[Modules] Add 'no_undeclared_includes' module map attribute

The 'no_undeclared_includes' attribute should be used in a module to
tell that only non-modular headers and headers from used modules are
accepted.

The main motivation behind this is to prevent dep cycles between system
libraries (such as darwin) and libc++.

Patch by Richard Smith!

llvm-svn: 284797

clang/docs/Modules.rst

@@ -365,6 +365,8 @@ The ``system`` attribute specifies that the module is a system module. When a sy
 
 The ``extern_c`` attribute specifies that the module contains C code that can be used from within C++. When such a module is built for use in C++ code, all of the module's headers will be treated as if they were contained within an implicit ``extern "C"`` block. An import for a module with this attribute can appear within an ``extern "C"`` block. No other restrictions are lifted, however: the module currently cannot be imported within an ``extern "C"`` block in a namespace.
 
+The ``no_undeclared_includes`` attribute specifies that the module can only reach non-modular headers and headers from used modules. Since some headers could be present in more than one search path and map to different modules in each path, this mechanism helps clang to find the right header, i.e., prefer the one for the current module or in a submodule instead of the first usual match in the search paths.
+
 Modules can have a number of different kinds of members, each of which is described below:
 
 .. parsed-literal::

clang/include/clang/Basic/Module.h

@@ -201,6 +201,10 @@ class Module {
   /// built.
   unsigned ConfigMacrosExhaustive : 1;
 
+  /// \brief Whether files in this module can only include non-modular headers
+  /// and headers from used modules.
+  unsigned NoUndeclaredIncludes : 1;
+
   /// \brief Describes the visibility of the various names within a
   /// particular module.
   enum NameVisibilityKind {

clang/include/clang/Lex/HeaderSearch.h

@@ -523,8 +523,10 @@ class HeaderSearch {
   /// \brief Retrieve the module that corresponds to the given file, if any.
   ///
   /// \param File The header that we wish to map to a module.
-  ModuleMap::KnownHeader findModuleForHeader(const FileEntry *File) const;
-
+  /// \param AllowTextual Whether we want to find textual headers too.
+  ModuleMap::KnownHeader findModuleForHeader(const FileEntry *File,
+                                             bool AllowTextual = false) const;
+
   /// \brief Read the contents of the given module map file.
   ///
   /// \param File The module map file.

clang/include/clang/Lex/ModuleMap.h

@@ -171,7 +171,8 @@ class ModuleMap {
 
   /// \brief The set of attributes that can be attached to a module.
   struct Attributes {
-    Attributes() : IsSystem(), IsExternC(), IsExhaustive() {}
+    Attributes()
+        : IsSystem(), IsExternC(), IsExhaustive(), NoUndeclaredIncludes() {}
 
     /// \brief Whether this is a system module.
     unsigned IsSystem : 1;
@@ -181,6 +182,10 @@ class ModuleMap {
 
     /// \brief Whether this is an exhaustive set of configuration macros.
     unsigned IsExhaustive : 1;
+
+    /// \brief Whether files in this module can only include non-modular headers
+    /// and headers from used modules.
+    unsigned NoUndeclaredIncludes : 1;
   };
 
   /// \brief A directory for which framework modules can be inferred.
@@ -315,10 +320,15 @@ class ModuleMap {
   ///
   /// \param File The header file that is likely to be included.
   ///
+  /// \param AllowTextual If \c true and \p File is a textual header, return
+  /// its owning module. Otherwise, no KnownHeader will be returned if the
+  /// file is only known as a textual header.
+  ///
   /// \returns The module KnownHeader, which provides the module that owns the
   /// given header file.  The KnownHeader is default constructed to indicate
   /// that no module owns this header file.
-  KnownHeader findModuleForHeader(const FileEntry *File);
+  KnownHeader findModuleForHeader(const FileEntry *File,
+                                  bool AllowTextual = false);
 
   /// \brief Retrieve all the modules that contain the given header file. This
   /// may not include umbrella modules, nor information from external sources,

clang/lib/Basic/Module.cpp

@@ -33,14 +33,16 @@ Module::Module(StringRef Name, SourceLocation DefinitionLoc, Module *Parent,
       IsExplicit(IsExplicit), IsSystem(false), IsExternC(false),
       IsInferred(false), InferSubmodules(false), InferExplicitSubmodules(false),
       InferExportWildcard(false), ConfigMacrosExhaustive(false),
-      NameVisibility(Hidden) {
+      NoUndeclaredIncludes(false), NameVisibility(Hidden) {
   if (Parent) {
     if (!Parent->isAvailable())
       IsAvailable = false;
     if (Parent->IsSystem)
       IsSystem = true;
     if (Parent->IsExternC)
       IsExternC = true;
+    if (Parent->NoUndeclaredIncludes)
+      NoUndeclaredIncludes = true;
     IsMissingRequirement = Parent->IsMissingRequirement;
 
