Makefile: Globally enable fall-through warning

[sfrench/cifs-2.6.git] / Documentation / process / deprecated.rst

diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 49e0f64a3427deeec7eebf456e2549085ab378ff..053b24a6dd38cce19fc6d5ae1ed800dcb55cab00 100644 (file)
--- a/Documentation/process/deprecated.rst
+++ b/Documentation/process/deprecated.rst
@@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could
 lead to a crash, possible overwriting sensitive contents at the end of the
 stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting
 memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`)
+
+Implicit switch case fall-through
+---------------------------------
+The C language allows switch cases to "fall through" when
+a "break" statement is missing at the end of a case. This,
+however, introduces ambiguity in the code, as it's not always
+clear if the missing break is intentional or a bug. As there
+have been a long list of flaws `due to missing "break" statements
+<https://cwe.mitre.org/data/definitions/484.html>`_, we no longer allow
+"implicit fall-through". In order to identify an intentional fall-through
+case, we have adopted the marking used by static analyzers: a comment
+saying `/* Fall through */`. Once the C++17 `__attribute__((fallthrough))`
+is more widely handled by C compilers, static analyzers, and IDEs, we can
+switch to using that instead.