Add flag -f(no-)modules-implicit-maps.

[djasper]

Summary

This suppresses the implicit search for files called 'module.modulemap' and similar.

[rsmith]

I'm not sure this will do the right thing for framework modules; it looks like we'll infer a module map if you disable implicit module maps for them, which doesn't seem like the right behavior (see HeaderSearch::loadFrameworkModule).

There are a bunch of other functions in this file which do redundant work that we should short-circuit in this case:

• HeaderSearch::lookupModule should bail out after checking to see if we've already loaded the module, rather than looping over the include paths and doing nothing with them.
• HeaderSearch::hasModuleMap should just return immediately, rather than scanning upwards over all parent directories of a file and doing nothing with them.
• HeaderSearch::collectAllModules should skip its loop over all include paths.
• HeaderSearch::loadTopLevelSystemModules should skip its loop over all include paths.
• HeaderSearch::loadSubdirectoryModuleMaps should bail out or assert (it shouldn't be reachable if implicit module maps are disabled).

docs/Modules.rst

211

In the documentation, we should refer to module.modulemap rather than the deprecated name module.map.

include/clang/Basic/LangOptions.def

129

module.modulemap

129

This should be a COMPATIBLE_LANGOPT (or possibly a BENIGN_LANGOPT).

include/clang/Driver/Options.td

678–680

For driver options, we typically include both a -fblah and a -fno-blah (so the user can override earlier command-line options from $CXXFLAGS or similar).

[djasper]

I think HeaderSearch::loadFrameworkModule() should not call ModuleMap::inferFrameworkModule() if implicit maps are deactivated. Inferred maps seems like a special case of implicit maps.

Also addressed all the other points.

docs/Modules.rst

211

Changed.

include/clang/Basic/LangOptions.def

129

Made it a BENIGN_LANGOPT.

129

Done.

include/clang/Driver/Options.td

678–680

Done.

[djasper]

Ping?

[rsmith]

One comment to address, then please go ahead and commit.

lib/Frontend/CompilerInvocation.cpp

1467

You're initializing this from itself if neither flag is set. Did you mean Opts.Modules or Opts.ModuleMaps, or maybe true?

[djasper]

Fixed and submitted as r222745. Thanks!

docs/Modules.rst

``-fmodule-name=module-id``
   Consider a source file as a part of the given module.
 
 ``-fmodule-map-file=<file>``
   Load the given module map file if a header from its directory or one of its subdirectories is loaded.
 
 ``-fmodules-search-all``
   If a symbol is not found, search modules referenced in the current module maps but not imported for symbols, so the error message can reference the module by name.  Note that if the global module index has not been built before, this might take some time as it needs to build all the modules.  Note that this option doesn't apply in module builds, to avoid the recursion.
 
+``-fno-modules-implicit-maps``
+  Suppresses the implicit search for files called ``module.map`` and similar. Instead, module files need to be explicitly specified via ``-fmodule-map-file`` or transitively used.
+
 Module Semantics
 ================
 
 Modules are modeled as if each submodule were a separate translation unit, and a module import makes names from the other translation unit visible. Each submodule starts with a new preprocessor state and an empty translation unit.
 
 .. note::
 
   This behavior is currently only approximated when building a module with submodules. Entities within a submodule that has already been built are visible when building later submodules in that module. This can lead to fragile modules that depend on the build order used for the submodules of the module, and should not be relied upon. This behavior is subject to change.