     Parent->SubModuleIndex[Name] = Parent->SubModules.size();
@@ -181,6 +183,11 @@ bool Module::directlyUses(const Module *Requested) const {
   for (auto *Use : Top->DirectUses)
     if (Requested->isSubModuleOf(Use))
       return true;
+
+  // Anyone is allowed to use our builtin stddef.h and its accompanying module.
+  if (!Requested->Parent && Requested->Name == "_Builtin_stddef_max_align_t")
+    return true;
+
   return false;
 }
 

clang/lib/Lex/HeaderSearch.cpp

@@ -413,6 +413,12 @@ getTopFrameworkDir(FileManager &FileMgr, StringRef DirName,
   return TopFrameworkDir;
 }
 
+static bool needModuleLookup(Module *RequestingModule,
+                             bool HasSuggestedModule) {
+  return HasSuggestedModule ||
+         (RequestingModule && RequestingModule->NoUndeclaredIncludes);
+}
+
 /// DoFrameworkLookup - Do a lookup of the specified file in the current
 /// DirectoryLookup, which is a framework directory.
 const FileEntry *DirectoryLookup::DoFrameworkLookup(
@@ -508,7 +514,7 @@ const FileEntry *DirectoryLookup::DoFrameworkLookup(
   }
 
   // If we found the header and are allowed to suggest a module, do so now.
-  if (FE && SuggestedModule) {
+  if (FE && needModuleLookup(RequestingModule, SuggestedModule)) {
     // Find the framework in which this header occurs.
     StringRef FrameworkPath = FE->getDir()->getName();
     bool FoundFramework = false;
@@ -1158,22 +1164,45 @@ bool HeaderSearch::hasModuleMap(StringRef FileName,
 }
 
 ModuleMap::KnownHeader
-HeaderSearch::findModuleForHeader(const FileEntry *File) const {
+HeaderSearch::findModuleForHeader(const FileEntry *File,
+                                  bool AllowTextual) const {
   if (ExternalSource) {
     // Make sure the external source has handled header info about this file,
     // which includes whether the file is part of a module.
     (void)getExistingFileInfo(File);
   }
-  return ModMap.findModuleForHeader(File);
+  return ModMap.findModuleForHeader(File, AllowTextual);
+}
+
+static bool suggestModule(HeaderSearch &HS, const FileEntry *File,
+                          Module *RequestingModule,
+                          ModuleMap::KnownHeader *SuggestedModule) {
+  ModuleMap::KnownHeader Module =
+      HS.findModuleForHeader(File, /*AllowTextual*/true);
+  if (SuggestedModule)
+    *SuggestedModule = (Module.getRole() & ModuleMap::TextualHeader)
+                           ? ModuleMap::KnownHeader()
+                           : Module;
+
+  // If this module specifies [no_undeclared_includes], we cannot find any
+  // file that's in a non-dependency module.
+  if (RequestingModule && Module && RequestingModule->NoUndeclaredIncludes) {
+    HS.getModuleMap().resolveUses(RequestingModule, /*Complain*/false);
+    if (!RequestingModule->directlyUses(Module.getModule())) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 bool HeaderSearch::findUsableModuleForHeader(
     const FileEntry *File, const DirectoryEntry *Root, Module *RequestingModule,
     ModuleMap::KnownHeader *SuggestedModule, bool IsSystemHeaderDir) {
-  if (File && SuggestedModule) {
+  if (File && needModuleLookup(RequestingModule, SuggestedModule)) {
     // If there is a module that corresponds to this header, suggest it.
     hasModuleMap(File->getName(), Root, IsSystemHeaderDir);
-    *SuggestedModule = findModuleForHeader(File);
+    return suggestModule(*this, File, RequestingModule, SuggestedModule);
   }
   return true;
 }
@@ -1182,7 +1211,7 @@ bool HeaderSearch::findUsableModuleForFrameworkHeader(
     const FileEntry *File, StringRef FrameworkName, Module *RequestingModule,
     ModuleMap::KnownHeader *SuggestedModule, bool IsSystemFramework) {
   // If we're supposed to suggest a module, look for one now.
-  if (SuggestedModule) {
+  if (needModuleLookup(RequestingModule, SuggestedModule)) {
     // Find the top-level framework based on this framework.
     SmallVector<std::string, 4> SubmodulePath;
     const DirectoryEntry *TopFrameworkDir
@@ -1199,7 +1228,7 @@ bool HeaderSearch::findUsableModuleForFrameworkHeader(
     // important so that we're consistent about whether this header
     // corresponds to a module. Possibly we should lock down framework modules
     // so that this is not possible.
-    *SuggestedModule = findModuleForHeader(File);
+    return suggestModule(*this, File, RequestingModule, SuggestedModule);
   }
   return true;
 }

clang/lib/Lex/ModuleMap.cpp

@@ -327,9 +327,10 @@ static bool isBetterKnownHeader(const ModuleMap::KnownHeader &New,
   return false;
 }
 
