error: add global &error_warn destination

This can help debugging issues or develop, when error handling is
introduced.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Message-Id: <20230221124802.4103554-6-marcandre.lureau@redhat.com>

include/qapi/error.h

@@ -519,6 +519,12 @@ static inline void error_propagator_cleanup(ErrorPropagator *prop)
 
 G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup);
 
+/*
+ * Special error destination to warn on error.
+ * See error_setg() and error_propagate() for details.
+ */
+extern Error *error_warn;
+
 /*
  * Special error destination to abort on error.
  * See error_setg() and error_propagate() for details.

tests/unit/test-error-report.c

@@ -12,6 +12,7 @@
 #include <locale.h>
 
 #include "qemu/error-report.h"
+#include "qapi/error.h"
 
 static void
 test_error_report_simple(void)
@@ -103,6 +104,22 @@ test_error_report_timestamp(void)
 ");
 }
 
+static void
+test_error_warn(void)
+{
+    if (g_test_subprocess()) {
+        error_setg(&error_warn, "Testing &error_warn");
+        return;
+    }
+
+    g_test_trap_subprocess(NULL, 0, 0);
+    g_test_trap_assert_passed();
+    g_test_trap_assert_stderr("\
+test-error-report: warning: Testing &error_warn*\
+");
+}
+
+
 int
 main(int argc, char *argv[])
 {
@@ -116,6 +133,7 @@ main(int argc, char *argv[])
     g_test_add_func("/error-report/glog", test_error_report_glog);
     g_test_add_func("/error-report/once", test_error_report_once);
     g_test_add_func("/error-report/timestamp", test_error_report_timestamp);
+    g_test_add_func("/error-report/warn", test_error_warn);
 
     return g_test_run();
 }

util/error.c

@@ -27,8 +27,9 @@ struct Error
 
 Error *error_abort;
 Error *error_fatal;
+Error *error_warn;
 
-static void error_handle_fatal(Error **errp, Error *err)
+static void error_handle(Error **errp, Error *err)
 {
     if (errp == &error_abort) {
         fprintf(stderr, "Unexpected error in %s() at %s:%d:\n",
@@ -43,6 +44,9 @@ static void error_handle_fatal(Error **errp, Error *err)
         error_report_err(err);
         exit(1);
     }
+    if (errp == &error_warn) {
+        warn_report_err(err);
+    }
 }
 
 G_GNUC_PRINTF(6, 0)
@@ -71,7 +75,7 @@ static void error_setv(Error **errp,
     err->line = line;
     err->func = func;
 
-    error_handle_fatal(errp, err);
+    error_handle(errp, err);
     *errp = err;
 
     errno = saved_errno;
@@ -284,7 +288,7 @@ void error_propagate(Error **dst_errp, Error *local_err)
     if (!local_err) {
         return;
     }
-    error_handle_fatal(dst_errp, local_err);
+    error_handle(dst_errp, local_err);
     if (dst_errp && !*dst_errp) {
         *dst_errp = local_err;
     } else {