include/clang/Basic/LangOptions.def

 BENIGN_LANGOPT(EmitAllDecls      , 1, 0, "support for emitting all declarations")
 LANGOPT(MathErrno         , 1, 1, "errno support for math functions")
 BENIGN_LANGOPT(HeinousExtensions , 1, 0, "Extensions that we really don't like and may be ripped out at any time")
 LANGOPT(Modules           , 1, 0, "modules extension to C")
 LANGOPT(ModulesDeclUse    , 1, 0, "require declaration of module uses")
 LANGOPT(ModulesSearchAll  , 1, 1, "search even non-imported modules to find unresolved references")
 LANGOPT(ModulesStrictDeclUse, 1, 0, "require declaration of module uses and all headers to be in modules")
 LANGOPT(ModulesErrorRecovery, 1, 1, "automatically import modules as needed when performing error recovery")
+LANGOPT(ModulesImplicitMaps, 1, 1, "use files called module.map implicitly as module maps")
 COMPATIBLE_LANGOPT(Optimize          , 1, 0, "__OPTIMIZE__ predefined macro")
 COMPATIBLE_LANGOPT(OptimizeSize      , 1, 0, "__OPTIMIZE_SIZE__ predefined macro")
 LANGOPT(Static            , 1, 0, "__STATIC__ predefined macro (as opposed to __DYNAMIC__)")
 VALUE_LANGOPT(PackStruct  , 32, 0,
               "default struct packing maximum alignment")
 VALUE_LANGOPT(MaxTypeAlign  , 32, 0,
               "default maximum alignment for types")
 VALUE_LANGOPT(PICLevel    , 2, 0, "__PIC__ level")

include/clang/Driver/Options.td

 def fmodules_decluse : Flag <["-"], "fmodules-decluse">, Group<f_Group>,
   Flags<[DriverOption,CC1Option]>,
   HelpText<"Require declaration of modules used within a module">;
 def fmodules_strict_decluse : Flag <["-"], "fmodules-strict-decluse">, Group<f_Group>,
   Flags<[DriverOption,CC1Option]>,
   HelpText<"Like -fmodules-decluse but requires all headers to be in modules">;
 def fno_modules_search_all : Flag <["-"], "fno-modules-search-all">, Group<f_Group>,
   Flags<[DriverOption, CC1Option]>;
+def fno_modules_implicit_maps :
+  Flag <["-"], "fno-modules-implicit-maps">,
+  Group<f_Group>, Flags<[DriverOption, CC1Option]>;
 def fretain_comments_from_system_headers : Flag<["-"], "fretain-comments-from-system-headers">, Group<f_Group>, Flags<[CC1Option]>;
 
 def fmudflapth : Flag<["-"], "fmudflapth">, Group<f_Group>;
 def fmudflap : Flag<["-"], "fmudflap">, Group<f_Group>;
 def fnested_functions : Flag<["-"], "fnested-functions">, Group<f_Group>;
 def fnext_runtime : Flag<["-"], "fnext-runtime">, Group<f_Group>;
 def fno_access_control : Flag<["-"], "fno-access-control">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Disable C++ access control">;

include/clang/Lex/HeaderSearch.h

class HeaderSearch {
   /// \brief Entity used to look up stored header file information.
   ExternalHeaderFileInfoSource *ExternalSource;
   
   // Various statistics we track for performance analysis.
   unsigned NumIncluded;
   unsigned NumMultiIncludeFileOptzn;
   unsigned NumFrameworkLookups, NumSubFrameworkLookups;
 
-  bool EnabledModules;
+  const LangOptions &LangOpts;
 
   // HeaderSearch doesn't support default or copy construction.
   HeaderSearch(const HeaderSearch&) LLVM_DELETED_FUNCTION;
   void operator=(const HeaderSearch&) LLVM_DELETED_FUNCTION;
 
   friend class DirectoryLookup;
   
 public:
public:
   /// This routine does not consider the effect of \#import
   bool isFileMultipleIncludeGuarded(const FileEntry *File);
 
   /// CreateHeaderMap - This method returns a HeaderMap for the specified
   /// FileEntry, uniquing them through the 'HeaderMaps' datastructure.
   const HeaderMap *CreateHeaderMap(const FileEntry *FE);
 
   /// Returns true if modules are enabled.
-  bool enabledModules() const { return EnabledModules; }
+  bool enabledModules() const { return LangOpts.Modules; }
 
   /// \brief Retrieve the name of the module file that should be used to 
   /// load the given module.
   ///
   /// \param Module The module whose module file name will be returned.
   ///
   /// \returns The name of the module file that corresponds to this module,
   /// or an empty string if this module does not correspond to any module file.