-ModuleMap::KnownHeader ModuleMap::findModuleForHeader(const FileEntry *File) {
+ModuleMap::KnownHeader ModuleMap::findModuleForHeader(const FileEntry *File,
+                                                      bool AllowTextual) {
   auto MakeResult = [&](ModuleMap::KnownHeader R) -> ModuleMap::KnownHeader {
-    if (R.getRole() & ModuleMap::TextualHeader)
+    if (!AllowTextual && R.getRole() & ModuleMap::TextualHeader)
       return ModuleMap::KnownHeader();
     return R;
   };
@@ -674,6 +675,8 @@ Module *ModuleMap::inferFrameworkModule(const DirectoryEntry *FrameworkDir,
           Attrs.IsSystem |= inferred->second.Attrs.IsSystem;
           Attrs.IsExternC |= inferred->second.Attrs.IsExternC;
           Attrs.IsExhaustive |= inferred->second.Attrs.IsExhaustive;
+          Attrs.NoUndeclaredIncludes |=
+              inferred->second.Attrs.NoUndeclaredIncludes;
           ModuleMapFile = inferred->second.ModuleMapFile;
         }
       }
@@ -711,6 +714,7 @@ Module *ModuleMap::inferFrameworkModule(const DirectoryEntry *FrameworkDir,
   Result->IsSystem |= Attrs.IsSystem;
   Result->IsExternC |= Attrs.IsExternC;
   Result->ConfigMacrosExhaustive |= Attrs.IsExhaustive;
+  Result->NoUndeclaredIncludes |= Attrs.NoUndeclaredIncludes;
   Result->Directory = FrameworkDir;
 
   // umbrella header "umbrella-header-name"
@@ -1309,7 +1313,9 @@ namespace {
     /// \brief The 'extern_c' attribute.
     AT_extern_c,
     /// \brief The 'exhaustive' attribute.
-    AT_exhaustive
+    AT_exhaustive,
+    /// \brief The 'no_undeclared_includes' attribute.
+    AT_no_undeclared_includes
   };
 }
 
@@ -1479,6 +1485,9 @@ void ModuleMapParser::parseModuleDecl() {
     ActiveModule->IsSystem = true;
   if (Attrs.IsExternC)
     ActiveModule->IsExternC = true;
+  if (Attrs.NoUndeclaredIncludes ||
+      (!ActiveModule->Parent && ModuleName == "Darwin"))
+    ActiveModule->NoUndeclaredIncludes = true;
   ActiveModule->Directory = Directory;
 
   bool Done = false;
@@ -1845,13 +1854,7 @@ void ModuleMapParser::parseHeaderDecl(MMToken::TokenKind LeadingToken,
         // If Clang supplies this header but the underlying system does not,
         // just silently swap in our builtin version. Otherwise, we'll end
         // up adding both (later).
-        //
-        // For local visibility, entirely replace the system file with our
-        // one and textually include the system one. We need to pass macros
-        // from our header to the system one if we #include_next it.
-        //
-        // FIXME: Can we do this in all cases?
-        if (BuiltinFile && (!File || Map.LangOpts.ModulesLocalVisibility)) {
+        if (BuiltinFile && !File) {
           File = BuiltinFile;
           RelativePathName = BuiltinPathName;
           BuiltinFile = nullptr;
@@ -1877,15 +1880,16 @@ void ModuleMapParser::parseHeaderDecl(MMToken::TokenKind LeadingToken,
       Module::Header H = {RelativePathName.str(), File};
       Map.excludeHeader(ActiveModule, H);
     } else {
-      // If there is a builtin counterpart to this file, add it now, before
-      // the "real" header, so we build the built-in one first when building
-      // the module.
+      // If there is a builtin counterpart to this file, add it now as a textual
+      // header, so it can be #include_next'd by the wrapper header, and can
+      // receive macros from the wrapper header.
       if (BuiltinFile) {
         // FIXME: Taking the name from the FileEntry is unstable and can give
         // different results depending on how we've previously named that file
         // in this build.
         Module::Header H = { BuiltinFile->getName(), BuiltinFile };
-        Map.addHeader(ActiveModule, H, Role);
+        Map.addHeader(ActiveModule, H, ModuleMap::ModuleHeaderRole(
+                                           Role | ModuleMap::TextualHeader));
       }
 
