+ ASSERT (fgetc (fp) == 'f');
+ ASSERT (freading (fp));
+ ASSERT (fseek (fp, 2, SEEK_CUR) == 0);
+ /* freading (fp) is undefined here, but fwriting (fp) is false. */
+ ASSERT (fgetc (fp) == 'b');
+ ASSERT (freading (fp));
+ fflush (fp);
+ /* freading (fp) is undefined here, but fwriting (fp) is false. */
+ ASSERT (fgetc (fp) == 'x');
+ ASSERT (freading (fp));
+ /* This fseek call is necessary when switching from reading to writing.
+ See the description of fopen(), ISO C 99 7.19.5.3.(6). */
+ ASSERT (fseek (fp, 0, SEEK_CUR) == 0);
+ /* freading (fp) is undefined here, but fwriting (fp) is false. */
+ ASSERT (fputc ('z', fp) == 'z');
+ ASSERT (!freading (fp));
+ ASSERT (fseek (fp, 0, SEEK_END) == 0);
+ /* freading (fp) is undefined here, because on some implementations (e.g.
+ glibc) fseek causes a buffer to be read.
+ fwriting (fp) is undefined as well. */
+ ASSERT (fclose (fp) == 0);