--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/flang/runtime/io-error.cpp	Mon May 25 11:55:54 2020 +0900
@@ -0,0 +1,108 @@
+//===-- runtime/io-error.cpp ------------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "io-error.h"
+#include "config.h"
+#include "magic-numbers.h"
+#include "tools.h"
+#include <cerrno>
+#include <cstdarg>
+#include <cstdio>
+#include <cstring>
+
+namespace Fortran::runtime::io {
+
+void IoErrorHandler::Begin(const char *sourceFileName, int sourceLine) {
+  flags_ = 0;
+  ioStat_ = 0;
+  ioMsg_.reset();
+  SetLocation(sourceFileName, sourceLine);
+}
+
+void IoErrorHandler::SignalError(int iostatOrErrno, const char *msg, ...) {
+  if (iostatOrErrno == IostatEnd && (flags_ & hasEnd)) {
+    if (!ioStat_ || ioStat_ < IostatEnd) {
+      ioStat_ = IostatEnd;
+    }
+  } else if (iostatOrErrno == IostatEor && (flags_ & hasEor)) {
+    if (!ioStat_ || ioStat_ < IostatEor) {
+      ioStat_ = IostatEor; // least priority
+    }
+  } else if (iostatOrErrno != IostatOk) {
+    if (flags_ & (hasIoStat | hasErr)) {
+      if (ioStat_ <= 0) {
+        ioStat_ = iostatOrErrno; // priority over END=/EOR=
+        if (msg && (flags_ & hasIoMsg)) {
+          char buffer[256];
+          va_list ap;
+          va_start(ap, msg);
+          std::vsnprintf(buffer, sizeof buffer, msg, ap);
+          ioMsg_ = SaveDefaultCharacter(buffer, std::strlen(buffer) + 1, *this);
+        }
+      }
+    } else if (msg) {
+      va_list ap;
+      va_start(ap, msg);
+      CrashArgs(msg, ap);
+    } else if (const char *errstr{IostatErrorString(iostatOrErrno)}) {
+      Crash(errstr);
+    } else {
+      Crash("I/O error (errno=%d): %s", iostatOrErrno,
+          std::strerror(iostatOrErrno));
+    }
+  }
+}
+
+void IoErrorHandler::SignalError(int iostatOrErrno) {
+  SignalError(iostatOrErrno, nullptr);
+}
+
+void IoErrorHandler::SignalErrno() { SignalError(errno); }
+
+void IoErrorHandler::SignalEnd() { SignalError(IostatEnd); }
+
+void IoErrorHandler::SignalEor() { SignalError(IostatEor); }
+
+bool IoErrorHandler::GetIoMsg(char *buffer, std::size_t bufferLength) {
+  const char *msg{ioMsg_.get()};
+  if (!msg) {
+    msg = IostatErrorString(ioStat_);
+  }
+  if (msg) {
+    ToFortranDefaultCharacter(buffer, bufferLength, msg);
+    return true;
+  }
+
+  char *newBuf;
+  // Following code is taken from llvm/lib/Support/Errno.cpp
+  // in LLVM v9.0.1
+#if HAVE_STRERROR_R
+  // strerror_r is thread-safe.
+#if defined(__GLIBC__) && defined(_GNU_SOURCE)
+  // glibc defines its own incompatible version of strerror_r
+  // which may not use the buffer supplied.
+  newBuf = ::strerror_r(ioStat_, buffer, bufferLength);
+#else
+  return ::strerror_r(ioStat_, buffer, bufferLength) == 0;
+#endif
+#elif HAVE_DECL_STRERROR_S // "Windows Secure API"
+  return ::strerror_s(buffer, bufferLength, ioStat_) == 0;
+#elif HAVE_STRERROR
+  // Copy the thread un-safe result of strerror into
+  // the buffer as fast as possible to minimize impact
+  // of collision of strerror in multiple threads.
+  newBuf = strerror(ioStat_);
+#else
+  // Strange that this system doesn't even have strerror
+  return false;
+#endif
+  ::strncpy(buffer, newBuf, bufferLength - 1);
+  buffer[bufferLength - 1] = '\n';
+  return true;
+}
+} // namespace Fortran::runtime::io