[PATCH v7 03/11] scripts: add coccinelle script to use auto propagated errp

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Script adds ERRP_AUTO_PROPAGATE macro invocation where appropriate and
does corresponding changes in code (look for details in
include/qapi/error.h)

Usage example:
spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
 --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff \
 blockdev-nbd.c qemu-nbd.c {block/nbd*,nbd/*,include/block/nbd*}.[hc]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---

CC: Eric Blake <eblake@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Greg Kurz <groug@kaod.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Anthony Perard <anthony.perard@citrix.com>
CC: Paul Durrant <paul@xen.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: "Philippe Mathieu-Daudé" <philmd@redhat.com>
CC: Laszlo Ersek <lersek@redhat.com>
CC: Gerd Hoffmann <kraxel@redhat.com>
CC: Stefan Berger <stefanb@linux.ibm.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
CC: qemu-block@nongnu.org
CC: xen-devel@lists.xenproject.org

 include/qapi/error.h                          |   3 +
 scripts/coccinelle/auto-propagated-errp.cocci | 158 ++++++++++++++++++
 2 files changed, 161 insertions(+)
 create mode 100644 scripts/coccinelle/auto-propagated-errp.cocci

diff --git a/include/qapi/error.h b/include/qapi/error.h
index b9452d4806..79f8e95214 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -141,6 +141,9 @@
  *         ...
  *     }
  *
+ * For mass conversion use script
+ *   scripts/coccinelle/auto-propagated-errp.cocci
+ *
  *
  * Receive and accumulate multiple errors (first one wins):
  *     Error *err = NULL, *local_err = NULL;
diff --git a/scripts/coccinelle/auto-propagated-errp.cocci b/scripts/coccinelle/auto-propagated-errp.cocci
new file mode 100644
index 0000000000..fb03c871cb
--- /dev/null
+++ b/scripts/coccinelle/auto-propagated-errp.cocci
@@ -0,0 +1,158 @@
+// Use ERRP_AUTO_PROPAGATE (see include/qapi/error.h)
+//
+// Copyright (c) 2020 Virtuozzo International GmbH.
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// Usage example:
+// spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
+//  --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff \
+//  blockdev-nbd.c qemu-nbd.c {block/nbd*,nbd/*,include/block/nbd*}.[hc]
+
+@rule0@
+// Add invocation to errp-functions where necessary
+// We should skip functions with "Error *const *errp"
+// parameter, but how to do it with coccinelle?
+// I don't know, so, I skip them by function name regex.
+// It's safe: if we did not skip some functions with
+// "Error *const *errp", ERRP_AUTO_PROPAGATE invocation
+// will fail to compile, because of const violation.
+identifier fn !~ "error_append_.*_hint";
+identifier local_err, ERRP;
+@@
+
+ fn(..., Error **ERRP, ...)
+ {
++   ERRP_AUTO_PROPAGATE();
+    <+...
+        when != ERRP_AUTO_PROPAGATE();
+(
+    error_append_hint(ERRP, ...);
+|
+    error_prepend(ERRP, ...);
+|
+    Error *local_err = NULL;
+)
+    ...+>
+ }
+
+@@
+// Switch unusual (Error **) parameter names to errp
+// (this is necessary to use ERRP_AUTO_PROPAGATE).
+identifier rule0.fn;
+identifier rule0.ERRP != errp;
+@@
+
+ fn(...,
+-   Error **ERRP
++   Error **errp
+    ,...)
+ {
+     <...
+-    ERRP
++    errp
+     ...>
+ }
+
+@rule1@
+// We want to patch error propagation in functions regardless of
+// whether the function already uses ERRP_AUTO_PROPAGATE prior to
+// applying rule0, hence this one does not inherit from it.
+identifier fn !~ "error_append_.*_hint";
+identifier local_err;
+symbol errp;
+@@
+
+ fn(..., Error **errp, ...)
+ {
+     <...
+-    Error *local_err = NULL;
+     ...>
+ }
+
+@@
+// Handle pattern with goto, otherwise we'll finish up
+// with labels at function end which will not compile.
+identifier rule1.fn, rule1.local_err;
+identifier OUT;
+@@
+
+ fn(...)
+ {
+     <...
+-    goto OUT;
++    return;
+     ...>
+- OUT:
+-    error_propagate(errp, local_err);
+ }
+
+@@
+identifier rule1.fn, rule1.local_err;
+expression list args; // to reindent error_propagate_prepend
+@@
+
+ fn(...)
+ {
+     <...
+(
+-    error_free(local_err);
+-    local_err = NULL;
++    error_free_errp(errp);
+|
+-    error_free(local_err);
++    error_free_errp(errp);
+|
+-    error_report_err(local_err);
++    error_report_errp(errp);
+|
+-    warn_report_err(local_err);
++    warn_report_errp(errp);
+|
+-    error_propagate_prepend(errp, local_err, args);
++    error_prepend(errp, args);
+|
+-    error_propagate(errp, local_err);
+)
+     ...>
+ }
+
+@@
+identifier rule1.fn, rule1.local_err;
+@@
+
+ fn(...)
+ {
+     <...
+(
+-    &local_err
++    errp
+|
+-    local_err
++    *errp
+)
+     ...>
+ }
+
+@@
+identifier rule1.fn;
+@@
+
+ fn(...)
+ {
+     <...
+- *errp != NULL
++ *errp
+     ...>
+ }
-- 
2.21.0