Prevent an infinite loop parsing a capture name

stevenjohnstone · Earlopain · commit 6e5347803ccb · 2025-12-13T15:17:00.000+01:00
Fixes #3729.
diff --git a/src/prism.c b/src/prism.c
@@ -20395,6 +20395,9 @@ pm_named_capture_escape_unicode(pm_parser_t *parser, pm_buffer_t *unescaped, con
         }
 
         size_t length = pm_strspn_hexadecimal_digit(cursor, end - cursor);
+        if (length == 0) {
+            break;
+        }
         uint32_t value = escape_unicode(parser, cursor, length);
 
         (void) pm_buffer_append_unicode_codepoint(unescaped, value);

Original file line number	Diff line number	Diff line change
`@@ -20395,6 +20395,9 @@ pm_named_capture_escape_unicode(pm_parser_t parser, pm_buffer_t unescaped, con`
`20395`	`20395`	`}`
`20396`	`20396`
`20397`	`20397`	`size_t length = pm_strspn_hexadecimal_digit(cursor, end - cursor);`
	`20398`	`+ if (length == 0) {`
	`20399`	`+ break;`
	`20400`	`+ }`
`20398`	`20401`	`uint32_t value = escape_unicode(parser, cursor, length);`
`20399`	`20402`
`20400`	`20403`	`(void) pm_buffer_append_unicode_codepoint(unescaped, value);`