From e53477e56ce6ead4a17e66c53689c8feb2df7dd5 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 28 May 2004 00:34:42 +0000
Subject: [PATCH] Add support for zero length files

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13866 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Support/FileUtilities.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/Support/FileUtilities.cpp b/lib/Support/FileUtilities.cpp
index 74df8b253c2..ed594db96ea 100644
--- a/lib/Support/FileUtilities.cpp
+++ b/lib/Support/FileUtilities.cpp
@@ -230,11 +230,17 @@ void *llvm::ReadFileIntoAddressSpace(const std::string &Filename,
   FDHandle FD(open(Filename.c_str(), O_RDONLY));
   if (FD == -1) return 0;
 
+  // If the file has a length of zero, mmap might return a null pointer.  In 
+  // this case, allocate a single byte of memory and return it instead.
+  if (Length == 0)
+    return malloc(1);
+
   // mmap in the file all at once...
   void *Buffer = (void*)mmap(0, Length, PROT_READ, MAP_PRIVATE, FD, 0);
 
   if (Buffer == (void*)MAP_FAILED)
     return 0;
+
   return Buffer;
 #else
   // FIXME: implement with read/write
@@ -246,7 +252,10 @@ void *llvm::ReadFileIntoAddressSpace(const std::string &Filename,
 /// address space.
 void llvm::UnmapFileFromAddressSpace(void *Buffer, unsigned Length) {
 #ifdef HAVE_MMAP_FILE
-  munmap((char*)Buffer, Length);
+  if (Length)
+    munmap((char*)Buffer, Length);
+  else
+    free(Buffer);  // Zero byte files are malloc(1)'s.
 #else
   free(Buffer);
 #endif