       // Record this header.
@@ -2375,6 +2379,7 @@ bool ModuleMapParser::parseOptionalAttributes(Attributes &Attrs) {
       = llvm::StringSwitch<AttributeKind>(Tok.getString())
           .Case("exhaustive", AT_exhaustive)
           .Case("extern_c", AT_extern_c)
+          .Case("no_undeclared_includes", AT_no_undeclared_includes)
           .Case("system", AT_system)
           .Default(AT_unknown);
     switch (Attribute) {
@@ -2394,6 +2399,10 @@ bool ModuleMapParser::parseOptionalAttributes(Attributes &Attrs) {
     case AT_exhaustive:
       Attrs.IsExhaustive = true;
       break;
+
+    case AT_no_undeclared_includes:
+      Attrs.NoUndeclaredIncludes = true;
+      break;
     }
     consumeToken();
 

clang/test/Modules/Inputs/System/usr/include/stdbool.h

@@ -1 +1 @@
-// Testing hack: does not define bool/true/false.
+#include_next <stdbool.h>

clang/test/Modules/Inputs/libc-libcxx/include/c++/math.h

@@ -0,0 +1,2 @@
+#include_next <math.h>
+template<typename T> T abs(T t) { return (t < 0) ? -t : t; }

clang/test/Modules/Inputs/libc-libcxx/include/c++/module.modulemap

@@ -0,0 +1,4 @@
+module "libc++" {
+  module math { header "math.h" export * }
+  module stdlib { header "stdlib.h" export * }
+}

clang/test/Modules/Inputs/libc-libcxx/include/c++/stdlib.h

@@ -0,0 +1 @@
+#include_next "stdlib.h"

clang/test/Modules/Inputs/libc-libcxx/include/math.h

@@ -0,0 +1 @@
+int abs(int);

clang/test/Modules/Inputs/libc-libcxx/include/module.modulemap

@@ -0,0 +1,4 @@
+module libc [no_undeclared_includes] {
+  module math { header "math.h" export * }
+  module stdlib { header "stdlib.h" export * }
+}

clang/test/Modules/Inputs/libc-libcxx/include/stdlib.h

@@ -0,0 +1 @@
+#include <math.h>

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/__config

@@ -0,0 +1,6 @@
+#ifndef _LIBCPP_CONFIG
+#define _LIBCPP_CONFIG
+
+#define __LIBCXX_CONFIG
+
+#endif

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/math.h

@@ -0,0 +1,7 @@
+#ifndef LIBCXX_MATH_H
+#define LIBCXX_MATH_H
+
+#include_next <math.h>
+template<typename T> T abs(T t) { return (t < 0) ? -t : t; }
+
+#endif

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/module.modulemap

@@ -0,0 +1,7 @@
+module "libc++" {
+  module math { header "math.h" export * }
+  module stdlib { header "stdlib.h" export * }
+  module stddef { header "stddef.h" export * }
+  module stdio { textual header "stdio.h" export * }
+  module __config { header "__config" export * }
+}

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/stddef.h

@@ -0,0 +1,6 @@
+#ifndef LIBCXX_STDDEF_H
+#define LIBCXX_STDDEF_H
+
+#include <__config>
+
+#endif

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/stdio.h

@@ -0,0 +1,6 @@
+#ifndef LIBCXX_STDIO_H
+#define LIBCXX_STDIO_H
+
+#include <__config>
+
+#endif

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/c++/v1/stdlib.h

@@ -0,0 +1,6 @@
+#ifndef LIBCXX_STDLIB_H
+#define LIBCXX_STDLIB_H
+
+#include_next "stdlib.h"
+
+#endif

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/math.h

@@ -0,0 +1 @@
+int abs(int);

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/module.modulemap

@@ -0,0 +1,9 @@
+module libc [no_undeclared_includes] {
+  module math { header "math.h" export * }
+  module stdlib { header "stdlib.h" export * }
+  module stdatomic { header "stdatomic.h" export * }
+  module stddef { header "stddef.h" export * }
+  module stdint { header "stdint.h" export * }
+  module stdio { header "stdio.h" export * }
+  module util { header "util.h" export * }
+}

clang/test/Modules/Inputs/libc-libcxx/sysroot/usr/include/stddef.h

@@ -0,0 +1,2 @@
+// stddef.h
+#include_next "stddef.h"