osdep: fix socket_error() to work with Mingw64

Historically QEMU has had a socket_error() macro that was
defined to map to WSASocketError(). The os-win32.h header
file would define errno constants that mapped to the
WSA error constants. This worked fine with Mingw32 since
its header files never defined any errno values, nor did
it even provide an errno.h.  So callers of socket_error()
could match on traditional Exxxx constants and it would
all "just work".

With Mingw64 though, things work rather differently. First
there is an errno.h file which defines all the traditional
errno constants you'd expect from a UNIX platform. There
is then a winerror.h which defined the WSA error constants.
Crucially the WSAExxxx errno values in winerror.h do not
match the Exxxx errno values in error.h.

If QEMU had only imported winerror.h it would still work,
but the qemu/osdep.h file unconditionally imports errno.h.
So callers of socket_error() will get now WSAExxxx values
back and compare them to the Exxx constants. This will
always fail silently at runtime.

To solve this QEMU needs to stop assuming the WSAExxxx
constant values match the Exxx constant values. Thus the
socket_error() macro is turned into a small function that
re-maps WSAExxxx values into Exxx.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index 5b9c4d6143..e9fec2e250 100644
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -34,6 +34,8 @@ void os_daemonize(void);
 void os_setup_post(void);
 int os_mlock(void);
 
+#define socket_error() errno
+
 typedef struct timeval qemu_timeval;
 #define qemu_gettimeofday(tp) gettimeofday(tp, NULL)