Fix rb_enc_left_char_head()

eregon · eregon · commit 4d17ba42c1ef · 2023-09-20T10:29:09.000+02:00
* Fixes #3267
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,7 @@ New features:
 
 Bug fixes:
 
+* Fix `rb_enc_left_char_head()` so it is not always `ArgumentError` (#3267, @eregon).
 
 Compatibility:
 
diff --git a/lib/cext/ABI_check.txt b/lib/cext/ABI_check.txt
@@ -1 +1 @@
-4
+5
diff --git a/src/main/c/cext/encoding.c b/src/main/c/cext/encoding.c
@@ -226,7 +226,10 @@ int rb_enc_get_index(VALUE obj) {
 }
 
 char* rb_enc_left_char_head(const char *start, const char *p, const char *end, rb_encoding *enc) {
-  int length = start - end;
+  if (p <= start || p >= end) {
+    return p;
+  }
+  int length = end - start;
   int position = polyglot_as_i32(polyglot_invoke(RUBY_CEXT, "rb_enc_left_char_head",
       rb_tr_unwrap(rb_enc_from_encoding(enc)),
       rb_tr_unwrap(rb_str_new(start, length)),

Original file line number	Diff line number	Diff line change
`@@ -5,6 +5,7 @@ New features:`
`5`	`5`
`6`	`6`	`Bug fixes:`
`7`	`7`
	`8`	+* Fix `rb_enc_left_char_head()` so it is not always `ArgumentError` (#3267, @eregon).
`8`	`9`
`9`	`10`	`Compatibility:`
`10`	`11`