lib/Frontend/CompilerInvocation.cpp

#include "clang/Frontend/LangStandards.def"
   Opts.Modules = Args.hasArg(OPT_fmodules);
   Opts.ModulesStrictDeclUse = Args.hasArg(OPT_fmodules_strict_decluse);
   Opts.ModulesDeclUse =
       Args.hasArg(OPT_fmodules_decluse) || Opts.ModulesStrictDeclUse;
   Opts.ModulesSearchAll = Opts.Modules &&
     !Args.hasArg(OPT_fno_modules_search_all) &&
     Args.hasArg(OPT_fmodules_search_all);
   Opts.ModulesErrorRecovery = !Args.hasArg(OPT_fno_modules_error_recovery);
+  Opts.ModulesImplicitMaps = !Args.hasArg(OPT_fno_modules_implicit_maps);
   Opts.CharIsSigned = Opts.OpenCL || !Args.hasArg(OPT_fno_signed_char);
   Opts.WChar = Opts.CPlusPlus && !Args.hasArg(OPT_fno_wchar);
   Opts.ShortWChar = Args.hasFlag(OPT_fshort_wchar, OPT_fno_short_wchar, false);
   Opts.ShortEnums = Args.hasArg(OPT_fshort_enums);
   Opts.Freestanding = Args.hasArg(OPT_ffreestanding);
   Opts.NoBuiltin = Args.hasArg(OPT_fno_builtin) || Opts.Freestanding;
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.SizedDeallocation |= Args.hasArg(OPT_fsized_deallocation);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);

lib/Lex/HeaderSearch.cpp

 
 ExternalHeaderFileInfoSource::~ExternalHeaderFileInfoSource() {}
 
 HeaderSearch::HeaderSearch(IntrusiveRefCntPtr<HeaderSearchOptions> HSOpts,
                            SourceManager &SourceMgr, DiagnosticsEngine &Diags,
                            const LangOptions &LangOpts,
                            const TargetInfo *Target)
     : HSOpts(HSOpts), Diags(Diags), FileMgr(SourceMgr.getFileManager()),
-      FrameworkMap(64), ModMap(SourceMgr, Diags, LangOpts, Target, *this) {
+      FrameworkMap(64), ModMap(SourceMgr, Diags, LangOpts, Target, *this),
+      LangOpts(LangOpts) {
   AngledDirIdx = 0;
   SystemDirIdx = 0;
   NoCurDirSearch = false;
 
   ExternalLookup = nullptr;
   ExternalSource = nullptr;
   NumIncluded = 0;
   NumMultiIncludeFileOptzn = 0;
   NumFrameworkLookups = NumSubFrameworkLookups = 0;
-
-  EnabledModules = LangOpts.Modules;
 }
 
 HeaderSearch::~HeaderSearch() {
   // Delete headermaps.
   for (unsigned i = 0, e = HeaderMaps.size(); i != e; ++i)
     delete HeaderMaps[i].second;
 }
 
HeaderSearch::loadModuleMapFileImpl(const FileEntry *File, bool IsSystem) {
   }
 
   // This directory has a module map.
   return LMM_NewlyLoaded;
 }
 
 const FileEntry *
 HeaderSearch::lookupModuleMapFile(const DirectoryEntry *Dir, bool IsFramework) {
+  if (!LangOpts.ModulesImplicitMaps)
+    return nullptr;
   // For frameworks, the preferred spelling is Modules/module.modulemap, but
   // module.map at the framework root is also accepted.
   SmallString<128> ModuleMapFileName(Dir->getName());
   if (IsFramework)
     llvm::sys::path::append(ModuleMapFileName, "Modules");
   llvm::sys::path::append(ModuleMapFileName, "module.modulemap");
   if (const FileEntry *F = FileMgr.getFile(ModuleMapFileName))
     return F;

test/Modules/no-implicit-maps.cpp

+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x objective-c -fno-modules-implicit-maps -fmodules-cache-path=%t -fmodules -I %S/Inputs/private %s -verify
+@import libPrivate1;  // expected-error {{not found}}