lib/WindowsManifest/WindowsManifestMerger.cpp

   1 //===-- WindowsManifestMerger.cpp ------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===---------------------------------------------------------------------===//
   8 //
   9 // This file implements the .manifest merger class.
  10 //
  11 //===---------------------------------------------------------------------===//
  12
  13 #include "llvm/WindowsManifest/WindowsManifestMerger.h"
  14 #include "llvm/Config/config.h"
  15 #include "llvm/Support/MemoryBuffer.h"
  16
  17 #include <map>
  18
  19 #if LLVM_LIBXML2_ENABLED
  20 #include <libxml/xmlreader.h>
  21 #endif
  22
  23 #define TO_XML_CHAR(X) reinterpret_cast<const unsigned char *>(X)
  24 #define FROM_XML_CHAR(X) reinterpret_cast<const char *>(X)
  25
  26 using namespace llvm;
  27 using namespace windows_manifest;
  28
  29 char WindowsManifestError::ID = 0;
  30
  31 WindowsManifestError::WindowsManifestError(const Twine &Msg) : Msg(Msg.str()) {}
  32
  33 void WindowsManifestError::log(raw_ostream &OS) const { OS << Msg; }
  34
  35 class WindowsManifestMerger::WindowsManifestMergerImpl {
  36 public:
  37   ~WindowsManifestMergerImpl();
  38   Error merge(const MemoryBuffer &Manifest);
  39   std::unique_ptr<MemoryBuffer> getMergedManifest();
  40
  41 private:
  42   static void errorCallback(void *Ctx, const char *Format, ...);
  43   Error getParseError();
  44 #if LLVM_LIBXML2_ENABLED
  45   xmlDocPtr CombinedDoc = nullptr;
  46   std::vector<xmlDocPtr> MergedDocs;
  47
  48   bool Merged = false;
  49   struct XmlDeleter {
  50     void operator()(xmlChar *Ptr) { xmlFree(Ptr); }
  51     void operator()(xmlDoc *Ptr) { xmlFreeDoc(Ptr); }
  52   };
  53   int BufferSize = 0;
  54   std::unique_ptr<xmlChar, XmlDeleter> Buffer;
  55 #endif
  56   bool ParseErrorOccurred = false;
  57 };
  58
  59 #if LLVM_LIBXML2_ENABLED
  60
  61 static const std::pair<StringRef, StringRef> MtNsHrefsPrefixes[] = {
  62     {"urn:schemas-microsoft-com:asm.v1", "ms_asmv1"},
  63     {"urn:schemas-microsoft-com:asm.v2", "ms_asmv2"},
  64     {"urn:schemas-microsoft-com:asm.v3", "ms_asmv3"},
  65     {"http://schemas.microsoft.com/SMI/2005/WindowsSettings",
  66      "ms_windowsSettings"},
  67     {"urn:schemas-microsoft-com:compatibility.v1", "ms_compatibilityv1"}};
  68
  69 static bool xmlStringsEqual(const unsigned char *A, const unsigned char *B) {
  70   // Handle null pointers.  Comparison of 2 null pointers returns true because
  71   // this indicates the prefix of a default namespace.
  72   if (!A || !B)
  73     return A == B;
  74   return strcmp(FROM_XML_CHAR(A), FROM_XML_CHAR(B)) == 0;
  75 }
  76
  77 static bool isMergeableElement(const unsigned char *ElementName) {
  78   for (StringRef S : {"application", "assembly", "assemblyIdentity",
  79                       "compatibility", "noInherit", "requestedExecutionLevel",
  80                       "requestedPrivileges", "security", "trustInfo"}) {
  81     if (S == FROM_XML_CHAR(ElementName)) {
  82       return true;
  83     }
  84   }
  85   return false;
  86 }
  87
  88 static xmlNodePtr getChildWithName(xmlNodePtr Parent,
  89                                    const unsigned char *ElementName) {
  90   for (xmlNodePtr Child = Parent->children; Child; Child = Child->next) {
  91     if (xmlStringsEqual(Child->name, ElementName)) {
  92       return Child;
  93     }
  94   }
  95   return nullptr;
  96 }
  97
  98 static xmlAttrPtr getAttribute(xmlNodePtr Node,
  99                                const unsigned char *AttributeName) {
 100   for (xmlAttrPtr Attribute = Node->properties; Attribute != nullptr;
 101        Attribute = Attribute->next) {
 102     if (xmlStringsEqual(Attribute->name, AttributeName)) {
 103       return Attribute;
 104     }
 105   }
 106   return nullptr;
 107 }
 108
 109 // Check if namespace specified by HRef1 overrides that of HRef2.
