tinystdio: ungetc decrements file position indicator correctly

According to the ISO/IEC_9899_1999, section: J.5.16 it is mentioned that there is a file position indicator that is decremented by each call of the ungetc function.

The value of the file position indicator was not directed to the right position, this issue is now handled in the ftell function
so the file indicator is placed correctly after the function
ungetc is called.
An "if" condition is added which checks on the value of unget and if it is not equal zero then ungetc function is called so the indicator will be decremented.

Signed-off-by: Hana Ashour <[email protected]>

Author: HanaMAshour

newlib/libc/tinystdio/ftell.c

@@ -43,8 +43,14 @@ FSEEK_TYPE
 ftell(FILE *stream)
 {
         struct __file_ext *xf = (struct __file_ext *) stream;
-        if ((stream->flags & __SEXT) && xf->seek)
-                return (FSEEK_TYPE) (xf->seek) (stream, 0, SEEK_CUR);
+        FSEEK_TYPE ret;
+        if ((stream->flags & __SEXT) && xf->seek) {
+                ret = (FSEEK_TYPE) (xf->seek) (stream, 0, SEEK_CUR);
+                if(stream->unget != 0)
+                        return --ret;
+                else
+                        return ret;
+        }
         errno = ESPIPE;
 	return -1;
 }