Add a description, an example and a couple of options when it is safe
to ignore it.
Signed-off-by: Martin Fernandez <martin.fernandez@xxxxxxxxxxxxx>
---
Documentation/dev-tools/checkpatch.rst | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index c3389c6f3838..678c1956468b 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -854,6 +854,32 @@ Macros, Attributes and Symbols
...
}
+ **MACRO_ARG_REUSE**
+ Using the same argument multiple times in the macro definition
+ may lead to unwanted side effects.
+
+ For example, given a min() macro defined like::
+
+ #define min(x, y) ((x) < (y) ? (x) : (y))
+
+ If you call it with ``min(foo(x), 0)``, it would expand to::
+
+ foo(x) < 0 ? foo(x) : 0
+
+ If foo has side effects or it's an expensive calculation the
+ results might not be what the user intended.
+
+ When it's safe to ignore:
+
+ - If the macro arguments of all uses of this macro are free of
+ unintended side effects. Passing a constant value is usually
+ fine, as the compiler will use constant propagation and further
+ optimizations to produce acceptable code.
+
+ - If you defined local variables that will hold the value of each
+ argument in the macro's definition. See the min() macro in
+ include/linux/minmax.h for example.
+
**MISPLACED_INIT**
It is possible to use section markers on variables in a way
which gcc doesn't understand (or at least not the way the
--
2.30.2
