In some places in we put an error into a local Error*, but forget
to check for failure and pass it back to the caller.
Add a Coccinelle patch to catch and automatically add the missing
code.

Inspired-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
v3: Fixed typo 'provides', let prototype return 'void' (eblake)
---
 .../add-missing-error_propagate.cocci         | 30 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 31 insertions(+)
 create mode 100644 scripts/coccinelle/add-missing-error_propagate.cocci

diff --git a/scripts/coccinelle/add-missing-error_propagate.cocci b/scripts/coccinelle/add-missing-error_propagate.cocci
new file mode 100644
index 0000000000..4b82e40418
--- /dev/null
+++ b/scripts/coccinelle/add-missing-error_propagate.cocci
@@ -0,0 +1,30 @@
+// Add missing error-propagation code where caller provides a Error* argument
+//
+// Copyright: (C) 2020 Philippe Mathieu-Daudé
+// This work is licensed under the terms of the GNU GPLv2 or later.
+//
+// spatch \
+//  --macro-file scripts/cocci-macro-file.h --include-headers \
+//  --sp-file scripts/coccinelle/add-missing-error_propagate.cocci \
+//  --keep-comments --in-place
+//
+// Inspired by https://www.mail-archive.com/qemu-devel@nongnu.org/msg691638.html
+
+
+@ add_missing_error_propagate @
+typedef Error;
+Error *local_err;
+identifier func, errp, errfunc1, errfunc2;
+@@
+void func(..., Error **errp)
+{
+    <...
+    errfunc1(..., &local_err);
++   if (local_err) {
++       error_propagate(errp, local_err);
++       return;
++   }
+    ... when != local_err
+    errfunc2(..., &local_err);
+    ...>
+}
diff --git a/MAINTAINERS b/MAINTAINERS
index 54e05ecbdf..f996e72780 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2054,6 +2054,7 @@ F: include/qemu/error-report.h
 F: qapi/error.json
 F: util/error.c
 F: util/qemu-error.c
+F: scripts/coccinelle/add-missing-error_propagate.cocci
 F: scripts/coccinelle/err-bad-newline.cocci
 F: scripts/coccinelle/error-use-after-free.cocci
 F: scripts/coccinelle/error_propagate_null.cocci
-- 
2.21.1