src/c_api/c_api_error.cc

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*!
 *  Copyright (c) 2015 by Contributors
 * \file c_api_error.cc
 * \brief C error handling
 */
#include <nnvm/c_api.h>
#include "./c_api_common.h"

#ifndef _LIBCPP_SGX_NO_IOSTREAMS
//--------------------------------------------------------
// Error handling mechanism
// -------------------------------------------------------
// Standard error message format, {} means optional
//--------------------------------------------------------
// {error_type:} {message0}
// {message1}
// {message2}
// {Stack trace:}    // stack traces follow by this line
//   {trace 0}       // two spaces in the begining.
//   {trace 1}
//   {trace 2}
//--------------------------------------------------------
/*!
 * \brief Normalize error message
 *
 *  Parse them header generated by by LOG(FATAL) and CHECK
 *  and reformat the message into the standard format.
 *
 *  This function will also merge all the stack traces into
 *  one trace and trim them.
 *
 * \param err_msg The error message.
 * \return normalized message.
 */
std::string NormalizeError(std::string err_msg) {
  // ------------------------------------------------------------------------
  // log with header, {} indicates optional
  //-------------------------------------------------------------------------
  // [timestamp] file_name:line_number: {check_msg:} {error_type:} {message0}
  // {message1}
  // Stack trace:
  //   {stack trace 0}
  //   {stack trace 1}
  //-------------------------------------------------------------------------
  // Normalzied version
  //-------------------------------------------------------------------------
  // error_type: check_msg message0
  // {message1}
  // Stack trace:
  //   File file_name, line lineno
  //   {stack trace 0}
  //   {stack trace 1}
  //-------------------------------------------------------------------------
  int line_number = 0;
  std::istringstream is(err_msg);
  std::string line, file_name, error_type, check_msg;

  // Parse log header and set the fields,
  // Return true if it the log is in correct format,
  // return false if something is wrong.
  auto parse_log_header = [&]() {
    // skip timestamp
    if (is.peek() != '[') {
      getline(is, line);
      return true;
    }
    if (!(is >> line)) return false;
    // get filename
    while (is.peek() == ' ') is.get();
    if (!getline(is, file_name, ':')) {
      return false;
    } else {
      if (is.peek() == '\\' || is.peek() == '/') {
        // windows path
        if (!getline(is, line, ':')) return false;
        file_name = file_name + ':' + line;
      }
    }
    // get line number
    if (!(is >> line_number)) return false;
    // get rest of the message.
    while (is.peek() == ' ' || is.peek() == ':') is.get();
    if (!getline(is, line)) return false;
    // detect check message, rewrite to remote extra :
    if (line.compare(0, 13, "Check failed:") == 0) {
      size_t end_pos = line.find(':', 13);
      if (end_pos == std::string::npos) return false;
      check_msg = line.substr(0, end_pos + 1) + ' ';
      line = line.substr(end_pos + 1);
    }
    return true;
  };
  // if not in correct format, do not do any rewrite.
  if (!parse_log_header()) return err_msg;
  // Parse error type.
  {
    size_t start_pos = 0, end_pos;
    for (; start_pos < line.length() && line[start_pos] == ' '; ++start_pos) {}
    for (end_pos = start_pos; end_pos < line.length(); ++end_pos) {
      char ch = line[end_pos];
      if (ch == ':') {
        error_type = line.substr(start_pos, end_pos - start_pos);
        break;
      }
      // [A-Z0-9a-z_.]
      if (!std::isalpha(ch) && !std::isdigit(ch) && ch != '_' && ch != '.') break;
    }
    if (error_type.length() != 0) {
      // if we successfully detected error_type: trim the following space.
      for (start_pos = end_pos + 1;
           start_pos < line.length() && line[start_pos] == ' '; ++start_pos) {}
      line = line.substr(start_pos);
    } else {
      // did not detect error_type, use default value.
      line = line.substr(start_pos);
      error_type = "MXNetError";
    }
  }
  // Seperate out stack trace.
  std::ostringstream os;
  os << error_type << ": " << check_msg << line << '\n';

  bool trace_mode = true;
  std::vector<std::string> stack_trace;
  while (getline(is, line)) {
    if (trace_mode) {
      if (line.compare(0, 2, "  ") == 0) {
        stack_trace.push_back(line);
      } else {
        trace_mode = false;
        // remove EOL trailing stacktrace.
        if (line.length() == 0) continue;
      }
    }
    if (!trace_mode) {
      if (line.compare(0, 11, "Stack trace") == 0) {
        trace_mode = true;
      } else {
        os << line << '\n';
      }
    }
  }
  if (stack_trace.size() != 0 || file_name.length() != 0) {
    os << "Stack trace:\n";
    if (file_name.length() != 0) {
      os << "  File \"" << file_name << "\", line " << line_number << "\n";
    }
    // Print out stack traces, optionally trim the c++ traces
    // about the frontends (as they will be provided by the frontends).
    bool ffi_boundary = false;
    for (const auto& line : stack_trace) {
      // Heuristic to detect python ffi.
      if (line.find("libffi.so") != std::string::npos ||
          line.find("core.cpython") != std::string::npos) {
        ffi_boundary = true;
      }
      // If the backtrace is not c++ backtrace with the prefix "  [bt]",
      // then we can stop trimming.
      if (ffi_boundary && line.compare(0, 6, "  [bt]") != 0) {
        ffi_boundary = false;
      }
      if (!ffi_boundary) {
        os << line << '\n';
      }
    }
  }
  return os.str();
}

#else
std::string NormalizeError(std::string err_msg) {
  return err_msg;
}
#endif

int MXAPIHandleException(const std::exception &e) {
  MXAPISetLastError(NormalizeError(e.what()).c_str());
  return -1;
}

const char *MXGetLastError() {
  return NNGetLastError();
}

void MXAPISetLastError(const char* msg) {
  NNAPISetLastError(msg);
}