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, 8 insertions, 0 deletions

diff --git a/llvm/unittests/Support/raw_ostream_test.cpp b/llvm/unittests/Support/raw_ostream_test.cpp
index f87d2f60d16..777e555949e 100644
--- a/llvm/unittests/Support/raw_ostream_test.cpp
+++ b/llvm/unittests/Support/raw_ostream_test.cpp
@@ -9,6 +9,7 @@
 
 #include "gtest/gtest.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -330,4 +331,11 @@ TEST(raw_ostreamTest, FormattedHexBytes) {
             "0007: 68 69 6a 6b 6c        |hijkl|",
             format_bytes_with_ascii_str(B.take_front(12), 0, 7, 1));
 }
+
+TEST(raw_fd_ostreamTest, multiple_raw_fd_ostream_to_stdout) {
+  std::error_code EC;
+
+  { raw_fd_ostream("-", EC, sys::fs::OpenFlags::F_None); }
+  { raw_fd_ostream("-", EC, sys::fs::OpenFlags::F_None); }
+}
 }