 110 static bool namespaceOverrides(const unsigned char *HRef1,
 111                                const unsigned char *HRef2) {
 112   auto HRef1Position = llvm::find_if(
 113       MtNsHrefsPrefixes, [=](const std::pair<StringRef, StringRef> &Element) {
 114         return xmlStringsEqual(HRef1, TO_XML_CHAR(Element.first.data()));
 115       });
 116   auto HRef2Position = llvm::find_if(
 117       MtNsHrefsPrefixes, [=](const std::pair<StringRef, StringRef> &Element) {
 118         return xmlStringsEqual(HRef2, TO_XML_CHAR(Element.first.data()));
 119       });
 120   return HRef1Position < HRef2Position;
 121 }
 122
 123 // Search for prefix-defined namespace specified by HRef, starting on Node and
 124 // continuing recursively upwards.  Returns the namespace or nullptr if not
 125 // found.
 126 static xmlNsPtr search(const unsigned char *HRef, xmlNodePtr Node) {
 127   for (xmlNsPtr Def = Node->nsDef; Def; Def = Def->next) {
 128     if (Def->prefix && xmlStringsEqual(Def->href, HRef)) {
 129       return Def;
 130     }
 131   }
 132   if (Node->parent) {
 133     return search(HRef, Node->parent);
 134   }
 135   return nullptr;
 136 }
 137
 138 // Return the prefix that corresponds to the HRef.  If HRef is not a recognized
 139 // URI, then just return the HRef itself to use as the prefix.
 140 static const unsigned char *getPrefixForHref(const unsigned char *HRef) {
 141   for (auto &Ns : MtNsHrefsPrefixes) {
 142     if (xmlStringsEqual(HRef, TO_XML_CHAR(Ns.first.data()))) {
 143       return TO_XML_CHAR(Ns.second.data());
 144     }
 145   }
 146   return HRef;
 147 }
 148
 149 // Search for prefix-defined namespace specified by HRef, starting on Node and
 150 // continuing recursively upwards.  If it is found, then return it.  If it is
 151 // not found, then prefix-define that namespace on the node and return a
 152 // reference to it.
 153 static Expected<xmlNsPtr> searchOrDefine(const unsigned char *HRef,
 154                                          xmlNodePtr Node) {
 155   if (xmlNsPtr Def = search(HRef, Node))
 156     return Def;
 157   if (xmlNsPtr Def = xmlNewNs(Node, HRef, getPrefixForHref(HRef)))
 158     return Def;
 159   return make_error<WindowsManifestError>("failed to create new namespace");
 160 }
 161
 162 // Set the namespace of OrigionalAttribute on OriginalNode to be that of
 163 // AdditionalAttribute's.
 164 static Error copyAttributeNamespace(xmlAttrPtr OriginalAttribute,
 165                                     xmlNodePtr OriginalNode,
 166                                     xmlAttrPtr AdditionalAttribute) {
 167
 168   Expected<xmlNsPtr> ExplicitOrError =
 169       searchOrDefine(AdditionalAttribute->ns->href, OriginalNode);
 170   if (!ExplicitOrError)
 171     return ExplicitOrError.takeError();
 172   OriginalAttribute->ns = std::move(ExplicitOrError.get());
 173   return Error::success();
 174 }
 175
 176 // Return the corresponding namespace definition for the prefix, defined on the
 177 // given Node.  Returns nullptr if there is no such definition.
 178 static xmlNsPtr getNamespaceWithPrefix(const unsigned char *Prefix,
 179                                        xmlNodePtr Node) {
 180   if (Node == nullptr)
 181     return nullptr;
 182   for (xmlNsPtr Def = Node->nsDef; Def; Def = Def->next) {
 183     if (xmlStringsEqual(Def->prefix, Prefix)) {
 184       return Def;
 185     }
 186   }
 187   return nullptr;
 188 }
 189
 190 // Search for the closest inheritable default namespace, starting on (and
 191 // including) the Node and traveling upwards through parent nodes.  Returns
 192 // nullptr if there are no inheritable default namespaces.
