set stream orientations in open_[w]memstream

fundamentally there is no good reason these functions need to set an
orientation (morally it should be possible to write a wchar_t[] memory
stream using byte functions, or a char[] memory stream using wide
functions), but it's a part of the specification that they do. aside
from being able to inspect the orientation with fwide, failure to set
the orientation in open_wmemstream is observable if the locale changes
between open_wmemstream and the first operation on the stream; this is
because the encoding rule (locale) for the stream is required to be
bound at the time the stream becomes wide-oriented.

for open_wmemstream, call fwide to avoid duplicating the logic for
binding the encoding rule. for open_memstream it suffices just to set
the mode field in the FILE struct.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/stdio/open_wmemstream.c b/src/stdio/open_wmemstream.c
index cb693ea7..a7c3a645 100644
--- a/src/stdio/open_wmemstream.c
+++ b/src/stdio/open_wmemstream.c
@@ -94,5 +94,7 @@ FILE *open_wmemstream(wchar_t **bufp, size_t *sizep)
 
 	if (!libc.threaded) f->f.lock = -1;
 
+	fwide(&f->f, 1);
+
 	return __ofl_add(&f->f);
 }