[PATCH] D45909: [COFF] create MemoryBuffers without requiring NUL terminators

[Bob Haarman via Phabricator via llvm-commits]

inglorion created this revision.
inglorion added reviewers: ruiu, pcc.

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.


https://reviews.llvm.org/D45909

Files:
  lld/COFF/Driver.cpp


Index: lld/COFF/Driver.cpp
===================================================================
--- lld/COFF/Driver.cpp
+++ lld/COFF/Driver.cpp
@@ -105,7 +105,9 @@
   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 @@
 
   // 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 @@
     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)));


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