Reduce size limit in parser fuzzer

Avoid stack overflows during compilation of deeply nested
expressions.

Author: nikic

sapi/fuzzer/fuzzer-parser.c

@@ -27,7 +27,7 @@
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
 	char *s;
-	if (Size > 64 * 1024) {
+	if (Size > 32 * 1024) {
 		/* Large inputs have a large impact on fuzzer performance,
 		 * but are unlikely to be necessary to reach new codepaths. */
 		return 0;

sapi/fuzzer/generate_parser_corpus.php

@@ -9,11 +9,13 @@
 $corpusDir = __DIR__ . '/corpus/parser';
 @mkdir($corpusDir);
 
+$maxLen = 32 * 1024;
 foreach ($it as $file) {
     if (!preg_match('/\.phpt$/', $file)) continue;
     $code = file_get_contents($file);
     if (!preg_match('/--FILE--\R(.*?)\R--([_A-Z]+)--/s', $code, $matches)) continue;
     $code = $matches[1];
+    if (strlen($code) > $maxLen) continue;
 
     $outFile = str_replace($testsDir, '', $file);
     $outFile = str_replace('/', '_', $outFile);