[COFF] create MemoryBuffers without requiring NUL terminators

Summary:
In a number of places in the COFF linker, we were calling
MemoryBuffer::getFile() with default parameters. This causes LLVM to
NUL-terminate the buffers, which can prevent them from being memory
mapped. Since we operate on binary and do not use NUL as an indicator
of the end of the file content, this change causes us to not require
the NUL terminator anymore.

Reviewers: ruiu, pcc

Reviewed By: ruiu

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45909

llvm-svn: 330786

1 files changed, 7 insertions, 3 deletions

diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 73905580044..aa41084d56d 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -105,7 +105,9 @@ static std::future<MBErrPair> createFutureForFile(std::string Path) {
   auto Strategy = std::launch::deferred;
 #endif
   return std::async(Strategy, [=]() {
-    auto MBOrErr = MemoryBuffer::getFile(Path);
+    auto MBOrErr = MemoryBuffer::getFile(Path,
+                                         /*FileSize*/ -1,
+                                         /*RequiresNullTerminator*/ false);
     if (!MBOrErr)
       return MBErrPair{nullptr, MBOrErr.getError()};
     return MBErrPair{std::move(*MBOrErr), std::error_code()};
@@ -563,7 +565,8 @@ static void createImportLibrary(bool AsLib) {
 
   // If the import library already exists, replace it only if the contents
   // have changed.
-  ErrorOr<std::unique_ptr<MemoryBuffer>> OldBuf = MemoryBuffer::getFile(Path);
+  ErrorOr<std::unique_ptr<MemoryBuffer>> OldBuf = MemoryBuffer::getFile(
+      Path, /*FileSize*/ -1, /*RequiresNullTerminator*/ false);
   if (!OldBuf) {
     HandleError(writeImportLibrary(LibName, Path, Exports, Config->Machine,
                                    false, Config->MinGW));
@@ -582,7 +585,8 @@ static void createImportLibrary(bool AsLib) {
     return;
   }
 
-  std::unique_ptr<MemoryBuffer> NewBuf = check(MemoryBuffer::getFile(TmpName));
+  std::unique_ptr<MemoryBuffer> NewBuf = check(MemoryBuffer::getFile(
+      TmpName, /*FileSize*/ -1, /*RequiresNullTerminator*/ false));
   if ((*OldBuf)->getBuffer() != NewBuf->getBuffer()) {
     OldBuf->reset();
     HandleError(errorCodeToError(sys::fs::rename(TmpName, Path)));