tests: send error_report to test log

Implement error_vprintf to send the output of error_report to
the test log.  This silences test-vmstate.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1477326663-67817-3-git-send-email-pbonzini@redhat.com>

include/glib-compat.h

@@ -315,4 +315,17 @@ static inline void g_source_set_name_by_id(guint tag, const char *name)
 }
 #endif
 
+#if !GLIB_CHECK_VERSION(2, 36, 0)
+/* Always fail.  This will not include error_report output in the test log,
+ * sending it instead to stderr.
+ */
+#define g_test_initialized() (0)
+#endif
+#if !GLIB_CHECK_VERSION(2, 38, 0)
+#ifdef CONFIG_HAS_GLIB_SUBPROCESS_TESTS
+#error schizophrenic detection of glib subprocess testing
+#endif
+#define g_test_subprocess() (0)
+#endif
+
 #endif

stubs/error-printf.c

@@ -4,7 +4,13 @@
 
 void error_vprintf(const char *fmt, va_list ap)
 {
-    vfprintf(stderr, fmt, ap);
+    if (g_test_initialized() && !g_test_subprocess()) {
+        char *msg = g_strdup_vprintf(fmt, ap);
+        g_test_message("%s", msg);
+        g_free(msg);
+    } else {
+        vfprintf(stderr, fmt, ap);
+    }
 }
 
 void error_vprintf_unless_qmp(const char *fmt, va_list ap)