Add ESP8266 RTOS example

PUBLISHED_FROM=892d01b09f5801d3d19e6db1ce22b7916d2f83d5

examples/ESP8266_RTOS/user/esp_libc.c

@@ -0,0 +1,54 @@
+/*
+* Copyright (c) 2015 Cesanta Software Limited
+* All rights reserved
+*/
+
+#include <ctype.h>
+#include <sys/time.h>
+#include <stdint.h>
+
+#include <math.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "esp_common.h"
+
+/* Makes fprintf(stdout) and stderr work. */
+_ssize_t _write_r(struct _reent *r, int fd, void *buf, size_t len) {
+  if (fd == 1 || fd == 2) {
+    size_t i;
+    for (i = 0; i < len; i++) {
+      os_putc(((char *) buf)[i]);
+    }
+    return len;
+  }
+  return -1;
+}
+
+/*
+ * You'll need to implement _open_r and friends if you want file operations. See
+ * https://github.com/cesanta/smart.js/blob/master/platforms/esp8266/user/esp_fs.c
+ * for SPIFFS-based implementation.
+ */
+
+void abort(void) __attribute__((no_instrument_function));
+void abort(void) {
+  /* cause an unaligned access exception, that will drop you into gdb */
+  *(int *) 1 = 1;
+  while (1)
+    ; /* avoid gcc warning because stdlib abort() has noreturn attribute */
+}
+
+void _exit(int status) {
+  printf("_exit(%d)\n", status);
+  abort();
+}
+
+int _gettimeofday_r(struct _reent *r, struct timeval *tp, void *tzp) {
+  uint32_t time = system_get_time();
+  tp->tv_sec = time / 1000000;
+  tp->tv_usec = time % 1000000;
+  return 0;
+}