Added a comment.
The structs for stdin/stdout/stderr are formed with a static initializer
that needs to be updated if something in FILE is changed.
diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index 79e526b..791b260 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -112,6 +112,9 @@
* that does not match the previous one in _bf. When this happens,
* _ub._base becomes non-nil (i.e., a stream has ungetc() data iff
* _ub._base!=NULL) and _up and _ur save the current values of _p and _r.
+ *
+ * NOTE: if you change this structure, you also need to update the
+ * std() initializer in findfp.c.
*/
typedef struct __sFILE {
unsigned char *_p; /* current position in (some) buffer */