> -lxml).
-        dylib = dylib.substring(3);
-      }
-      args.add(dylib);
-    }
-    return args.build();
-  }
-
-  /**
-   * All framework names to pass to the linker using {@code -framework} flags. For a framework in
-   * the directory foo/bar.framework, the name is "bar". Each framework is found without using the
-   * full path by means of the framework search paths. The search paths are added by
-   * {@link #commonLinkAndCompileFlagsForClang(ObjcProvider, ObjcConfiguration,
-   * AppleConfiguration)}).
-   *
-   * <p>It's awful that we can't pass the full path to the framework and avoid framework search
-   * paths, but this is imposed on us by clang. clang does not support passing the full path to the
-   * framework, so Bazel cannot do it either.
-   */
-  private Iterable<String> frameworkNames(ObjcProvider provider) {
-    List<String> names = new ArrayList<>();
-    Iterables.addAll(names, SdkFramework.names(provider.get(SDK_FRAMEWORK)));
-    for (PathFragment frameworkDir : provider.get(FRAMEWORK_DIR)) {
-      String segment = frameworkDir.getBaseName();
-      Preconditions.checkState(segment.endsWith(FRAMEWORK_SUFFIX),
-          "expect %s to end with %s, but it does not", segment, FRAMEWORK_SUFFIX);
-      names.add(segment.substring(0, segment.length() - FRAMEWORK_SUFFIX.length()));
-    }
-    return names;
-  }
-
-  private void registerJ2ObjcDeadCodeRemovalActions(ObjcProvider objcProvider,
-      J2ObjcMappingFileProvider j2ObjcMappingFileProvider,
-      J2ObjcEntryClassProvider j2ObjcEntryClassProvider) {
-    NestedSet<String> entryClasses = j2ObjcEntryClassProvider.getEntryClasses();
-    Artifact pruner = ruleContext.getPrerequisiteArtifact("$j2objc_dead_code_pruner", Mode.HOST);
-    NestedSet<Artifact> j2ObjcDependencyMappingFiles =
-        j2ObjcMappingFileProvider.getDependencyMappingFiles();
-    NestedSet<Artifact> j2ObjcHeaderMappingFiles =
-        j2ObjcMappingFileProvider.getHeaderMappingFiles();
-    NestedSet<Artifact> j2ObjcArchiveSourceMappingFiles =
-        j2ObjcMappingFileProvider.getArchiveSourceMappingFiles();
-
-    for (Artifact j2objcArchive : objcProvider.get(ObjcProvider.J2OBJC_LIBRARY)) {
-      PathFragment paramFilePath = FileSystemUtils.replaceExtension(
-          j2objcArchive.getOwner().toPathFragment(), ".param.j2objc");
-      Artifact paramFile = ruleContext.getUniqueDirectoryArtifact(
-          "_j2objc_pruned",
-          paramFilePath,
-          ruleContext.getBinOrGenfilesDirectory());
-      Artifact prunedJ2ObjcArchive = intermediateArtifacts.j2objcPrunedArchive(j2objcArchive);
-      Artifact dummyArchive = Iterables.getOnlyElement(
-          ruleContext.getPrerequisite("$dummy_lib", Mode.TARGET, ObjcProvider.class)
-          .get(LIBRARY));
-
-      CustomCommandLine commandLine = CustomCommandLine.builder()
-          .addExecPath("--input_archive", j2objcArchive)
-          .addExecPath("--output_archive", prunedJ2ObjcArchive)
-          .addExecPath("--dummy_archive", dummyArchive)
-          .addExecPath("--xcrunwrapper", xcrunwrapper(ruleContext).getExecutable())
-          .addJoinExecPaths("--dependency_mapping_files", ",", j2ObjcDependencyMappingFiles)
-          .addJoinExecPaths("--header_mapping_files", ",", j2ObjcHeaderMappingFiles)
-          .addJoinExecPaths(
-              "--archive_source_mapping_files", ",", j2ObjcArchiveSourceMappingFiles)
-          .add("--entry_classes").add(Joiner.on(",").join(entryClasses))
-          .build();
-
-      ruleContext.registerAction(
-          new ParameterFileWriteAction(
-              ruleContext.getActionOwner(),
-              paramFile,
-              commandLine,
-              ParameterFile.ParameterFileType.UNQUOTED, ISO_8859_1));
-      ruleContext.registerAction(ObjcRuleClasses.spawnAppleEnvActionBuilder(
-                  appleConfiguration, appleConfiguration.getSingleArchPlatform())
-          .setMnemonic("DummyPruner")
-          .setExecutable(pruner)
-          .addInput(dummyArchive)
-          .addInput(pruner)
-          .addInput(paramFile)
-          .addInput(j2objcArchive)
-          .addInput(xcrunwrapper(ruleContext).getExecutable())
-          .addTransitiveInputs(j2ObjcDependencyMappingFiles)
-          .addTransitiveInputs(j2ObjcHeaderMappingFiles)
-          .addTransitiveInputs(j2ObjcArchiveSourceMappingFiles)
-          .setCommandLine(CustomCommandLine.builder()
-              .addPaths("@%s", paramFile.getExecPath())
-              .build())
-          .addOutput(prunedJ2ObjcArchive)
-          .build(ruleContext));
-      }
-  }
-
   private CompilationSupport registerDsymActions(DsymOutputType dsymOutputType) {
     Artifact tempDsymBundleZip = intermediateArtifacts.tempDsymBundleZip(dsymOutputType);
     Artifact linkedBinary =
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcVariablesExtension.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcVariablesExtension.java
index e14be86eba..851af8d32e 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcVariablesExtension.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcVariablesExtension.java
@@ -15,17 +15,22 @@
 package com.google.devtools.build.lib.rules.objc;
 
