[Qemu-devel] [PATCH v2 1/3] error: don't rely on pointer comparisons

["Michael S. Tsirkin" <mst@redhat.com>]

makes it possible to copy error_abort pointers,
not just pass them on directly.

This is needed because follow-up patches add support for
    Error *local_err = ...;
as a way to set an abort-on-error pointer, which requires that we have
more than just a global error_abort abort-on-error pointer, but that any
number of pointers all resolve to something specific.

Add an assert statement when class is retrieved, to make sure we still
get a core-dump if we (somehow) attempt to output the abort errp by
mistake.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 util/error.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/util/error.c b/util/error.c
index 14f4351..e10cb34 100644
--- a/util/error.c
+++ b/util/error.c
@@ -20,7 +20,13 @@ struct Error
     ErrorClass err_class;
 };
 
-Error *error_abort;
+static Error error_abort_st = { .err_class = ERROR_CLASS_MAX };
+Error *error_abort = &error_abort_st;
+
+static bool error_is_abort(Error **errp)
+{
+    return errp && *errp == error_abort;
+}
 
 void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
 {
@@ -40,7 +46,7 @@ void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
     va_end(ap);
     err->err_class = err_class;
 
-    if (errp == &error_abort) {
+    if (error_is_abort(errp)) {
         error_report_err(err);
         abort();
     }
@@ -76,7 +82,7 @@ void error_set_errno(Error **errp, int os_errno, ErrorClass err_class,
     va_end(ap);
     err->err_class = err_class;
 
-    if (errp == &error_abort) {
+    if (error_is_abort(errp)) {
         error_report_err(err);
         abort();
     }
@@ -121,7 +127,7 @@ void error_set_win32(Error **errp, int win32_err, ErrorClass err_class,
     va_end(ap);
     err->err_class = err_class;
 
-    if (errp == &error_abort) {
+    if (error_is_abort(errp)) {
         error_report_err(err);
         abort();
     }
@@ -144,6 +150,7 @@ Error *error_copy(const Error *err)
 
 ErrorClass error_get_class(const Error *err)
 {
+    assert(err->err_class < ERROR_CLASS_MAX);
     return err->err_class;
 }
 
@@ -168,7 +175,7 @@ void error_free(Error *err)
 
 void error_propagate(Error **dst_errp, Error *local_err)
 {
-    if (local_err && dst_errp == &error_abort) {
+    if (local_err && error_is_abort(dst_errp)) {
         error_report_err(local_err);
         abort();
     } else if (dst_errp && !*dst_errp) {
-- 
MST