[Qemu-devel] [PATCH v2 1/2] utils: Add warning messages

[Lluís Vilanova]

Adds a special error object that transforms error messages into
immediately reported warnings.

Signed-off-by: Lluís Vilanova <address@hidden>
---
 include/qapi/error.h |   20 ++++++++++++++++++++
 util/error.c         |   37 +++++++++++++++++++++++++++----------
 2 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/include/qapi/error.h b/include/qapi/error.h
index 4d42cdc..9b7600c 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -57,6 +57,9 @@
  * Call a function treating errors as fatal:
  *     foo(arg, &error_fatal);
  *
+ * Call a function immediately showing all errors as warnings:
+ *     foo(arg, &error_warn);
+ *
  * Receive an error and pass it on to the caller:
  *     Error *err = NULL;
  *     foo(arg, &err);
@@ -108,6 +111,7 @@ ErrorClass error_get_class(const Error *err);
  * then.
  * If @errp is &error_abort, print a suitable message and abort().
  * If @errp is &error_fatal, print a suitable message and exit(1).
+ * If @errp is &error_warn, print a suitable message.
  * If @errp is anything else, address@hidden must be NULL.
  * The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
  * human-readable error message is made from printf-style @fmt, ...
@@ -158,6 +162,7 @@ void error_setg_win32_internal(Error **errp,
  * abort().
  * Else, if @dst_errp is &error_fatal, print a suitable message and
  * exit(1).
+ * Else, if @dst_errp is &error_warn, print a suitable message.
  * Else, if @dst_errp already contains an error, ignore this one: free
  * the error object.
  * Else, move the error object from @local_err to address@hidden
@@ -218,12 +223,27 @@ void error_set_internal(Error **errp,
 
 /*
  * Pass to error_setg() & friends to abort() on error.
+ *
+ * WARNING: Do _not_ use for errors that are (or can be) triggered by guest 
code
+ *          (e.g., some unimplimented corner case in guest code translation or
+ *          device code). Otherwise that can be abused by guest code to
+ *          terminate QEMU.
  */
 extern Error *error_abort;
 
 /*
  * Pass to error_setg() & friends to exit(1) on error.
+ *
+ * WARNING: Do _not_ use for errors that are (or can be) triggered by guest 
code
+ *          (e.g., some unimplimented corner case in guest code translation or
+ *          device code). Otherwise that can be abused by guest code to
+ *          terminate QEMU.
  */
 extern Error *error_fatal;
 
+/*
+ * Pass to error_setg() & friends to immediately show an error as a warning.
+ */
+extern Error *error_warn;
+
 #endif
diff --git a/util/error.c b/util/error.c
index 80c89a2..85170e54 100644
--- a/util/error.c
+++ b/util/error.c
@@ -15,6 +15,7 @@
 #include "qemu-common.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
+#include "qemu/timer.h"
 
 struct Error
 {
@@ -27,8 +28,9 @@ struct Error
 
 Error *error_abort;
 Error *error_fatal;
+Error *error_warn;
 
-static void error_handle_fatal(Error **errp, Error *err)
+static bool error_handle_fatal(Error **errp, Error *err)
 {
     if (errp == &error_abort) {
         fprintf(stderr, "Unexpected error in %s() at %s:%d:\n",
@@ -40,6 +42,20 @@ static void error_handle_fatal(Error **errp, Error *err)
         error_report_err(err);
         exit(1);
     }
+
+    if (errp == &error_warn) {
+        /* cannot use error_report_err() because it adds newlines */
+        error_report("warning: [%s() at %s:%d] %s",
+                     err->func, err->src, err->line, err->msg);
+        if (err->hint) {
+            error_printf_unless_qmp("warning: [%s() at %s:%d] %s",
+                                    err->func, err->src, err->line,
+                                    err->hint->str);
+        }
+        return true;
+    } else {
+        return false;
+    }
 }
 
 static void error_setv(Error **errp,
@@ -61,10 +77,10 @@ static void error_setv(Error **errp,
     err->line = line;
     err->func = func;
 
-    error_handle_fatal(errp, err);
-    *errp = err;
-
-    errno = saved_errno;
+    if (!error_handle_fatal(errp, err)) {
+        *errp = err;
+        errno = saved_errno;
+    }
 }
 
 void error_set_internal(Error **errp,
@@ -232,10 +248,11 @@ void error_propagate(Error **dst_errp, Error *local_err)
     if (!local_err) {
         return;
     }
-    error_handle_fatal(dst_errp, local_err);
-    if (dst_errp && !*dst_errp) {
-        *dst_errp = local_err;
-    } else {
-        error_free(local_err);
+    if (!error_handle_fatal(dst_errp, local_err)) {
+        if (dst_errp && !*dst_errp) {
+            *dst_errp = local_err;
+        } else {
+            error_free(local_err);
+        }
     }
 }