 193 static xmlNsPtr getClosestDefault(xmlNodePtr Node) {
 194   if (xmlNsPtr Ret = getNamespaceWithPrefix(nullptr, Node))
 195     return Ret;
 196   if (Node->parent == nullptr)
 197     return nullptr;
 198   return getClosestDefault(Node->parent);
 199 }
 200
 201 // Merge the attributes of AdditionalNode into OriginalNode.  If attributes
 202 // with identical types are present, they are not duplicated but rather if
 203 // their values are not consistent and error is thrown.  In addition, the
 204 // higher priority namespace is used for each attribute, EXCEPT in the case
 205 // of merging two default namespaces and the lower priority namespace
 206 // definition occurs closer than the higher priority one.
 207 static Error mergeAttributes(xmlNodePtr OriginalNode,
 208                              xmlNodePtr AdditionalNode) {
 209   xmlNsPtr ClosestDefault = getClosestDefault(OriginalNode);
 210   for (xmlAttrPtr Attribute = AdditionalNode->properties; Attribute;
 211        Attribute = Attribute->next) {
 212     if (xmlAttrPtr OriginalAttribute =
 213             getAttribute(OriginalNode, Attribute->name)) {
 214       if (!xmlStringsEqual(OriginalAttribute->children->content,
 215                            Attribute->children->content)) {
 216         return make_error<WindowsManifestError>(
 217             Twine("conflicting attributes for ") +
 218             FROM_XML_CHAR(OriginalNode->name));
 219       }
 220       if (!Attribute->ns) {
 221         continue;
 222       }
 223       if (!OriginalAttribute->ns) {
 224         if (auto E = copyAttributeNamespace(OriginalAttribute, OriginalNode,
 225                                             Attribute)) {
 226           return E;
 227         }
 228         continue;
 229       }
 230       if (namespaceOverrides(OriginalAttribute->ns->href,
 231                              Attribute->ns->href)) {
 232         // In this case, the original attribute has a higher priority namespace
 233         // than the incomiing attribute, however the namespace definition of
 234         // the lower priority namespace occurs first traveling upwards in the
 235         // tree.  Therefore the lower priority namespace is applied.
 236         if (!OriginalAttribute->ns->prefix && !Attribute->ns->prefix &&
 237             ClosestDefault &&
 238             xmlStringsEqual(Attribute->ns->href, ClosestDefault->href)) {
 239           if (auto E = copyAttributeNamespace(OriginalAttribute, OriginalNode,
 240                                               Attribute)) {
 241             return E;
 242           }
 243           continue;
 244         }
 245         continue;
 246         // This covers the case where the incoming attribute has the higher
 247         // priority.  The higher priority namespace is applied in all cases
 248         // EXCEPT when both of the namespaces are default inherited, and the
 249         // closest inherited default is the lower priority one.
 250       }
 251       if (Attribute->ns->prefix || OriginalAttribute->ns->prefix ||
 252           (ClosestDefault && !xmlStringsEqual(OriginalAttribute->ns->href,
 253                                               ClosestDefault->href))) {
 254         if (auto E = copyAttributeNamespace(OriginalAttribute, OriginalNode,
 255                                             Attribute)) {
 256           return E;
 257         }
 258         continue;
 259       }
 260       continue;
 261     }
 262     // If the incoming attribute is not already found on the node, append it
 263     // to the end of the properties list.  Also explicitly apply its
 264     // namespace as a prefix because it might be contained in a separate
 265     // namespace that doesn't use the attribute.
 266     xmlAttrPtr NewProp =
 267         xmlNewProp(OriginalNode, Attribute->name, Attribute->children->content);
 268     Expected<xmlNsPtr> ExplicitOrError =
 269         searchOrDefine(Attribute->ns->href, OriginalNode);
 270     if (!ExplicitOrError)
 271       return ExplicitOrError.takeError();
 272     NewProp->ns = std::move(ExplicitOrError.get());
 273   }
 274   return Error::success();
 275 }
 276
 277 // Given two nodes, return the one with the higher priority namespace.
