[qemu-s390x] [PATCH v3 02/25] chardev: Assert IOCanReadHandler can not be negative

[Philippe Mathieu-Daudé]

The backend should not return a negative length to read.
We will later change the prototype of IOCanReadHandler to return an
unsigned length. Meanwhile make sure the return length is positive.

Suggested-by: Paolo Bonzini <address@hidden>
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
 chardev/char.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/chardev/char.c b/chardev/char.c
index f6d61fa5f8..71ecd32b25 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -159,12 +159,15 @@ int qemu_chr_write(Chardev *s, const uint8_t *buf, int 
len, bool write_all)
 int qemu_chr_be_can_write(Chardev *s)
 {
     CharBackend *be = s->be;
+    int receivable_bytes;
 
     if (!be || !be->chr_can_read) {
         return 0;
     }
 
-    return be->chr_can_read(be->opaque);
+    receivable_bytes = be->chr_can_read(be->opaque);
+    assert(receivable_bytes >= 0);
+    return receivable_bytes;
 }
 
 void qemu_chr_be_write_impl(Chardev *s, uint8_t *buf, int len)
-- 
2.20.1