1 files changed, 19 insertions, 12 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index 6142a244c..66b040b31 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -1477,7 +1477,6 @@ static int writeCon_utf8(int fd, const char *u8buf, size_t u8siz)
                 while (c & (0x80 >> topbits))
                         ++topbits;
 
-        process_byte:
                 if (state == 0 && topbits == 0) {
                         // valid ASCII7, state remains 0
                         codepoint = c;
@@ -1494,18 +1493,26 @@ static int writeCon_utf8(int fd, const char *u8buf, size_t u8siz)
                         state = topbits - 1;  // remaining bytes after lead
                         continue;
 
-                } else if (state >= 0) {
-                        // invalid byte at state 0/1/2/3, add placeholder once
-                        codepoint = CONFIG_SUBST_WCHAR;
-                        state = -1;
-
                 } else {
-                        // inside bad sequence (placeholder char already added)
-                        if (topbits == 1 || topbits > 4)
-                                continue;  // still bad
-                        // c is valid for state 0, process it with clean slate
-                        state = 0;
-                        goto process_byte;
+                        // already bad (state<0), or unexpected c at state 0-3.
+                        // placeholder is added only at the 1st (state>=0).
+                        // regardless, c may be valid to reprocess as state 0
+                        // (even when it's the 1st unexpected in state 1/2/3)
+                        int placeholder_done = state < 0;
+
+                        if (topbits < 5 && topbits != 1) {
+                                --u8buf;  // valid for state 0, reprocess
+                                ++u8siz;
+                                state = 0;
+                        } else {
+                                state = -1;  // set/keep bad state
+                        }
+
+                        if (placeholder_done)
+                                continue;
+
+                        // 1st unexpected char, add placeholder
+                        codepoint = CONFIG_SUBST_WCHAR;
                 }
 
                 // codepoint is complete