 278 static xmlNodePtr getDominantNode(xmlNodePtr Node1, xmlNodePtr Node2) {
 279
 280   if (!Node1 || !Node1->ns)
 281     return Node2;
 282   if (!Node2 || !Node2->ns)
 283     return Node1;
 284   if (namespaceOverrides(Node1->ns->href, Node2->ns->href))
 285     return Node1;
 286   return Node2;
 287 }
 288
 289 // Checks if this Node's namespace is inherited or one it defined itself.
 290 static bool hasInheritedNs(xmlNodePtr Node) {
 291   return Node->ns && Node->ns != getNamespaceWithPrefix(Node->ns->prefix, Node);
 292 }
 293
 294 // Check if this Node's namespace is a default namespace that it inherited, as
 295 // opposed to defining itself.
 296 static bool hasInheritedDefaultNs(xmlNodePtr Node) {
 297   return hasInheritedNs(Node) && Node->ns->prefix == nullptr;
 298 }
 299
 300 // Check if this Node's namespace is a default namespace it defined itself.
 301 static bool hasDefinedDefaultNamespace(xmlNodePtr Node) {
 302   return Node->ns && (Node->ns == getNamespaceWithPrefix(nullptr, Node));
 303 }
 304
 305 // For the given explicit prefix-definition of a namespace, travel downwards
 306 // from a node recursively, and for every implicit, inherited default usage of
 307 // that namespace replace it with that explicit prefix use.  This is important
 308 // when namespace overriding occurs when merging, so that elements unique to a
 309 // namespace will still stay in that namespace.
 310 static void explicateNamespace(xmlNsPtr PrefixDef, xmlNodePtr Node) {
 311   // If a node as its own default namespace definition it clearly cannot have
 312   // inherited the given default namespace, and neither will any of its
 313   // children.
 314   if (hasDefinedDefaultNamespace(Node))
 315     return;
 316   if (Node->ns && xmlStringsEqual(Node->ns->href, PrefixDef->href) &&
 317       hasInheritedDefaultNs(Node))
 318     Node->ns = PrefixDef;
 319   for (xmlAttrPtr Attribute = Node->properties; Attribute;
 320        Attribute = Attribute->next) {
 321     if (Attribute->ns &&
 322         xmlStringsEqual(Attribute->ns->href, PrefixDef->href)) {
 323       Attribute->ns = PrefixDef;
 324     }
 325   }
 326   for (xmlNodePtr Child = Node->children; Child; Child = Child->next) {
 327     explicateNamespace(PrefixDef, Child);
 328   }
 329 }
 330
 331 // Perform the namespace merge between two nodes.
 332 static Error mergeNamespaces(xmlNodePtr OriginalNode,
 333                              xmlNodePtr AdditionalNode) {
 334   // Save the original default namespace definition in case the incoming node
 335   // overrides it.
 336   const unsigned char *OriginalDefinedDefaultHref = nullptr;
 337   if (xmlNsPtr OriginalDefinedDefaultNs =
 338           getNamespaceWithPrefix(nullptr, OriginalNode)) {
 339     OriginalDefinedDefaultHref = xmlStrdup(OriginalDefinedDefaultNs->href);
 340   }
 341   const unsigned char *NewDefinedDefaultHref = nullptr;
 342   // Copy all namespace definitions.  There can only be one default namespace
 343   // definition per node, so the higher priority one takes precedence in the
 344   // case of collision.
 345   for (xmlNsPtr Def = AdditionalNode->nsDef; Def; Def = Def->next) {
 346     if (xmlNsPtr OriginalNsDef =
 347             getNamespaceWithPrefix(Def->prefix, OriginalNode)) {
 348       if (!Def->prefix) {
 349         if (namespaceOverrides(Def->href, OriginalNsDef->href)) {
 350           NewDefinedDefaultHref = TO_XML_CHAR(strdup(FROM_XML_CHAR(Def->href)));
 351         }
 352       } else if (!xmlStringsEqual(OriginalNsDef->href, Def->href)) {
 353         return make_error<WindowsManifestError>(
 354             Twine("conflicting namespace definitions for ") +
 355             FROM_XML_CHAR(Def->prefix));
 356       }
 357     } else {
 358       xmlNsPtr NewDef = xmlCopyNamespace(Def);
 359       NewDef->next = OriginalNode->nsDef;
 360       OriginalNode->nsDef = NewDef;
 361     }
 362   }
 363
 364   // Check whether the original node or the incoming node has the higher
 365   // priority namespace.  Depending on which one is dominant, we will have
 366   // to recursively apply namespace changes down to children of the original
 367   // node.
