compiler: support Darwin weak references

Weakrefs only tell you if the symbol was defined elsewhere, so you
need a further check at runtime to pick the default definition
when needed.

This could be automated by the compiler, but it does not do it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

compiler.h

@@ -50,8 +50,15 @@
 #   define __printf__ __gnu_printf__
 #  endif
 # endif
-# define QEMU_WEAK_ALIAS(newname, oldname) \
+# if defined(__APPLE__)
+#  define QEMU_WEAK_ALIAS(newname, oldname) \
+        static typeof(oldname) weak_##newname __attribute__((unused, weakref(#oldname)))
+#  define QEMU_WEAK_REF(newname, oldname) (weak_##newname ? weak_##newname : oldname)
+# else
+#  define QEMU_WEAK_ALIAS(newname, oldname) \
         typeof(oldname) newname __attribute__((weak, alias (#oldname)))
+#  define QEMU_WEAK_REF(newname, oldname) newname
+# endif
 #else
 #define GCC_ATTR /**/
 #define GCC_FMT_ATTR(n, m)

osdep.c

@@ -54,6 +54,38 @@ static bool fips_enabled = false;
 
 static const char *qemu_version = QEMU_VERSION;
 
+static int default_fdset_get_fd(int64_t fdset_id, int flags)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_get_fd, default_fdset_get_fd);
+#define monitor_fdset_get_fd \
+    QEMU_WEAK_REF(monitor_fdset_get_fd, default_fdset_get_fd)
+
+static int default_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_add, default_fdset_dup_fd_add);
+#define monitor_fdset_dup_fd_add \
+    QEMU_WEAK_REF(monitor_fdset_dup_fd_add, default_fdset_dup_fd_add)
+
+static int default_fdset_dup_fd_remove(int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_remove, default_fdset_dup_fd_remove);
+#define monitor_fdset_dup_fd_remove \
+    QEMU_WEAK_REF(monitor_fdset_dup_fd_remove, default_fdset_dup_fd_remove)
+
+static int default_fdset_dup_fd_find(int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_find, default_fdset_dup_fd_find);
+#define monitor_fdset_dup_fd_find \
+    QEMU_WEAK_REF(monitor_fdset_dup_fd_remove, default_fdset_dup_fd_find)
+
 int socket_set_cork(int fd, int v)
 {
 #if defined(SOL_TCP) && defined(TCP_CORK)
@@ -400,27 +432,3 @@ bool fips_get_state(void)
     return fips_enabled;
 }
 
-
-static int default_fdset_get_fd(int64_t fdset_id, int flags)
-{
-    return -1;
-}
-QEMU_WEAK_ALIAS(monitor_fdset_get_fd, default_fdset_get_fd);
-
-static int default_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
-{
-    return -1;
-}
-QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_add, default_fdset_dup_fd_add);
-
-static int default_fdset_dup_fd_remove(int dup_fd)
-{
-    return -1;
-}
-QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_remove, default_fdset_dup_fd_remove);
-
-static int default_fdset_dup_fd_find(int dup_fd)
-{
-    return -1;
-}
-QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_find, default_fdset_dup_fd_find);

oslib-win32.c

@@ -32,6 +32,13 @@
 #include "trace.h"
 #include "qemu_socket.h"
 
+static void default_qemu_fd_register(int fd)
+{
+}
+QEMU_WEAK_ALIAS(qemu_fd_register, default_qemu_fd_register);
+#define qemu_fd_register \
+    QEMU_WEAK_REF(qemu_fd_register, default_qemu_fd_register)
+
 void *qemu_oom_check(void *ptr)
 {
     if (ptr == NULL) {
@@ -150,8 +157,3 @@ int qemu_get_thread_id(void)
 {
     return GetCurrentThreadId();
 }
-
-static void default_qemu_fd_register(int fd)
-{
-}
-QEMU_WEAK_ALIAS(qemu_fd_register, default_qemu_fd_register);

qemu-sockets.c

@@ -61,6 +61,28 @@ static QemuOptsList dummy_opts = {
     },
 };
 
+static int default_monitor_get_fd(Monitor *mon, const char *name, Error **errp)
+{
+    error_setg(errp, "only QEMU supports file descriptor passing");
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_get_fd, default_monitor_get_fd);
+#define monitor_get_fd \
+    QEMU_WEAK_REF(monitor_get_fd, default_monitor_get_fd)
+
+static int default_qemu_set_fd_handler2(int fd,
+                                        IOCanReadHandler *fd_read_poll,
+                                        IOHandler *fd_read,
+                                        IOHandler *fd_write,
+                                        void *opaque)
+
+{
+    abort();
+}
+QEMU_WEAK_ALIAS(qemu_set_fd_handler2, default_qemu_set_fd_handler2);
+#define qemu_set_fd_handler2 \
+    QEMU_WEAK_REF(qemu_set_fd_handler2, default_qemu_set_fd_handler2)
+
 static int inet_getport(struct addrinfo *e)
 {
     struct sockaddr_in *i4;
@@ -967,21 +989,3 @@ int socket_init(void)
 #endif
     return 0;
 }
-
-static int default_monitor_get_fd(Monitor *mon, const char *name, Error **errp)
-{
-    error_setg(errp, "only QEMU supports file descriptor passing");
-    return -1;
-}
-QEMU_WEAK_ALIAS(monitor_get_fd, default_monitor_get_fd);
-
-static int default_qemu_set_fd_handler2(int fd,
-                                        IOCanReadHandler *fd_read_poll,
-                                        IOHandler *fd_read,
-                                        IOHandler *fd_write,
-                                        void *opaque)
-
-{
-    abort();
-}
-QEMU_WEAK_ALIAS(qemu_set_fd_handler2, default_qemu_set_fd_handler2);

qmp.c

@@ -477,6 +477,8 @@ static CpuDefinitionInfoList *default_arch_query_cpu_definitions(Error **errp)
     return NULL;
 }
 QEMU_WEAK_ALIAS(arch_query_cpu_definitions, default_arch_query_cpu_definitions);
+#define arch_query_cpu_definitions \
+    QEMU_WEAK_REF(arch_query_cpu_definitions, default_arch_query_cpu_definitions)
 
 CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
 {