Fix garbled problem with msg_puts_printf on Windows

src/nvim/message.c

@@ -2303,18 +2303,19 @@ int msg_use_printf(void)
 static void msg_puts_printf(const char *str, const ptrdiff_t maxlen)
 {
   const char *s = str;
-  char buf[4];
+  char buf[7];
   char *p;
 
   while ((maxlen < 0 || s - str < maxlen) && *s != NUL) {
+    int len = utf_ptr2len((const char_u *)s);
     if (!(silent_mode && p_verbose == 0)) {
       // NL --> CR NL translation (for Unix, not for "--version")
       p = &buf[0];
       if (*s == '\n' && !info_message) {
         *p++ = '\r';
       }
-      *p++ = *s;
-      *p = '\0';
+      memcpy(p, s, len);
+      *(p + len) = '\0';
       if (info_message) {
         mch_msg(buf);
       } else {
@@ -2323,20 +2324,21 @@ static void msg_puts_printf(const char *str, const ptrdiff_t maxlen)
     }
 
     // primitive way to compute the current column
+    int cw = utf_char2cells(utf_ptr2char((const char_u *)s));
     if (cmdmsg_rl) {
       if (*s == '\r' || *s == '\n') {
         msg_col = Columns - 1;
       } else {
-        msg_col--;
+        msg_col -= cw;
       }
     } else {
       if (*s == '\r' || *s == '\n') {
         msg_col = 0;
       } else {
-        msg_col++;
+        msg_col += cw;
       }
     }
-    s++;
+    s += len;
   }
   msg_didout = true;  // assume that line is not empty
 }

src/nvim/vim.h

@@ -35,6 +35,10 @@ enum { NUMBUFLEN = 65 };
 
 #include "nvim/gettext.h"
 
+#ifdef WIN32
+# include "nvim/mbyte.h"  // for utf8_to_utf16
+#endif
+
 // special attribute addition: Put message in history
 #define MSG_HIST                0x1000
 
@@ -287,9 +291,34 @@ enum { FOLD_TEXT_LEN = 51 };  //!< buffer size for get_foldtext()
 // functions of these names. The declarations would break if the defines had
 // been seen at that stage.  But it must be before globals.h, where error_ga
 // is declared.
-#define mch_errmsg(str)        fprintf(stderr, "%s", (str))
+#ifdef WIN32
+# define mch_errmsg(str) \
+  do { \
+    wchar_t *utf16str; \
+    int conversion_result = utf8_to_utf16((str), &utf16str); \
+    if (conversion_result != 0) { \
+      EMSG2("utf8_to_utf16 failed: %d", conversion_result); \
+    } else { \
+      fwprintf(stderr, L"%ls", utf16str); \
+      xfree(utf16str); \
+    } \
+  } while (0)
+# define mch_msg(str) \
+  do { \
+    wchar_t *utf16str; \
+    int conversion_result = utf8_to_utf16((str), &utf16str); \
+    if (conversion_result != 0) { \
+      EMSG2("utf8_to_utf16 failed: %d", conversion_result); \
+    } else { \
+      wprintf(L"%ls", utf16str); \
+      xfree(utf16str); \
+    } \
+  } while (0)
+#else
+# define mch_errmsg(str)        fprintf(stderr, "%s", (str))
+# define mch_msg(str)           printf("%s", (str))
+#endif
 #define display_errors()       fflush(stderr)
-#define mch_msg(str)           printf("%s", (str))
 
 #include "nvim/globals.h"        // global variables and messages
 #include "nvim/buffer_defs.h"    // buffer and windows