 368   xmlNodePtr DominantNode = getDominantNode(OriginalNode, AdditionalNode);
 369   xmlNodePtr NonDominantNode =
 370       DominantNode == OriginalNode ? AdditionalNode : OriginalNode;
 371   if (DominantNode == OriginalNode) {
 372     if (OriginalDefinedDefaultHref) {
 373       xmlNsPtr NonDominantDefinedDefault =
 374           getNamespaceWithPrefix(nullptr, NonDominantNode);
 375       // In this case, both the nodes defined a default namespace.  However
 376       // the lower priority node ended up having a higher priority default
 377       // definition.  This can occur if the higher priority node is prefix
 378       // namespace defined.  In this case we have to define an explicit
 379       // prefix for the overridden definition and apply it to all children
 380       // who relied on that definition.
 381       if (NonDominantDefinedDefault &&
 382           namespaceOverrides(NonDominantDefinedDefault->href,
 383                              OriginalDefinedDefaultHref)) {
 384         Expected<xmlNsPtr> EC =
 385             searchOrDefine(OriginalDefinedDefaultHref, DominantNode);
 386         if (!EC) {
 387           return EC.takeError();
 388         }
 389         xmlNsPtr PrefixDominantDefinedDefault = std::move(EC.get());
 390         explicateNamespace(PrefixDominantDefinedDefault, DominantNode);
 391       }
 392       // In this case the node with a higher priority namespace did not have a
 393       // default namespace definition, but the lower priority node did.  In this
 394       // case the new default namespace definition is copied.  A side effect of
 395       // this is that all children will suddenly find themselves in a different
 396       // default namespace.  To maintain correctness we need to ensure that all
 397       // children now explicitly refer to the namespace that they had previously
 398       // implicitly inherited.
 399     } else if (getNamespaceWithPrefix(nullptr, NonDominantNode)) {
 400       if (DominantNode->parent) {
 401         xmlNsPtr ClosestDefault = getClosestDefault(DominantNode->parent);
 402         Expected<xmlNsPtr> EC =
 403             searchOrDefine(ClosestDefault->href, DominantNode);
 404         if (!EC) {
 405           return EC.takeError();
 406         }
 407         xmlNsPtr ExplicitDefault = std::move(EC.get());
 408         explicateNamespace(ExplicitDefault, DominantNode);
 409       }
 410     }
 411   } else {
 412     // Covers case where the incoming node has a default namespace definition
 413     // that overrides the original node's namespace.  This always leads to
 414     // the original node receiving that new default namespace.
 415     if (hasDefinedDefaultNamespace(DominantNode)) {
 416       NonDominantNode->ns = getNamespaceWithPrefix(nullptr, NonDominantNode);
 417     } else {
 418       // This covers the case where the incoming node either has a prefix
 419       // namespace, or an inherited default namespace.  Since the namespace
 420       // may not yet be defined in the original tree we do a searchOrDefine
 421       // for it, and then set the namespace equal to it.
 422       Expected<xmlNsPtr> EC =
 423           searchOrDefine(DominantNode->ns->href, NonDominantNode);
 424       if (!EC) {
 425         return EC.takeError();
 426       }
 427       xmlNsPtr Explicit = std::move(EC.get());
 428       NonDominantNode->ns = Explicit;
 429     }
 430     // This covers cases where the incoming dominant node HAS a default
 431     // namespace definition, but MIGHT NOT NECESSARILY be in that namespace.
 432     if (xmlNsPtr DominantDefaultDefined =
 433             getNamespaceWithPrefix(nullptr, DominantNode)) {
 434       if (OriginalDefinedDefaultHref) {
 435         if (namespaceOverrides(DominantDefaultDefined->href,
 436                                OriginalDefinedDefaultHref)) {
 437           // In this case, the incoming node's default definition overrides
 438           // the original default definition, all children who relied on that
 439           // definition must be updated accordingly.
 440           Expected<xmlNsPtr> EC =
 441               searchOrDefine(OriginalDefinedDefaultHref, NonDominantNode);
 442           if (!EC) {
 443             return EC.takeError();
 444           }
 445           xmlNsPtr ExplicitDefault = std::move(EC.get());
 446           explicateNamespace(ExplicitDefault, NonDominantNode);
 447         }
 448       } else {
 449         // The original did not define a default definition, however the new
 450         // default definition still applies to all children, so they must be
 451         // updated to explicitly refer to the namespace they had previously
 452         // been inheriting implicitly.
