From d64336e1a98d47f3484e69b7eaf19f105379c171 Mon Sep 17 00:00:00 2001
From: Gary Li <gary.li1@uwaterloo.ca>
Date: Wed, 26 Jun 2024 14:18:41 -0400
Subject: [PATCH] g_output_stream_write: Allow NULL buffer if count is 0

We currently fail a buffer != NULL assertion if buffer is NULL and count is 0. Allow this case without critical assertions.

Fixes https://gitlab.gnome.org/GNOME/glib/-/issues/3402
---
 gio/goutputstream.c              | 2 +-
 gio/tests/memory-output-stream.c | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/gio/goutputstream.c b/gio/goutputstream.c
index 1348208dd..dfecfb2fc 100644
--- a/gio/goutputstream.c
+++ b/gio/goutputstream.c
@@ -216,7 +216,7 @@ g_output_stream_write (GOutputStream  *stream,
   gssize res;
 
   g_return_val_if_fail (G_IS_OUTPUT_STREAM (stream), -1);
-  g_return_val_if_fail (buffer != NULL, 0);
+  g_return_val_if_fail (buffer != NULL || count == 0, 0);
 
   if (count == 0)
     return 0;
diff --git a/gio/tests/memory-output-stream.c b/gio/tests/memory-output-stream.c
index a517cb964..60733511f 100644
--- a/gio/tests/memory-output-stream.c
+++ b/gio/tests/memory-output-stream.c
@@ -307,6 +307,7 @@ test_write_null (void)
 {
   GOutputStream *mo;
   GError *error = NULL;
+  gssize bytes_written;
 
   g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2471");
 
@@ -316,6 +317,10 @@ test_write_null (void)
 
   g_assert_cmpint (0, ==, g_memory_output_stream_get_data_size (G_MEMORY_OUTPUT_STREAM (mo)));
 
+  bytes_written = g_output_stream_write (mo, NULL, 0, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_cmpint (0, ==, bytes_written);
+
   g_output_stream_close (mo, NULL, &error);
   g_assert_no_error (error);
   g_object_unref (mo);