[Support/MemoryBuffer] Move the IsVolatile check inside shouldUseMmap() and make sure to zero-initialize the rest
of the buffer if we unexpectedly reach end-of-file while reading.
llvm-svn: 208021
diff --git a/llvm/lib/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index dc615d2..a42138c 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -305,7 +305,14 @@
size_t MapSize,
off_t Offset,
bool RequiresNullTerminator,
- int PageSize) {
+ int PageSize,
+ bool IsVolatile) {
+ // mmap may leave the buffer without null terminator if the file size changed
+ // by the time the last page is mapped in, so avoid it if the file size is
+ // likely to change.
+ if (IsVolatile)
+ return false;
+
// We don't use mmap for small files because this can severely fragment our
// address space.
if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
@@ -381,9 +388,8 @@
MapSize = FileSize;
}
- if (!IsVolatile &&
- shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
- PageSize)) {
+ if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
+ PageSize, IsVolatile)) {
error_code EC;
Result.reset(new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile(
RequiresNullTerminator, FD, MapSize, Offset, EC));
@@ -420,9 +426,9 @@
return error_code(errno, posix_category());
}
if (NumRead == 0) {
- assert(0 && "We got inaccurate FileSize value or fstat reported an "
- "invalid file size.");
- *BufPtr = '\0'; // null-terminate at the actual size.
+ assert(IsVolatile && "We got inaccurate FileSize value or fstat reported "
+ "an invalid file size.");
+ memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
break;
}
BytesLeft -= NumRead;