Detect when we end up trying to load conflicting module files.

This can happen when one abuses precompiled headers by passing more -D
options when using a precompiled hedaer than when it was built. This
is intentionally permitted by precompiled headers (and is exploited by
some build environments), but causes problems for modules.

First part of <rdar://problem/13165109>, detecting when something when
horribly wrong.

llvm-svn: 174554

1 files changed, 18 insertions, 3 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index d4a351394a2..b6115ec6ffa 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -915,9 +915,9 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
     // Search for a module with the given name.
     Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
     std::string ModuleFileName;
-    if (Module)
+    if (Module) {
       ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(Module);
-    else
+    } else
       ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(ModuleName);
 
     if (ModuleFileName.empty()) {
@@ -987,6 +987,20 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
       return ModuleLoadResult();
     }
 
+    // If there is already a module file associated with this module, make sure
+    // it is the same as the module file we're looking for. Otherwise, we
+    // have two module files for the same module.
+    if (const FileEntry *CurModuleFile = Module? Module->getASTFile() : 0) {
+      if (CurModuleFile != ModuleFile) {
+        getDiagnostics().Report(ModuleNameLoc, diag::err_module_file_conflict)
+          << ModuleName
+          << CurModuleFile->getName()
+          << ModuleFile->getName();
+        ModuleBuildFailed = true;
+        return ModuleLoadResult();
+      }
+    }
+
     // If we don't already have an ASTReader, create one now.
     if (!ModuleManager) {
       if (!hasASTContext())
@@ -1085,8 +1099,9 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
                  .findModule((Path[0].first->getName()));
     }
 
-    if (Module)
+    if (Module) {
       Module->setASTFile(ModuleFile);
+    }
     
     // Cache the result of this top-level module lookup for later.
     Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;