Messages in this thread | | | Date | Tue, 27 Mar 2018 07:47:48 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v6] kernel.h: Retain constant expression output for max()/min() |
| |
* Kees Cook <keescook@chromium.org> wrote:
> In the effort to remove all VLAs from the kernel[1], it is desirable to > build with -Wvla. However, this warning is overly pessimistic, in that > it is only happy with stack array sizes that are declared as constant > expressions, and not constant values. One case of this is the evaluation > of the max() macro which, due to its construction, ends up converting > constant expression arguments into a constant value result. > > All attempts to rewrite this macro with __builtin_constant_p() failed with > older compilers (e.g. gcc 4.4)[2]. However, Martin Uecker constructed[3] a > mind-shattering solution that works everywhere. Cthulhu fhtagn! > > This patch updates the min()/max() macros to evaluate to a constant > expression when called on constant expression arguments. This removes > several false-positive stack VLA warnings from an x86 allmodconfig > build when -Wvla is added:
Cool!
Acked-by: Ingo Molnar <mingo@kernel.org>
How many warnings are left in an allmodconfig build?
Thanks,
Ingo
| |