File::Read(), when asked to read the contents of a file into a heap

buffer and to add a nul terminator byte, was incorrectly resizing
its buffer so the nul terminator was not included.

Problem found by clang ASAN instrumentation when using an
expression prefix file which was read via this mechanism.

<rdar://problem/19556459> 

llvm-svn: 226753

1 files changed, 4 insertions, 3 deletions

diff --git a/lldb/source/Host/common/File.cpp b/lldb/source/Host/common/File.cpp
index c3c77835ce8..8568d8f1041 100644
--- a/lldb/source/Host/common/File.cpp
+++ b/lldb/source/Host/common/File.cpp
@@ -742,8 +742,9 @@ File::Read (size_t &num_bytes, off_t &offset, bool null_terminate, DataBufferSP
                     if (num_bytes > bytes_left)
                         num_bytes = bytes_left;
                         
+                    size_t num_bytes_plus_nul_char = num_bytes + (null_terminate ? 1 : 0);
                     std::unique_ptr<DataBufferHeap> data_heap_ap;
-                    data_heap_ap.reset(new DataBufferHeap(num_bytes + (null_terminate ? 1 : 0), '\0'));
+                    data_heap_ap.reset(new DataBufferHeap(num_bytes_plus_nul_char, '\0'));
                         
                     if (data_heap_ap.get())
                     {
@@ -752,8 +753,8 @@ File::Read (size_t &num_bytes, off_t &offset, bool null_terminate, DataBufferSP
                         {
                             // Make sure we read exactly what we asked for and if we got
                             // less, adjust the array
-                            if (num_bytes < data_heap_ap->GetByteSize())
-                                data_heap_ap->SetByteSize(num_bytes);
+                            if (num_bytes_plus_nul_char < data_heap_ap->GetByteSize())
+                                data_heap_ap->SetByteSize(num_bytes_plus_nul_char);
                             data_buffer_sp.reset(data_heap_ap.release());
                             return error;
                         }