Fix output buffer discard on memory limit

Move this code directly into the error handler, and check the
heap->overflow flag. Discarding output here allows us to print
the normal memory limit message to standard output. Otherwise
nothing would be printed unless a different log medium was used,
which makes for a suboptimal debugging experience.

Author: nikic

Zend/zend_alloc.c

@@ -2669,6 +2669,15 @@ ZEND_API zend_result zend_set_memory_limit(size_t memory_limit)
 	return SUCCESS;
 }
 
+ZEND_API bool zend_alloc_in_memory_limit_error_reporting(void)
+{
+#if ZEND_MM_LIMIT
+	return AG(mm_heap)->overflow;
+#else
+	return false;
+#endif
+}
+
 ZEND_API size_t zend_memory_usage(bool real_usage)
 {
 #if ZEND_MM_STAT

Zend/zend_alloc.h

@@ -220,6 +220,7 @@ ZEND_API void * __zend_realloc(void *p, size_t len) ZEND_ATTRIBUTE_ALLOC_SIZE(2)
 #define pestrdup_rel(s, persistent) ((persistent)?strdup(s):estrdup_rel(s))
 
 ZEND_API zend_result zend_set_memory_limit(size_t memory_limit);
+ZEND_API bool zend_alloc_in_memory_limit_error_reporting(void);
 
 ZEND_API void start_memory_manager(void);
 ZEND_API void shutdown_memory_manager(bool silent, bool full_shutdown);

main/main.c

@@ -1235,6 +1235,10 @@ static ZEND_COLD void php_error_cb(int orig_type, zend_string *error_filename, c
 		PG(last_error_lineno) = error_lineno;
 	}
 
+	if (zend_alloc_in_memory_limit_error_reporting()) {
+		php_output_discard_all();
+	}
+
 	/* display/log the error if necessary */
 	if (display && ((EG(error_reporting) & type) || (type & E_CORE))
 		&& (PG(log_errors) || PG(display_errors) || (!module_initialized))) {
@@ -1783,19 +1787,7 @@ void php_request_shutdown(void *dummy)
 
 	/* 3. Flush all output buffers */
 	zend_try {
-		bool send_buffer = SG(request_info).headers_only ? 0 : 1;
-
-		if (CG(unclean_shutdown) && PG(last_error_type) == E_ERROR &&
-			(size_t)PG(memory_limit) < zend_memory_usage(1)
-		) {
-			send_buffer = 0;
-		}
-
-		if (!send_buffer) {
-			php_output_discard_all();
-		} else {
-			php_output_end_all();
-		}
+		php_output_end_all();
 	} zend_end_try();
 
 	/* 4. Reset max_execution_time (no longer executing php code after response sent) */

tests/lang/bug45392.phpt

@@ -1,9 +1,5 @@
 --TEST--
 Bug #45392 (ob_start()/ob_end_clean() and memory_limit)
---INI--
-display_errors=stderr
---XFAIL--
-The issue has not yet been resolved.
 --SKIPIF--
 <?php
 if (getenv("USE_ZEND_ALLOC") === "0") {
@@ -22,4 +18,5 @@ ob_end_clean();
 ?>
 --EXPECTF--
 2
+
 Fatal error: Allowed memory size of %d bytes exhausted%s