 import static com.google.devtools.build.lib.rules.objc.ObjcProvider.IMPORTED_LIBRARY;
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.LINKOPT;
 
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
 import com.google.devtools.build.lib.rules.apple.Platform;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.Variables.StringSequence;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.Variables.VariablesExtension;
+import java.util.Set;
 
 /** Build variable extensions for templating a toolchain for objc builds. */
 class ObjcVariablesExtension implements VariablesExtension {
@@ -43,22 +48,41 @@ class ObjcVariablesExtension implements VariablesExtension {
   static final String CC_LIBRARY_EXEC_PATHS_VARIABLE_NAME = "cc_library_exec_paths";
   static final String IMPORTED_LIBRARY_EXEC_PATHS_VARIABLE_NAME = "imported_library_exec_paths";
 
+  // executable linking variables
+  static final String FRAMEWORK_NAMES_VARIABLE_NAME = "framework_names";
+  static final String WEAK_FRAMEWORK_NAMES_VARIABLE_NAME = "weak_framework_names";
+  static final String LIBRARY_NAMES_VARIABLE_NAME = "library_names";
+  static final String FILELIST_VARIABLE_NAME = "filelist";
+  static final String LINKED_BINARY_VARIABLE_NAME = "linked_binary";
+  static final String FORCE_LOAD_EXEC_PATHS_VARIABLE_NAME = "force_load_exec_paths";
+  static final String DEP_LINKOPTS_VARIABLE_NAME = "dep_linkopts";
+  static final String ATTR_LINKOPTS_VARIABLE_NAME = "attr_linkopts";
+  
   private final RuleContext ruleContext;
   private final ObjcProvider objcProvider;
   private final CompilationArtifacts compilationArtifacts;
   private final Artifact fullyLinkArchive;
   private final IntermediateArtifacts intermediateArtifacts;
-
   private final BuildConfiguration buildConfiguration;
   private final AppleConfiguration appleConfiguration;
+  private final Set<String> frameworkNames;
+  private final ImmutableList<String> libraryNames;
+  private final ImmutableSet<Artifact> forceLoadArtifacts;
+  private final NestedSet<String> attributeLinkopts;
+  private final ImmutableSet<VariableCategory> activeVariableCategories;
 
-  public ObjcVariablesExtension(
+  private ObjcVariablesExtension(
       RuleContext ruleContext,
       ObjcProvider objcProvider,
       CompilationArtifacts compilationArtifacts,
       Artifact fullyLinkArchive,
       IntermediateArtifacts intermediateArtifacts,
-      BuildConfiguration buildConfiguration) {
+      BuildConfiguration buildConfiguration,
+      Set<String> frameworkNames,
+      ImmutableList<String> libraryNames,
+      ImmutableSet<Artifact> forceLoadArtifacts,
+      NestedSet<String> attributeLinkopts,
+      ImmutableSet<VariableCategory> activeVariableCategories) {
     this.ruleContext = ruleContext;
     this.objcProvider = objcProvider;
     this.compilationArtifacts = compilationArtifacts;
@@ -66,6 +90,16 @@ class ObjcVariablesExtension implements VariablesExtension {
     this.intermediateArtifacts = intermediateArtifacts;
     this.buildConfiguration = buildConfiguration;
     this.appleConfiguration = buildConfiguration.getFragment(AppleConfiguration.class);
+    this.frameworkNames = frameworkNames;
+    this.libraryNames = libraryNames;
+    this.forceLoadArtifacts = forceLoadArtifacts;
+    this.attributeLinkopts = attributeLinkopts;
+    this.activeVariableCategories = activeVariableCategories;
+  }
+
+  /** Type of build variable that can optionally exported by this extension. */
+  public enum VariableCategory {
+    ARCHIVE_VARIABLES, FULLY_LINK_VARIABLES, EXECUTABLE_LINKING_VARIABLES;
   }
 
