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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-27 11:04:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-27 11:04:18 -0700
commit88c5083442454e5e8a505b11fa16f32d2879651e (patch)
tree54774b7dc8cb3bf3d9cb661f63bc40fd5190fa54 /Documentation
parent43e317c1bbdfe1d4d6d19d28f925f400898d41b9 (diff)
parenta035d552a93bb9ef6048733bb9f2a0dc857ff869 (diff)
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Merge tag 'Wimplicit-fallthrough-5.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux
Pull Wimplicit-fallthrough enablement from Gustavo A. R. Silva: "This marks switch cases where we are expecting to fall through, and globally enables the -Wimplicit-fallthrough option in the main Makefile. Finally, some missing-break fixes that have been tagged for -stable: - drm/amdkfd: Fix missing break in switch statement - drm/amdgpu/gfx10: Fix missing break in switch statement With these changes, we completely get rid of all the fall-through warnings in the kernel" * tag 'Wimplicit-fallthrough-5.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux: Makefile: Globally enable fall-through warning drm/i915: Mark expected switch fall-throughs drm/amd/display: Mark expected switch fall-throughs drm/amdkfd/kfd_mqd_manager_v10: Avoid fall-through warning drm/amdgpu/gfx10: Fix missing break in switch statement drm/amdkfd: Fix missing break in switch statement perf/x86/intel: Mark expected switch fall-throughs mtd: onenand_base: Mark expected switch fall-through afs: fsclient: Mark expected switch fall-throughs afs: yfsclient: Mark expected switch fall-throughs can: mark expected switch fall-throughs firewire: mark expected switch fall-throughs
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/process/deprecated.rst14
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 49e0f64a3427..053b24a6dd38 100644
--- 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.