n-api: provide node::FatalError() when internals are absent

src/node_api.cc must build both as a part of node and as an addon
against an older version of node, so that it may be possible to make
N-API available on older, already-published versions of node. Thus,
it must not make use of node internals such as node::FatalError().

Yet N-API must also exit with a fatal error in the absence of a
napi_env pointer. To that end, node::FatalError() is implemented if
internals are unavailable by copying PrintErrorString() from node.cc,
simplifying it to accept only a location and an error message, and
augmenting it with fflush() and platform-ifdefed abort(), the latter
two of which are also copied from node.cc.

Re nodejs#232
Re https://github.com/nodejs/node-api

src/node_api.cc

@@ -17,6 +17,56 @@
 #include "node_api.h"
 #include "env-inl.h"
 
+// If we're outside of node we must implement node::FatalError() ourselves
+#if not defined(NODE_WANT_INTERNALS) || !NODE_WANT_INTERNALS
+
+// Copied and simplified from node.cc
+namespace node {
+
+void FatalError(const char* location, const char *error) {
+  const char *format = "FATAL ERROR: %s %s\n";
+#ifdef _WIN32
+  HANDLE stderr_handle = GetStdHandle(STD_ERROR_HANDLE);
+
+  // Check if stderr is something other than a tty/console
+  if (stderr_handle == INVALID_HANDLE_VALUE ||
+      stderr_handle == nullptr ||
+      uv_guess_handle(_fileno(stderr)) != UV_TTY) {
+    fprintf(stderr, format, location, error);
+    return;
+  }
+
+  // Fill in any placeholders
+  int n = _scprintf(format, location, error);
+  std::vector<char> out(n + 1);
+  sprintf(out.data(), format, location, error);
+
+  // Get required wide buffer size
+  n = MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, nullptr, 0);
+
+  std::vector<wchar_t> wbuf(n);
+  MultiByteToWideChar(CP_UTF8, 0, out.data(), -1, wbuf.data(), n);
+
+  // Don't include the null character in the output
+  CHECK_GT(n, 0);
+  WriteConsoleW(stderr_handle, wbuf.data(), n - 1, nullptr, nullptr);
+#else
+  fprintf(stderr, format, location, error);
+#endif
+
+  fflush(stderr);
+
+  // Windows 8+ does not like abort() in Release mode
+#ifdef _WIN32
+  raise(SIGABRT);
+#else
+  abort();
+#endif
+}
+
+} // namespace node
+#endif // internals unavailable or unwanted
+
 static
 napi_status napi_set_last_error(napi_env env, napi_status error_code,
                                 uint32_t engine_error_code = 0,