From 6c50d155625d83bde35dc78bc6920c9795462d58 Mon Sep 17 00:00:00 2001
From: Bart Schaefer <schaefer@zsh.org>
Date: Sat, 24 Feb 2024 21:16:15 -0800
Subject: 52597: fix character counts in context of operator and operand errors

---
 ChangeLog  |  3 +++
 Src/math.c | 25 ++++++++++++++++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9f7289cea..684820f92 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2024-02-24  Bart Schaefer  <schaefer@zsh.org>
 
+	* 52597: Src/math.c: fix multibyte and metafied character counts
+	when providing context for operator and operand errors
+
 	* 52596: Src/exec.c: metafy interpreter name for error message
 
 	* Stephane: 52591: Src/builtin.c: printf builtin must pass
diff --git a/Src/math.c b/Src/math.c
index 50b69d6a1..d97dae238 100644
--- a/Src/math.c
+++ b/Src/math.c
@@ -1557,21 +1557,32 @@ checkunary(int mtokc, char *mptr)
 	    errmsg = 2;
     }
     if (errmsg) {
-	int len, over = 0;
+	int len = 0, over = 0;
 	char *errtype = errmsg == 2 ? "operator" : "operand";
 	while (inblank(*mptr))
 	    mptr++;
-	len = ztrlen(mptr);
-	if (len > 10) {
-	    len = 10;
-	    over = 1;
+	if (isset(MULTIBYTE))
+	    MB_CHARINIT();
+	while (over < 10 && mptr[len]) {
+	    if (isset(MULTIBYTE))
+		len += MB_METACHARLEN(mptr+len);
+	    else
+		len += (mptr[len] == Meta ? 2 : 1);
+	    ++over;
+	}
+	if ((over = mptr[len])) {
+	    mptr = dupstring(mptr);
+	    if (mptr[len] == Meta)
+		mptr[len+1] = 0;
+	    else
+		mptr[len] = 0;
 	}
 	if (!*mptr)
 	    zerr("bad math expression: %s expected at end of string",
 		errtype);
 	else
-	    zerr("bad math expression: %s expected at `%l%s'",
-		 errtype, mptr, len, over ? "..." : "");
+	    zerr("bad math expression: %s expected at `%s%s'",
+		 errtype, mptr, over ? "..." : "");
     }
     unary = !(tp & OP_OPF);
 }
-- 
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