1 files changed, 34 insertions, 6 deletions

diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index 62f9ba4df32..786d28798ba 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -10,23 +10,51 @@
 #include "Driver.h"
 #include "Error.h"
 #include "Symbols.h"
+#include "llvm/Support/Endian.h"
 #include "llvm/Support/FileOutputBuffer.h"
 #include <memory>
 
 using namespace llvm;
+using namespace llvm::support;
+using namespace llvm::support::endian;
 
 const int PageSize = 4096;
 const uint8_t Magic[32] = "Microsoft C/C++ MSF 7.00\r\n\032DS\0\0";
 
+namespace {
+struct PDBHeader {
+  uint8_t Magic[32];
+  ulittle32_t PageSize;
+  ulittle32_t FpmPage;
+  ulittle32_t PageCount;
+  ulittle32_t RootSize;
+  ulittle32_t Reserved;
+  ulittle32_t RootPointer;
+};
+}
+
 void lld::coff::createPDB(StringRef Path) {
   // Create a file.
   size_t FileSize = PageSize * 3;
-  ErrorOr<std::unique_ptr<FileOutputBuffer>> BufOrErr =
+  ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
       FileOutputBuffer::create(Path, FileSize);
-  error(BufOrErr, Twine("failed to open ") + Path);
-  std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufOrErr);
+  error(BufferOrErr, Twine("failed to open ") + Path);
+  std::unique_ptr<FileOutputBuffer> Buffer = std::move(*BufferOrErr);
+
+  // Write the file header.
+  uint8_t *Buf = Buffer->getBufferStart();
+  auto *Hdr = reinterpret_cast<PDBHeader *>(Buf);
+  memcpy(Hdr->Magic, Magic, sizeof(Magic));
+  Hdr->PageSize = PageSize;
+  // I don't know what FpmPage field means, but it must not be 0.
+  Hdr->FpmPage = 1;
+  Hdr->PageCount = FileSize / PageSize;
+  // Root directory is empty, containing only the length field.
+  Hdr->RootSize = 4;
+  // Root directory is on page 1.
+  Hdr->RootPointer = 1;
 
-  // Write the file magic.
-  uint8_t *P = Buf->getBufferStart();
-  memcpy(P, Magic, sizeof(Magic));
+  // Write the root directory. Root stream is on page 2.
+  write32le(Buf + PageSize, 2);
+  Buffer->commit();
 }