Fix GH-19942: avoid infinite loop when using iterator_count() on an empty SplFileObject

NEWS

@@ -27,6 +27,10 @@ PHP                                                                        NEWS
     of the curl_copy_handle() function to clone a CurlHandle. (timwolla)
   . Fix curl build failure on macOS+curl 8.16. (nielsdos)
 
+- SPL:
+  . Fixed bug GH-19942 (iterator_count() on an empty SplFileObject looping
+    infinitely). (alexandre-daubois)
+
 - Soap:
   . Fixed bug GH-19784 (SoapServer memory leak). (nielsdos)
 

ext/spl/spl_directory.c

@@ -2166,6 +2166,29 @@ PHP_METHOD(SplFileObject, valid)
 	if (!intern->u.file.stream) {
 		RETURN_FALSE;
 	}
+
+	/* For empty files, php_stream_eof() might not return TRUE until after a read attempt.
+	 * If we're at the beginning and haven't read anything, check EOF directly after ensuring
+	 * a read has been attempted (only on seekable streams). */
+	if (!intern->u.file.current_line && Z_ISUNDEF(intern->u.file.current_zval) &&
+		intern->u.file.current_line_num == 0) {
+
+		if (intern->u.file.stream->ops->seek &&
+			(intern->u.file.stream->flags & PHP_STREAM_FLAG_NO_SEEK) == 0) {
+
+			if (php_stream_eof(intern->u.file.stream)) {
+				RETURN_FALSE;
+			}
+
+			if (php_stream_tell(intern->u.file.stream) == 0) {
+				php_stream_statbuf ssb;
+				if (php_stream_stat(intern->u.file.stream, &ssb) == 0 && ssb.sb.st_size == 0) {
+					RETURN_FALSE;
+				}
+			}
+		}
+	}
+
 	RETURN_BOOL(!php_stream_eof(intern->u.file.stream));
 } /* }}} */
 

ext/spl/tests/SplFileObject_iterator_count_empty_file.phpt

@@ -0,0 +1,16 @@
+--TEST--
+GH-19942 (iterator_count() on an empty SplFileObject should return 0)
+--FILE--
+<?php
+$tmpfile = tempnam(sys_get_temp_dir(), 'spl_empty_test');
+touch($tmpfile);
+
+$fileObject = new SplFileObject($tmpfile, 'r');
+$count = iterator_count($fileObject);
+
+var_dump($count);
+
+unlink($tmpfile);
+?>
+--EXPECT--
+int(0)

ext/spl/tests/SplFileObject_non_seekable_stream.phpt

@@ -0,0 +1,11 @@
+--TEST--
+SplFileObject::valid() with non-seekable streams should not hang
+--FILE--
+<?php
+$file = new SplFileObject("php://stdin", "r");
+var_dump($file->valid());
+?>
+--STDIN--
+
+--EXPECT--
+bool(true)