[PATCH-for-5.1 v3 3/7] scripts/coccinelle: Find eventually missing error_propagate() calls

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

In some places in we put an error into a local Error*, but
forget to use it. Add a Coccinelle patch to find such cases
and report them.

Inspired-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 .../find-missing-error_propagate.cocci        | 53 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 54 insertions(+)
 create mode 100644 scripts/coccinelle/find-missing-error_propagate.cocci

diff --git a/scripts/coccinelle/find-missing-error_propagate.cocci b/scripts/coccinelle/find-missing-error_propagate.cocci
new file mode 100644
index 0000000000..8b75b37b64
--- /dev/null
+++ b/scripts/coccinelle/find-missing-error_propagate.cocci
@@ -0,0 +1,53 @@
+// Find places likely missing error-propagation code, but code is too
+// complex for automatic transformation, so manual analysis is required.
+//
+// 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/find-missing-error_propagate.cocci
+//
+// Inspired by https://www.mail-archive.com/qemu-devel@nongnu.org/msg691638.html
+
+
+// First match two subsequent calls using local Error*
+// in function provided a Error** argument
+//
+@discard_func_with_errp_argument@
+typedef Error;
+Error *local_err;
+identifier func, errp, errfunc1, errfunc2;
+@@
+void func(..., Error **errp)
+{
+ <+...
+ errfunc1(..., &local_err);
+ ... when != local_err          // local_err is not used between the calls
+ errfunc2(..., &local_err);
+ ...+>
+}
+
+
+// Again, match two subsequent calls using local Error*
+// but ignoring within functions provided a Error** argument
+//
+@manual depends on never discard_func_with_errp_argument@
+Error *local_err;
+identifier errfunc1, errfunc2;
+position p;
+@@
+ errfunc1@p(..., &local_err);
+ ... when != local_err
+ errfunc2(..., &local_err);
+
+
+// As it is likely too complex to transform, report the hit
+//
+@script:python@
+f << manual.errfunc1;
+p << manual.p;
+@@
+print("[[manual check required: "
+      "error_propagate() might be missing in {}() {}:{}:{}]]".format(
+            f, p[0].file, p[0].line, p[0].column))
diff --git a/MAINTAINERS b/MAINTAINERS
index 77b93612bc..1150ec95a8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2058,6 +2058,7 @@ 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
+F: scripts/coccinelle/find-missing-error_propagate.cocci
 F: scripts/coccinelle/remove_local_err.cocci
 F: scripts/coccinelle/simplify-init-realize-error_propagate.cocci
 F: scripts/coccinelle/use-error_abort-in-instance_init.cocci
-- 
2.21.1