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| author | Kees Cook <keescook@chromium.org> | 2020-06-15 12:06:11 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2020-07-16 12:32:24 -0700 |
| commit | 4b19bec97c882da09f7fd600895e0df1534a58dc (patch) | |
| tree | 316763ce483a04fb01022cea79f52fd3957e9efd /Documentation/process | |
| parent | 9ebcfadb0610322ac537dd7aa5d9cbc2b2894c68 (diff) | |
| download | lwn-4b19bec97c882da09f7fd600895e0df1534a58dc.tar.gz lwn-4b19bec97c882da09f7fd600895e0df1534a58dc.zip | |
docs: deprecated.rst: Add uninitialized_var()
Nothing should be using this macro, and the entire idea of tricking the
compiler into silencing such warnings is a mistake.
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Joe Perches <joe@perches.com>
Cc: linux-doc@vger.kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'Documentation/process')
| -rw-r--r-- | Documentation/process/deprecated.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst index 652e2aa02a66..943a926ecbbb 100644 --- a/Documentation/process/deprecated.rst +++ b/Documentation/process/deprecated.rst @@ -51,6 +51,24 @@ to make sure their systems do not continue running in the face of "unreachable" conditions. (For example, see commits like `this one <https://git.kernel.org/linus/d4689846881d160a4d12a514e991a740bcb5d65a>`_.) +uninitialized_var() +------------------- +For any compiler warnings about uninitialized variables, just add +an initializer. Using the uninitialized_var() macro (or similar +warning-silencing tricks) is dangerous as it papers over `real bugs +<https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/>`_ +(or can in the future), and suppresses unrelated compiler warnings +(e.g. "unused variable"). If the compiler thinks it is uninitialized, +either simply initialize the variable or make compiler changes. Keep in +mind that in most cases, if an initialization is obviously redundant, +the compiler's dead-store elimination pass will make sure there are no +needless variable writes. + +As Linus has said, this macro +`must <https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/>`_ +`be <https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/>`_ +`removed <https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/>`_. + open-coded arithmetic in allocator arguments -------------------------------------------- Dynamic size calculations (especially multiplication) should not be |