   @Override
@@ -74,10 +108,15 @@ class ObjcVariablesExtension implements VariablesExtension {
     addFrameworkVariables(builder);
     addArchVariables(builder);
     addModuleMapVariables(builder);
-    if (compilationArtifacts.getArchive().isPresent()) {
+    if (activeVariableCategories.contains(VariableCategory.ARCHIVE_VARIABLES)) {
       addArchiveVariables(builder);
     }
-    addFullyLinkArchiveVariables(builder);
+    if (activeVariableCategories.contains(VariableCategory.FULLY_LINK_VARIABLES)) {
+      addFullyLinkArchiveVariables(builder);
+    }
+    if (activeVariableCategories.contains(VariableCategory.EXECUTABLE_LINKING_VARIABLES)) {
+      addExecutableLinkVariables(builder);
+    }
   }
 
   private void addPchVariables(CcToolchainFeatures.Variables.Builder builder) {
@@ -138,4 +177,144 @@ class ObjcVariablesExtension implements VariablesExtension {
         IMPORTED_LIBRARY_EXEC_PATHS_VARIABLE_NAME,
         ImmutableList.copyOf(Artifact.toExecPaths(objcProvider.get(IMPORTED_LIBRARY))));
   }
+
+  private void addExecutableLinkVariables(CcToolchainFeatures.Variables.Builder builder) {
+    builder.addSequenceVariable(FRAMEWORK_NAMES_VARIABLE_NAME, frameworkNames);
+    builder.addSequenceVariable(
+        WEAK_FRAMEWORK_NAMES_VARIABLE_NAME,
+        SdkFramework.names(objcProvider.get(ObjcProvider.WEAK_SDK_FRAMEWORK)));
+    builder.addSequenceVariable(LIBRARY_NAMES_VARIABLE_NAME, libraryNames);
+    builder.addVariable(
+        FILELIST_VARIABLE_NAME, intermediateArtifacts.linkerObjList().getExecPathString());
+    builder.addVariable(
+        LINKED_BINARY_VARIABLE_NAME,
+        ruleContext.getFragment(ObjcConfiguration.class).shouldStripBinary()
+            ? intermediateArtifacts.unstrippedSingleArchitectureBinary().getExecPathString()
+            : intermediateArtifacts.strippedSingleArchitectureBinary().getExecPathString());
+
+    builder.addSequenceVariable(
+        FORCE_LOAD_EXEC_PATHS_VARIABLE_NAME,
+        Artifact.toExecPaths(forceLoadArtifacts));
+    builder.addSequenceVariable(DEP_LINKOPTS_VARIABLE_NAME, objcProvider.get(LINKOPT));
+    builder.addSequenceVariable(ATTR_LINKOPTS_VARIABLE_NAME, attributeLinkopts);
+  }
+
+  /** A Builder for {@link ObjcVariablesExtension}. */
+  static class Builder {
+    private RuleContext ruleContext;
+    private ObjcProvider objcProvider;
+    private CompilationArtifacts compilationArtifacts;
+    private Artifact fullyLinkArchive;
+    private IntermediateArtifacts intermediateArtifacts;
+    private BuildConfiguration buildConfiguration;
+    private Set<String> frameworkNames;
+    private ImmutableSet<Artifact> forceLoadArtifacts;
+    private ImmutableList<String> libraryNames;
+    private NestedSet<String> attributeLinkopts;
+    
+    private final ImmutableSet.Builder<VariableCategory> activeVariableCategoriesBuilder =
+        ImmutableSet.builder();
+
+    /** Sets the {@link RuleContext} for this extension. */
+    public Builder setRuleContext(RuleContext ruleContext) {
+      this.ruleContext = Preconditions.checkNotNull(ruleContext);
+      return this;
+    }
+
+    /** Sets the {@link ObjcProvider} for this extension. */
+    public Builder setObjcProvider(ObjcProvider objcProvider) {
+      this.objcProvider = Preconditions.checkNotNull(objcProvider);
+      return this;
+    }
+
+    /** Sets the {@link CompilationArtifacts} for this extension. */
+    public Builder setCompilationArtifacts(CompilationArtifacts compilationArtifacts) {
+      this.compilationArtifacts = Preconditions.checkNotNull(compilationArtifacts);
+      return this;
+    }
+
+    /** Sets the output of the fully link action. */
