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llvm-mirror/lib/Support/ToolOutputFile.cpp
Pavel Labath 0d0270ebc8 [Support] Use outs() in ToolOutputFile
Summary:
If the output filename was specified as "-", the ToolOutputFile class
would create a brand new raw_ostream object referring to the stdout.
This patch changes it to reuse the llvm::outs() singleton.

At the moment, this change should be "NFC", but it does enable other
enhancements, like the automatic stdout/stderr synchronization as
discussed on D80803.

I've checked the history, and I did not find any indication that this
class *has* to use a brand new stream object instead of outs() --
indeed, it is special-casing "-" in a number of places already, so this
change fits the pattern pretty well. I suspect the main reason for the
current state of affairs is that the class was originally introduced
(r111595, in 2010) as a raw_fd_ostream subclass, which made any other
solution impossible.

Another potential benefit of this patch is that it makes it possible to
move the raw_ostream class out of the business of special-casing "-" for
stdout handling. That state of affairs does not seem appropriate because
"-" is a valid filename (albeit hard to access with a lot of command
line tools) on most systems. Handling "-" in ToolOutputFile seems more
appropriate.

To make this possible, this patch changes the return type of
llvm::outs() and errs() to raw_fd_ostream&. Previously the functions
were constructing objects of that type, but returning a generic
raw_ostream reference. This makes it possible for new ToolOutputFile and
other code to use raw_fd_ostream methods like error() on the outs()
object. This does not seem like a bad thing (since stdout is a file
descriptor which can be redirected to anywhere, it makes sense to ask it
whether the writing was successful or if it supports seeking), and
indeed a lot of code was already depending on this fact via the
ToolOutputFile "back door".

Reviewers: dblaikie, JDevlieghere, MaskRay, jhenderson

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81078
2020-06-04 14:56:35 +02:00

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//===--- ToolOutputFile.cpp - Implement the ToolOutputFile class --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This implements the ToolOutputFile class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Signals.h"
using namespace llvm;
static bool isStdout(StringRef Filename) { return Filename == "-"; }
ToolOutputFile::CleanupInstaller::CleanupInstaller(StringRef Filename)
: Filename(std::string(Filename)), Keep(false) {
// Arrange for the file to be deleted if the process is killed.
if (!isStdout(Filename))
sys::RemoveFileOnSignal(Filename);
}
ToolOutputFile::CleanupInstaller::~CleanupInstaller() {
if (isStdout(Filename))
return;
// Delete the file if the client hasn't told us not to.
if (!Keep)
sys::fs::remove(Filename);
// Ok, the file is successfully written and closed, or deleted. There's no
// further need to clean it up on signals.
sys::DontRemoveFileOnSignal(Filename);
}
ToolOutputFile::ToolOutputFile(StringRef Filename, std::error_code &EC,
sys::fs::OpenFlags Flags)
: Installer(Filename) {
if (isStdout(Filename)) {
OS = &outs();
EC = std::error_code();
return;
}
OSHolder.emplace(Filename, EC, Flags);
OS = OSHolder.getPointer();
// If open fails, no cleanup is needed.
if (EC)
Installer.Keep = true;
}
ToolOutputFile::ToolOutputFile(StringRef Filename, int FD)
: Installer(Filename) {
OSHolder.emplace(FD, true);
OS = OSHolder.getPointer();
}