Fix ungetwc for multi byte chars

src/header/wchar/mod.rs

@@ -280,8 +280,15 @@ pub unsafe extern "C" fn ungetwc(wc: wint_t, stream: &mut FILE) -> wint_t {
     if amount == usize::MAX {
         return WEOF;
     }
+
+    /* 
+    We might have unget multiple bytes for a single wchar, eg, `ç` is [195, 167]. 
+    We need to unget them in reversed, so they are pused as [..., 167, 195, ...]
+    When we do fgetwc, we pop from the Vec, getting the write order of bytes [195, 167].
+    If we called ungetc in the non-reversed order, we would get [167, 195]
+    */
     for i in 0..amount {
-        ungetc(bytes[i] as c_int, &mut *stream);
+        ungetc(bytes[amount - 1 - i] as c_int, &mut *stream);
     }
 
     wc

tests/Makefile

@@ -103,6 +103,7 @@ EXPECT_NAMES=\
 	unistd/swab \
 	unistd/write \
 	waitpid \
+	wchar/fgetwc \
 	wchar/fwide \
 	wchar/mbrtowc \
 	wchar/mbsrtowcs \

tests/wchar/ungetwc.c

@@ -3,9 +3,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
- 
+#include <locale.h>
+
 int main()
 {
+   setlocale(LC_ALL, "");
    FILE *stream;
    wint_t wc;
    wint_t wc2;

tests/wchar/ungetwc.in

@@ -1 +1 @@
-123A
+123çA