<rdar://problem/10796651> Introduce configuration macros into module maps.

Configuration macros are macros that are intended to alter how a
module works, such that we need to build different module variants
for different values of these macros. A module can declare its
configuration macros, in which case we will complain if the definition
of a configation macro on the command line (or lack thereof) differs
from the current preprocessor state at the point where the module is
imported. This should eliminate some surprises when enabling modules,
because "#define CONFIG_MACRO ..." followed by "#include
<module/header.h>" would silently ignore the CONFIG_MACRO setting. At
least it will no longer be silent about it.

Configuration macros are eventually intended to help reduce the number
of module variants that need to be built. When the list of
configuration macros for a module is exhaustive, we only need to
consider the settings for those macros when building/finding the
module, which can help isolate modules for various project-specific -D
flags that should never affect how modules are build (but currently do).

llvm-svn: 177466

clang/lib/Lex/ModuleMap.cpp

@@ -643,6 +643,7 @@ namespace clang {
   struct MMToken {
     enum TokenKind {
       Comma,
+      ConfigMacros,
       EndOfFile,
       HeaderKeyword,
       Identifier,
@@ -687,10 +688,13 @@ namespace clang {
 
   /// \brief The set of attributes that can be attached to a module.
   struct Attributes {
-    Attributes() : IsSystem() { }
+    Attributes() : IsSystem(), IsExhaustive() { }
 
     /// \brief Whether this is a system module.
     unsigned IsSystem : 1;
+
+    /// \brief Whether this is an exhaustive set of configuration macros.
+    unsigned IsExhaustive : 1;
   };
   
 
@@ -739,6 +743,7 @@ namespace clang {
     void parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
     void parseExportDecl();
     void parseLinkDecl();
+    void parseConfigMacros();
     void parseInferredModuleDecl(bool Framework, bool Explicit);
     bool parseOptionalAttributes(Attributes &Attrs);
 
@@ -776,11 +781,12 @@ retry:
     Tok.StringData = LToken.getRawIdentifierData();
     Tok.StringLength = LToken.getLength();
     Tok.Kind = llvm::StringSwitch<MMToken::TokenKind>(Tok.getString())
-                 .Case("header", MMToken::HeaderKeyword)
+                 .Case("config_macros", MMToken::ConfigMacros)
                  .Case("exclude", MMToken::ExcludeKeyword)
                  .Case("explicit", MMToken::ExplicitKeyword)
                  .Case("export", MMToken::ExportKeyword)
                  .Case("framework", MMToken::FrameworkKeyword)
+                 .Case("header", MMToken::HeaderKeyword)
                  .Case("link", MMToken::LinkKeyword)
                  .Case("module", MMToken::ModuleKeyword)
                  .Case("requires", MMToken::RequiresKeyword)
@@ -937,7 +943,9 @@ namespace {
     /// \brief An unknown attribute.
     AT_unknown,
     /// \brief The 'system' attribute.
-    AT_system
+    AT_system,
+    /// \brief The 'exhaustive' attribute.
+    AT_exhaustive
   };
 }
 
@@ -1094,7 +1102,11 @@ void ModuleMapParser::parseModuleDecl() {
     case MMToken::RBrace:
       Done = true;
       break;
-        
+
+    case MMToken::ConfigMacros:
+      parseConfigMacros();
+      break;
+
     case MMToken::ExplicitKeyword:
     case MMToken::FrameworkKeyword:
     case MMToken::ModuleKeyword:
@@ -1489,6 +1501,59 @@ void ModuleMapParser::parseLinkDecl() {
                                                             IsFramework));
 }
 
+/// \brief Parse a configuration macro declaration.
+///
+///   module-declaration:
+///     'config_macros' attributes[opt] config-macro-list?
+///
+///   config-macro-list:
+///     identifier (',' identifier)?
+void ModuleMapParser::parseConfigMacros() {
+  assert(Tok.is(MMToken::ConfigMacros));
+  SourceLocation ConfigMacrosLoc = consumeToken();
+
+  // Only top-level modules can have configuration macros.
+  if (ActiveModule->Parent) {
+    Diags.Report(ConfigMacrosLoc, diag::err_mmap_config_macro_submodule);
+  }
+
+  // Parse the optional attributes.
+  Attributes Attrs;
+  parseOptionalAttributes(Attrs);
+  if (Attrs.IsExhaustive && !ActiveModule->Parent) {
+    ActiveModule->ConfigMacrosExhaustive = true;
+  }
+
+  // If we don't have an identifier, we're done.
+  if (!Tok.is(MMToken::Identifier))
+    return;
+
+  // Consume the first identifier.
+  if (!ActiveModule->Parent) {
+    ActiveModule->ConfigMacros.push_back(Tok.getString().str());
+  }
+  consumeToken();
+
+  do {
+    // If there's a comma, consume it.
+    if (!Tok.is(MMToken::Comma))
+      break;
+    consumeToken();
+
+    // We expect to see a macro name here.
+    if (!Tok.is(MMToken::Identifier)) {
+      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_config_macro);
+      break;
+    }
+
+    // Consume the macro name.
+    if (!ActiveModule->Parent) {
+      ActiveModule->ConfigMacros.push_back(Tok.getString().str());
+    }
+    consumeToken();
+  } while (true);
+}
+
 /// \brief Parse an inferred module declaration (wildcard modules).
 ///
 ///   module-declaration:
@@ -1668,6 +1733,7 @@ bool ModuleMapParser::parseOptionalAttributes(Attributes &Attrs) {
     // Decode the attribute name.
     AttributeKind Attribute
       = llvm::StringSwitch<AttributeKind>(Tok.getString())
+          .Case("exhaustive", AT_exhaustive)
           .Case("system", AT_system)
           .Default(AT_unknown);
     switch (Attribute) {
@@ -1679,6 +1745,10 @@ bool ModuleMapParser::parseOptionalAttributes(Attributes &Attrs) {
     case AT_system:
       Attrs.IsSystem = true;
       break;
+
+    case AT_exhaustive:
+      Attrs.IsExhaustive = true;
+      break;
     }
     consumeToken();
 
@@ -1730,6 +1800,7 @@ bool ModuleMapParser::parseModuleMapFile() {
       break;
 
     case MMToken::Comma:
+    case MMToken::ConfigMacros:
     case MMToken::ExcludeKeyword:
     case MMToken::ExportKeyword:
     case MMToken::HeaderKeyword: