Fix #78976: SplFileObject::fputcsv returns -1 on failure

`php_stream_write()` returns `-1` on failure now, which has to be
catered to by `SplFileObject::fputcsv()` which still is supposed to
return `false` on failure.

Author: cmb69

NEWS

@@ -15,6 +15,9 @@ PHP                                                                        NEWS
   . Fixed bug #78903 (Conflict in RTD key for closures results in crash).
     (Nikita)
 
+- Spl:
+  . Fixed bug #78976 (SplFileObject::fputcsv returns -1 on failure). (cmb)
+
 19 Dec 2019, PHP 7.4.1
 
 - Core:

ext/spl/spl_directory.c

@@ -2668,6 +2668,9 @@ SPL_METHOD(SplFileObject, fputcsv)
 			break;
 		}
 		ret = php_fputcsv(intern->u.file.stream, fields, delimiter, enclosure, escape);
+		if (ret < 0) {
+			RETURN_FALSE;
+		}
 		RETURN_LONG(ret);
 	}
 }

ext/spl/tests/bug78976.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Bug #78976 (SplFileObject::fputcsv returns -1 on failure)
+--FILE--
+<?php
+$file = new SplFileObject('php://memory', 'r');
+var_dump($file->fputcsv(['foo', 'bar']));
+?>
+--EXPECT--
+bool(false)