Basic: Add native support for stdin to SourceManager and FileManager

Add support for stdin to SourceManager and FileManager. Adds
FileManager::getSTDIN, which adds a FileEntryRef for `<stdin>` and reads
the MemoryBuffer, which is stored as `FileEntry::Content`.

Eventually the other buffers in `ContentCache` will sink to here as well
-- we probably usually want to load/save a MemoryBuffer eagerly -- but
it's happening early for stdin to get rid of
CompilerInstance::InitializeSourceManager's final call to
`SourceManager::overrideFileContents`.

clang/test/CXX/modules-ts/dcl.dcl/dcl.module/dcl.module.export/p1.cpp
relies on building a module from stdin; supporting that requires setting
ContentCache::BufferOverridden.

Differential Revision: https://reviews.llvm.org/D93148

1 files changed, 12 insertions, 23 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index d96afae..5c413ec 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -848,33 +848,22 @@ bool CompilerInstance::InitializeSourceManager(const FrontendInputFile &Input,
   StringRef InputFile = Input.getFile();
 
   // Figure out where to get and map in the main file.
-  if (InputFile != "-") {
-    auto FileOrErr = FileMgr.getFileRef(InputFile, /*OpenFile=*/true);
-    if (!FileOrErr) {
-      // FIXME: include the error in the diagnostic.
-      consumeError(FileOrErr.takeError());
+  auto FileOrErr = InputFile == "-"
+                       ? FileMgr.getSTDIN()
+                       : FileMgr.getFileRef(InputFile, /*OpenFile=*/true);
+  if (!FileOrErr) {
+    // FIXME: include the error in the diagnostic even when it's not stdin.
+    auto EC = llvm::errorToErrorCode(FileOrErr.takeError());
+    if (InputFile != "-")
       Diags.Report(diag::err_fe_error_reading) << InputFile;
-      return false;
-    }
-
-    SourceMgr.setMainFileID(
-        SourceMgr.createFileID(*FileOrErr, SourceLocation(), Kind));
-  } else {
-    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> SBOrErr =
-        llvm::MemoryBuffer::getSTDIN();
-    if (std::error_code EC = SBOrErr.getError()) {
+    else
       Diags.Report(diag::err_fe_error_reading_stdin) << EC.message();
-      return false;
-    }
-    std::unique_ptr<llvm::MemoryBuffer> SB = std::move(SBOrErr.get());
-
-    FileEntryRef File = FileMgr.getVirtualFileRef(SB->getBufferIdentifier(),
-                                                  SB->getBufferSize(), 0);
-    SourceMgr.setMainFileID(
-        SourceMgr.createFileID(File, SourceLocation(), Kind));
-    SourceMgr.overrideFileContents(File, std::move(SB));
+    return false;
   }
 
+  SourceMgr.setMainFileID(
+      SourceMgr.createFileID(*FileOrErr, SourceLocation(), Kind));
+
   assert(SourceMgr.getMainFileID().isValid() &&
          "Couldn't establish MainFileID!");
   return true;