 453         xmlNsPtr ClosestDefault = getClosestDefault(NonDominantNode);
 454         Expected<xmlNsPtr> EC =
 455             searchOrDefine(ClosestDefault->href, NonDominantNode);
 456         if (!EC) {
 457           return EC.takeError();
 458         }
 459         xmlNsPtr ExplicitDefault = std::move(EC.get());
 460         explicateNamespace(ExplicitDefault, NonDominantNode);
 461       }
 462     }
 463   }
 464   if (NewDefinedDefaultHref) {
 465     xmlNsPtr OriginalNsDef = getNamespaceWithPrefix(nullptr, OriginalNode);
 466     xmlFree(const_cast<unsigned char *>(OriginalNsDef->href));
 467     OriginalNsDef->href = NewDefinedDefaultHref;
 468   }
 469   xmlFree(const_cast<unsigned char *>(OriginalDefinedDefaultHref));
 470   return Error::success();
 471 }
 472
 473 static bool isRecognizedNamespace(const unsigned char *NsHref) {
 474   for (auto &Ns : MtNsHrefsPrefixes) {
 475     if (xmlStringsEqual(NsHref, TO_XML_CHAR(Ns.first.data()))) {
 476       return true;
 477     }
 478   }
 479   return false;
 480 }
 481
 482 static bool hasRecognizedNamespace(xmlNodePtr Node) {
 483   return isRecognizedNamespace(Node->ns->href);
 484 }
 485
 486 // Ensure a node's inherited namespace is actually defined in the tree it
 487 // resides in.
 488 static Error reconcileNamespaces(xmlNodePtr Node) {
 489   if (!Node) {
 490     return Error::success();
 491   }
 492   if (hasInheritedNs(Node)) {
 493     Expected<xmlNsPtr> ExplicitOrError = searchOrDefine(Node->ns->href, Node);
 494     if (!ExplicitOrError) {
 495       return ExplicitOrError.takeError();
 496     }
 497     xmlNsPtr Explicit = std::move(ExplicitOrError.get());
 498     Node->ns = Explicit;
 499   }
 500   for (xmlNodePtr Child = Node->children; Child; Child = Child->next) {
 501     if (auto E = reconcileNamespaces(Child)) {
 502       return E;
 503     }
 504   }
 505   return Error::success();
 506 }
 507
 508 // Recursively merge the two given manifest trees, depending on which elements
 509 // are of a mergeable type, and choose namespaces according to which have
 510 // higher priority.
 511 static Error treeMerge(xmlNodePtr OriginalRoot, xmlNodePtr AdditionalRoot) {
 512   if (auto E = mergeAttributes(OriginalRoot, AdditionalRoot))
 513     return E;
 514   if (auto E = mergeNamespaces(OriginalRoot, AdditionalRoot))
 515     return E;
 516   xmlNodePtr AdditionalFirstChild = AdditionalRoot->children;
 517   xmlNode StoreNext;
 518   for (xmlNodePtr Child = AdditionalFirstChild; Child; Child = Child->next) {
 519     xmlNodePtr OriginalChildWithName;
 520     if (!isMergeableElement(Child->name) ||
 521         !(OriginalChildWithName =
 522               getChildWithName(OriginalRoot, Child->name)) ||
 523         !hasRecognizedNamespace(Child)) {
 524       StoreNext.next = Child->next;
 525       xmlUnlinkNode(Child);
 526       if (!xmlAddChild(OriginalRoot, Child)) {
 527         return make_error<WindowsManifestError>(Twine("could not merge ") +
 528                                                 FROM_XML_CHAR(Child->name));
 529       }
 530       if (auto E = reconcileNamespaces(Child)) {
 531         return E;
 532       }
 533       Child = &StoreNext;
 534     } else if (auto E = treeMerge(OriginalChildWithName, Child)) {
 535       return E;
 536     }
 537   }
 538   return Error::success();
 539 }
 540
 541 static void stripComments(xmlNodePtr Root) {
 542   xmlNode StoreNext;
 543   for (xmlNodePtr Child = Root->children; Child; Child = Child->next) {
 544     if (!xmlStringsEqual(Child->name, TO_XML_CHAR("comment"))) {
 545       stripComments(Child);
 546       continue;
 547     }
 548     StoreNext.next = Child->next;
 549     xmlNodePtr Remove = Child;
 550     Child = &StoreNext;
 551     xmlUnlinkNode(Remove);
 552     xmlFreeNode(Remove);
 553   }
 554 }
 555
 556 // libxml2 assumes that attributes do not inherit default namespaces, whereas
 557 // the original  mt.exe does make this assumption.  This function reconciles
 558 // this by setting all attributes to have the inherited default namespace.
