qemu-print: New qemu_printf(), qemu_vprintf() etc.

We commonly want to print to the current monitor if we have one, else
to stdout/stderr.  For stderr, have error_printf().  For stdout, all
we have is monitor_vfprintf(), which is rather unwieldy.  We often
print to stderr just because error_printf() is easier.

New qemu_printf() and qemu_vprintf() do exactly what's needed.  The
next commits will put them to use.

Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190417190641.26814-12-armbru@redhat.com>

MAINTAINERS

@@ -1895,6 +1895,8 @@ F: hmp.[ch]
 F: hmp-commands*.hx
 F: include/monitor/hmp-target.h
 F: tests/test-hmp.c
+F: include/qemu/qemu-print.h
+F: util/qemu-print.c
 
 Network device backends
 M: Jason Wang <jasowang@redhat.com>

include/qemu/qemu-print.h

@@ -0,0 +1,19 @@
+/*
+ * Print to stream or current monitor
+ *
+ * Copyright (C) 2019 Red Hat Inc.
+ *
+ * Authors:
+ *  Markus Armbruster <armbru@redhat.com>,
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef QEMU_PRINT_H
+#define QEMU_PRINT_H
+
+int qemu_vprintf(const char *fmt, va_list ap) GCC_FMT_ATTR(1, 0);
+int qemu_printf(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
+
+#endif

stubs/monitor.c

@@ -6,6 +6,11 @@
 
 __thread Monitor *cur_mon;
 
+int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
+{
+    abort();
+}
+
 int monitor_get_fd(Monitor *mon, const char *name, Error **errp)
 {
     error_setg(errp, "only QEMU supports file descriptor passing");

tests/test-util-sockets.c

@@ -70,6 +70,7 @@ int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
  * otherwise we get duplicate syms at link time.
  */
 __thread Monitor *cur_mon;
+int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap) { abort(); }
 void monitor_init(Chardev *chr, int flags) {}
 
 

util/Makefile.objs

@@ -23,6 +23,7 @@ util-obj-y += bitmap.o bitops.o hbitmap.o
 util-obj-y += fifo8.o
 util-obj-y += cacheinfo.o
 util-obj-y += error.o qemu-error.o
+util-obj-y += qemu-print.o
 util-obj-y += id.o
 util-obj-y += iov.o qemu-config.o qemu-sockets.o uri.o notify.o
 util-obj-y += qemu-option.o qemu-progress.o

util/qemu-print.c

@@ -0,0 +1,42 @@
+/*
+ * Print to stream or current monitor
+ *
+ * Copyright (C) 2019 Red Hat Inc.
+ *
+ * Authors:
+ *  Markus Armbruster <armbru@redhat.com>,
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "monitor/monitor.h"
+#include "qemu/qemu-print.h"
+
+/*
+ * Print like vprintf().
+ * Print to current monitor if we have one, else to stdout.
+ */
+int qemu_vprintf(const char *fmt, va_list ap)
+{
+    if (cur_mon) {
+        return monitor_vprintf(cur_mon, fmt, ap);
+    }
+    return vprintf(fmt, ap);
+}
+
+/*
+ * Print like printf().
+ * Print to current monitor if we have one, else to stdout.
+ */
+int qemu_printf(const char *fmt, ...)
+{
+    va_list ap;
+    int ret;
+
+    va_start(ap, fmt);
+    ret = qemu_vprintf(fmt, ap);
+    va_end(ap);
+    return ret;
+}