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-rw-r--r--libio/bug-ungetc.c61
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;
+}