 559 static void setAttributeNamespaces(xmlNodePtr Node) {
 560   for (xmlAttrPtr Attribute = Node->properties; Attribute;
 561        Attribute = Attribute->next) {
 562     if (!Attribute->ns) {
 563       Attribute->ns = getClosestDefault(Node);
 564     }
 565   }
 566   for (xmlNodePtr Child = Node->children; Child; Child = Child->next) {
 567     setAttributeNamespaces(Child);
 568   }
 569 }
 570
 571 // The merging process may create too many prefix defined namespaces.  This
 572 // function removes all unnecessary ones from the tree.
 573 static void checkAndStripPrefixes(xmlNodePtr Node,
 574                                   std::vector<xmlNsPtr> &RequiredPrefixes) {
 575   for (xmlNodePtr Child = Node->children; Child; Child = Child->next) {
 576     checkAndStripPrefixes(Child, RequiredPrefixes);
 577   }
 578   if (Node->ns && Node->ns->prefix != nullptr) {
 579     xmlNsPtr ClosestDefault = getClosestDefault(Node);
 580     if (ClosestDefault &&
 581         xmlStringsEqual(ClosestDefault->href, Node->ns->href)) {
 582       Node->ns = ClosestDefault;
 583     } else if (!llvm::is_contained(RequiredPrefixes, Node->ns)) {
 584       RequiredPrefixes.push_back(Node->ns);
 585     }
 586   }
 587   for (xmlAttrPtr Attribute = Node->properties; Attribute;
 588        Attribute = Attribute->next) {
 589     if (Attribute->ns && Attribute->ns->prefix != nullptr) {
 590       xmlNsPtr ClosestDefault = getClosestDefault(Node);
 591       if (ClosestDefault &&
 592           xmlStringsEqual(ClosestDefault->href, Attribute->ns->href)) {
 593         Attribute->ns = ClosestDefault;
 594       } else if (!llvm::is_contained(RequiredPrefixes, Node->ns)) {
 595         RequiredPrefixes.push_back(Attribute->ns);
 596       }
 597     }
 598   }
 599   xmlNsPtr Prev;
 600   xmlNs Temp;
 601   for (xmlNsPtr Def = Node->nsDef; Def; Def = Def->next) {
 602     if (!Def->prefix || llvm::is_contained(RequiredPrefixes, Def)) {
 603       Prev = Def;
 604       continue;
 605     }
 606     if (Def == Node->nsDef) {
 607       Node->nsDef = Def->next;
 608     } else {
 609       Prev->next = Def->next;
 610     }
 611     Temp.next = Def->next;
 612     xmlFreeNs(Def);
 613     Def = &Temp;
 614   }
 615 }
 616
 617 WindowsManifestMerger::WindowsManifestMergerImpl::~WindowsManifestMergerImpl() {
 618   for (auto &Doc : MergedDocs)
 619     xmlFreeDoc(Doc);
 620 }
 621
 622 Error WindowsManifestMerger::WindowsManifestMergerImpl::merge(
 623     const MemoryBuffer &Manifest) {
 624   if (Merged)
 625     return make_error<WindowsManifestError>(
 626         "merge after getMergedManifest is not supported");
 627   if (Manifest.getBufferSize() == 0)
 628     return make_error<WindowsManifestError>(
 629         "attempted to merge empty manifest");
 630   xmlSetGenericErrorFunc((void *)this,
 631                          WindowsManifestMergerImpl::errorCallback);
 632   xmlDocPtr ManifestXML = xmlReadMemory(
 633       Manifest.getBufferStart(), Manifest.getBufferSize(), "manifest.xml",
 634       nullptr, XML_PARSE_NOBLANKS | XML_PARSE_NODICT);
 635   xmlSetGenericErrorFunc(nullptr, nullptr);
 636   if (auto E = getParseError())
 637     return E;
 638   xmlNodePtr AdditionalRoot = xmlDocGetRootElement(ManifestXML);
