| Message ID | 20200620033007.1444705-2-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | Remove uninitialized_var() macro | expand |
On Fri, Jun 19, 2020 at 8:30 PM Kees Cook <keescook@chromium.org> wrote: > > Nothing should be using this macro, and the entire idea of tricking the > compiler into silencing such warnings is a mistake. > > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > --- > Documentation/process/deprecated.rst | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > 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 > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200620033007.1444705-2-keescook%40chromium.org.
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
Nothing should be using this macro, and the entire idea of tricking the compiler into silencing such warnings is a mistake. Signed-off-by: Kees Cook <keescook@chromium.org> --- Documentation/process/deprecated.rst | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)