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carbon-lang/common/vlog_internal.h
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2023-02-02 17:43:10 -08:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#ifndef CARBON_COMMON_VLOG_INTERNAL_H_
#define CARBON_COMMON_VLOG_INTERNAL_H_
#include <cstdlib>
#include "llvm/Support/raw_ostream.h"
namespace Carbon::Internal {
// Wraps a stream and exiting for fatal errors. Should only be used by check.h
// macros.
class VLoggingStream {
public:
// Internal type used in macros to dispatch to the `operator|` overload.
struct Helper {};
explicit VLoggingStream(llvm::raw_ostream* stream)
// Prefix the buffer with the current bug report message.
: stream_(stream) {}
~VLoggingStream() = default;
// If the bool cast occurs, it's because the condition is false. This supports
// && short-circuiting the creation of ExitingStream.
explicit operator bool() const { return true; }
// Forward output to llvm::errs.
template <typename T>
auto operator<<(const T& message) -> VLoggingStream& {
*stream_ << message;
return *this;
}
// Low-precedence binary operator overload used in vlog.h macros.
friend auto operator|(Helper /*helper*/, VLoggingStream& /*stream*/) -> void {
}
private:
[[noreturn]] auto Done() -> void;
llvm::raw_ostream* stream_;
};
} // namespace Carbon::Internal
// Raw logging stream. This should be used when building forms of vlog
// macros.
#define CARBON_VLOG_INTERNAL_STREAM(stream) \
Carbon::Internal::VLoggingStream::Helper() | \
Carbon::Internal::VLoggingStream(stream)
#endif // CARBON_COMMON_VLOG_INTERNAL_H_