1 files changed, 61 insertions, 0 deletions
diff --git a/libio/bug-ungetc.c b/libio/bug-ungetc.c
new file mode 100644
index 0000000000..51940b68f5
--- /dev/null
+++ b/libio/bug-ungetc.c
@@ -0,0 +1,61 @@
+/* Test program for ungetc/ftell interaction bug.  */
+
+#include <stdio.h>
+
+static void do_prepare (void);
+#define PREPARE(argc, argv) do_prepare ()
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static const char pattern[] = "12345";
+static char *temp_file;
+
+static void
+do_prepare (void)
+{
+  int fd = create_temp_file ("bug-ungetc.", &temp_file);
+  if (fd == -1)
+    {
+      printf ("cannot create temporary file: %m\n");
+      exit (1);
+    }
+  write (fd, pattern, sizeof (pattern));
+  close (fd);
+}
+
+static int
+do_test (void)
+{
+  int i;
+  FILE *f;
+  char buf[10];
+  long offset, diff;
+  int result = 0;
+
+  f = fopen (temp_file, "rw");
+
+  rewind (f);
+  for (i = 0; i < 3; i++)
+    printf ("%c\n", getc (f));
+  offset = ftell (f);
+  printf ("offset = %ld\n", offset);
+  if (ungetc ('4', f) != '4')
+    {
+      printf ("ungetc failed\n");
+      abort ();
+    }
+  printf ("offset after ungetc = %ld\n", ftell (f));
+
+  i = fread ((void *) buf, 4, (size_t) 1, f);
+  printf ("read %d (%c), offset = %ld\n", i, buf[0], ftell (f));
+  diff = ftell (f) - offset;
+  if (diff != 3)
+    {
+      printf ("ftell did not update properly.  got %ld, expected 3\n", diff);
+      result = 1;
+    }
+  fclose (f);
+
+  return result;
+}