+    public Builder setFullyLinkArchive(Artifact fullyLinkArchive) {
+      this.fullyLinkArchive = Preconditions.checkNotNull(fullyLinkArchive);
+      return this;
+    }
+
+    /** Sets the {@link IntermediateArtifacts} for this extension. */
+    public Builder setIntermediateArtifacts(IntermediateArtifacts intermediateArtifacts) {
+      this.intermediateArtifacts = Preconditions.checkNotNull(intermediateArtifacts);
+      return this;
+    }
+
+    /** Sets the configuration for this extension. */
+    public Builder setConfiguration(BuildConfiguration buildConfiguration) {
+      this.buildConfiguration = Preconditions.checkNotNull(buildConfiguration);
+      return this;
+    }
+
+    /** Sets the framework names to be passed to the linker using {@code -framework}. */
+    public Builder setFrameworkNames(Set<String> frameworkNames) {
+      this.frameworkNames = Preconditions.checkNotNull(frameworkNames);
+      return this;
+    }
+    
+    /** Sets binary input files to be passed to the linker with "-l" flags. */
+    public Builder setLibraryNames(ImmutableList<String> libraryNames) {
+      this.libraryNames = Preconditions.checkNotNull(libraryNames);
+      return this;
+    }
+    
+    /** Sets artifacts to be passed to the linker with {@code -force_load}. */
+    public Builder setForceLoadArtifacts(ImmutableSet<Artifact> forceLoadArtifacts) {
+      this.forceLoadArtifacts = Preconditions.checkNotNull(forceLoadArtifacts);
+      return this;
+    }
+    
+    /** Sets linkopts arising from rule attributes. */
+    public Builder setAttributeLinkopts(NestedSet<String> attributeLinkopts) {
+      this.attributeLinkopts = Preconditions.checkNotNull(attributeLinkopts);
+      return this;
+    }
+    
+    /** Sets the given {@link VariableCategory} as active for this extension. */
+    public Builder addVariableCategory(VariableCategory variableCategory) {
+      this.activeVariableCategoriesBuilder.add(Preconditions.checkNotNull(variableCategory));
+      return this;
+    }
+
+    public ObjcVariablesExtension build() {
+      
+      ImmutableSet<VariableCategory> activeVariableCategories =
+          activeVariableCategoriesBuilder.build();
+      
+      Preconditions.checkNotNull(ruleContext, "missing RuleContext");
+      Preconditions.checkNotNull(objcProvider, "missing ObjcProvider");
+      Preconditions.checkNotNull(buildConfiguration, "missing BuildConfiguration");
+      Preconditions.checkNotNull(intermediateArtifacts, "missing IntermediateArtifacts");
+      if (activeVariableCategories.contains(VariableCategory.ARCHIVE_VARIABLES)) {
+        Preconditions.checkNotNull(compilationArtifacts, "missing CompilationArtifacts");
+      }
+      if (activeVariableCategories.contains(VariableCategory.FULLY_LINK_VARIABLES)) {
+        Preconditions.checkNotNull(fullyLinkArchive, "missing fully-link archive");
+      }
+      if (activeVariableCategories.contains(VariableCategory.EXECUTABLE_LINKING_VARIABLES)) {
+        Preconditions.checkNotNull(frameworkNames, "missing framework names");
+        Preconditions.checkNotNull(libraryNames, "missing library names");
+        Preconditions.checkNotNull(forceLoadArtifacts, "missing force-load artifacts");
+        Preconditions.checkNotNull(attributeLinkopts, "missing attribute linkopts");
+      }
+      
+      return new ObjcVariablesExtension(
+          ruleContext,
+          objcProvider,
+          compilationArtifacts,
+          fullyLinkArchive,
+          intermediateArtifacts,
+          buildConfiguration,
+          frameworkNames,
+          libraryNames,
+          forceLoadArtifacts,
+          attributeLinkopts,
+          activeVariableCategories);
+    }
+  }
 }