impl some file operations

rc_includes/stdio.h

@@ -0,0 +1,22 @@
+#ifndef STDIO_H
+#define STDIO_H
+#include <stdlib.h>
+
+typedef struct _iobuf {
+  char *_ptr;
+  int _cnt;
+  char *_base;
+  int _flag;
+  int _file;
+  int _charbuf;
+  int _bufsiz;
+  char *_tmpfname;
+} FILE;
+
+FILE *fopen(const char *filename, const char *mode);
+int fclose(FILE *stream);
+size_t fwrite(const void *ptr, size_t size, size_t count, FILE *stream);
+size_t fread(void *ptr, size_t size, size_t count, FILE *stream);
+int printf(const char *format, ...);
+
+#endif // STDIO_H

rc_includes/stdlib.h

@@ -0,0 +1,6 @@
+#ifndef STDLIB_H
+#define STDLIB_H
+
+typedef int size_t;
+
+#endif // STDLIB_H

test.c

@@ -1,15 +1,7 @@
-#include <stdarg.h>
+#include <stdio.h>
 
-int sum(int num, ...) {
-  int res = 0;
-  va_list args;
-  va_start(args, num);
-  int i;
-  for (i = 0; i < num; i++) {
-    res += va_arg(args, int);
-  }
-  va_end(args);
-  return res;
+int main() {
+  FILE *f = fopen("test.txt", "w");
+  fwrite("Hello, World!\n", 1, 14, f);
+  fclose(f);
 }
-
-int main() { return sum(10, 20, 30); }