Re: [PATCH v2 7/9] chardev/char: Preserve %errno in qemu_chr_write()

[Philippe Mathieu-Daudé]

On 22/10/25 17:07, Philippe Mathieu-Daudé wrote:

qemu_chr_write() dispatches to ChardevClass::chr_write(),
and is expected to propagate the backend error, not some
unrelated one produce by "best effort" logfile or replay.
Preserve and return the relevant %errno.

Cc: qemu-sta...@nongnu.org

Suggested-by: Peter Maydell <peter.mayd...@linaro.org>

Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>
---
  chardev/char.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/chardev/char.c b/chardev/char.c
index 5c8130b2435..2af402d9855 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -113,6 +113,7 @@ static int qemu_chr_write_buffer(Chardev *s,
                                   int *offset, bool write_all)
  {
      ChardevClass *cc = CHARDEV_GET_CLASS(s);
+    int saved_errno;
      int res = 0;
      *offset = 0;

@@ -138,6 +139,7 @@ static int qemu_chr_write_buffer(Chardev *s,

              break;
          }
      }
+    saved_errno = errno;
      if (*offset > 0) {
          /*
           * If some data was written by backend, we should
@@ -154,6 +156,7 @@ static int qemu_chr_write_buffer(Chardev *s,
           */
          qemu_chr_write_log(s, buf, len);
      }
+    errno = saved_errno;
      qemu_mutex_unlock(&s->chr_write_lock);

return res;

@@ -186,7 +189,9 @@ int qemu_chr_write(Chardev *s, const uint8_t *buf, int len, 
bool write_all)
      res = qemu_chr_write_buffer(s, buf, len, &offset, write_all);

if (qemu_chr_replay(s) && replay_mode == REPLAY_MODE_RECORD) {

+        int saved_errno = errno;
          replay_char_write_event_save(res, offset);
+        errno = saved_errno;
      }

if (res < 0 && offset == 0) {