 639   stripComments(AdditionalRoot);
 640   setAttributeNamespaces(AdditionalRoot);
 641   if (CombinedDoc == nullptr) {
 642     CombinedDoc = ManifestXML;
 643   } else {
 644     xmlNodePtr CombinedRoot = xmlDocGetRootElement(CombinedDoc);
 645     if (!xmlStringsEqual(CombinedRoot->name, AdditionalRoot->name) ||
 646         !isMergeableElement(AdditionalRoot->name) ||
 647         !hasRecognizedNamespace(AdditionalRoot)) {
 648       return make_error<WindowsManifestError>("multiple root nodes");
 649     }
 650     if (auto E = treeMerge(CombinedRoot, AdditionalRoot)) {
 651       return E;
 652     }
 653   }
 654   MergedDocs.push_back(ManifestXML);
 655   return Error::success();
 656 }
 657
 658 std::unique_ptr<MemoryBuffer>
 659 WindowsManifestMerger::WindowsManifestMergerImpl::getMergedManifest() {
 660   if (!Merged) {
 661     Merged = true;
 662
 663     if (!CombinedDoc)
 664       return nullptr;
 665
 666     xmlNodePtr CombinedRoot = xmlDocGetRootElement(CombinedDoc);
 667     std::vector<xmlNsPtr> RequiredPrefixes;
 668     checkAndStripPrefixes(CombinedRoot, RequiredPrefixes);
 669     std::unique_ptr<xmlDoc, XmlDeleter> OutputDoc(
 670         xmlNewDoc((const unsigned char *)"1.0"));
 671     xmlDocSetRootElement(OutputDoc.get(), CombinedRoot);
 672     assert(0 == xmlDocGetRootElement(CombinedDoc));
 673
 674     xmlKeepBlanksDefault(0);
 675     xmlChar *Buff = nullptr;
 676     xmlDocDumpFormatMemoryEnc(OutputDoc.get(), &Buff, &BufferSize, "UTF-8", 1);
 677     Buffer.reset(Buff);
 678   }
 679
 680   return BufferSize ? MemoryBuffer::getMemBufferCopy(StringRef(
 681                           FROM_XML_CHAR(Buffer.get()), (size_t)BufferSize))
 682                     : nullptr;
 683 }
 684
 685 bool windows_manifest::isAvailable() { return true; }
 686
 687 #else
 688
 689 WindowsManifestMerger::WindowsManifestMergerImpl::~WindowsManifestMergerImpl() {
 690 }
 691
 692 Error WindowsManifestMerger::WindowsManifestMergerImpl::merge(
 693     const MemoryBuffer &Manifest) {
 694   return make_error<WindowsManifestError>("no libxml2");
 695 }
 696
 697 std::unique_ptr<MemoryBuffer>
 698 WindowsManifestMerger::WindowsManifestMergerImpl::getMergedManifest() {
 699   return nullptr;
 700 }
 701
 702 bool windows_manifest::isAvailable() { return false; }
 703
 704 #endif
 705
 706 WindowsManifestMerger::WindowsManifestMerger()
 707     : Impl(make_unique<WindowsManifestMergerImpl>()) {}
 708
 709 WindowsManifestMerger::~WindowsManifestMerger() {}
 710
 711 Error WindowsManifestMerger::merge(const MemoryBuffer &Manifest) {
 712   return Impl->merge(Manifest);
 713 }
 714
 715 std::unique_ptr<MemoryBuffer> WindowsManifestMerger::getMergedManifest() {
 716   return Impl->getMergedManifest();
 717 }
 718
 719 void WindowsManifestMerger::WindowsManifestMergerImpl::errorCallback(
 720     void *Ctx, const char *Format, ...) {
 721   auto *Merger = (WindowsManifestMergerImpl *)Ctx;
 722   Merger->ParseErrorOccurred = true;
 723 }
 724
 725 Error WindowsManifestMerger::WindowsManifestMergerImpl::getParseError() {
 726   if (!ParseErrorOccurred)
 727     return Error::success();
 728   return make_error<WindowsManifestError>("invalid xml document");
 729 }