/// \p Flags allows optional flags to control how the file will be opened.
///
/// As a special case, if Filename is "-", then the stream will use
- /// STDOUT_FILENO instead of opening a file. Note that it will still consider
- /// itself to own the file descriptor. In particular, it will close the
- /// file descriptor when it is done (this is necessary to detect
- /// output errors).
+ /// STDOUT_FILENO instead of opening a file. This will not close the stdout
+ /// descriptor.
raw_fd_ostream(StringRef Filename, std::error_code &EC,
sys::fs::OpenFlags Flags);
/// FD is the file descriptor that this writes to. If ShouldClose is true,
- /// this closes the file when the stream is destroyed.
+ /// this closes the file when the stream is destroyed. If FD is for stdout or
+ /// stderr, it will not be closed.
raw_fd_ostream(int fd, bool shouldClose, bool unbuffered=false);
~raw_fd_ostream() override;
ShouldClose = false;
return;
}
- // We do not want to close STDOUT as there may have been several uses of it
- // such as the case: llc %s -o=- -pass-remarks-output=- -filetype=asm
- // which cause multiple closes of STDOUT_FILENO and/or use-after-close of it.
- // Using dup() in getFD doesn't work as we end up with original STDOUT_FILENO
- // open anyhow.
+
+ // Do not attempt to close stdout or stderr. We used to try to maintain the
+ // property that tools that support writing file to stdout should not also
+ // write informational output to stdout, but in practice we were never able to
+ // maintain this invariant. Many features have been added to LLVM and clang
+ // (-fdump-record-layouts, optimization remarks, etc) that print to stdout, so
+ // users must simply be aware that mixed output and remarks is a possibility.
if (FD <= STDERR_FILENO)
ShouldClose = false;
/// outs() - This returns a reference to a raw_ostream for standard output.
/// Use it like: outs() << "foo" << "bar";
raw_ostream &llvm::outs() {
- // Set buffer settings to model stdout behavior. Delete the file descriptor
- // when the program exits, forcing error detection. This means that if you
- // ever call outs(), you can't open another raw_fd_ostream on stdout, as we'll
- // close stdout twice and print an error the second time.
+ // Set buffer settings to model stdout behavior.
std::error_code EC;
static raw_fd_ostream S("-", EC, sys::fs::F_None);
assert(!EC);