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      // RUN: %clangxx -g %s -o %t && %run %t
#include <assert.h>
#include <stdio.h>
int main(int argc, char **argv) {
  FILE *fp = fopen(argv[0], "r");
  assert(fp);
  // the file should be at least one character long, always
  assert(getc_unlocked(fp) != EOF);
  // POSIX guarantees being able to ungetc() at least one character
  // NB: ungetc_unlocked is apparently not present
  assert(ungetc('X', fp) != EOF);
  // check whether ungetc() works with getc_unlocked()
  assert(getc_unlocked(fp) == 'X');
  assert(!fclose(fp));
  return 0;
}
 
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