Fix crash when multiple raw_fd_ostreams to stdout are created.

If raw_fd_ostream is constructed with the path of "-", it claims
ownership of the stdout file descriptor. This means that it closes
stdout when it is destroyed. If there are multiple users of
raw_fd_ostream wrapped around stdout, then a crash can occur because
of operations on a closed stream.

An example of this would be running something like "clang -S -o - -MD
-MF - test.cpp". Alternatively, using outs() (which creates a local
version of raw_fd_stream to stdout) anywhere combined with such a
stream usage would cause the crash.

The fix duplicates the stdout file descriptor when used within
raw_fd_ostream, so that only that particular descriptor is closed when
the stream is destroyed.

Patch by James Henderson!

llvm-svn: 297624

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index d073802db93..5deab5de4f6 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -473,7 +473,7 @@ static int getFD(StringRef Filename, std::error_code &EC,
     // possible.
     if (!(Flags & sys::fs::F_Text))
       sys::ChangeStdoutToBinary();
-    return STDOUT_FILENO;
+    return dup(STDOUT_FILENO);
   }
 
   int FD;