[PATCH v2 3/3] eal: replace out of bounds VLA with static_assert

[Morten Brørup]

> From: Tyler Retzlaff [mailto:roretzla at linux.microsoft.com]
> Sent: Friday, 16 February 2024 01.34
> 
> ping
> 
> i'd like to see this change go in asap since it is pre-requisite to
> turning on -Wvla which explicitly caught use of non-constant
> expressions
> in the RTE_BUILD_BUG_ON() hiding bugs.
> 
> thanks!
> 
> On Mon, Nov 13, 2023 at 09:06:05AM -0800, Stephen Hemminger wrote:
> > Both Gcc, clang and MSVC have better way to do compile time
> > assertions rather than using out of bounds array access.
> > The old method would fail if -Wvla is enabled because compiler
> > can't determine size in that code.  Also, the use of new
> > _Static_assert will catch broken code that is passing non-constant
> > expression to RTE_BUILD_BUG_ON().
> >
> > Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> > Acked-by: Morten Brørup <mb at smartsharesystems.com>
> > Acked-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> > ---
> >  lib/eal/include/rte_common.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/eal/include/rte_common.h
> b/lib/eal/include/rte_common.h
> > index c1ba32d00e47..bea7c0e57d5e 100644
> > --- a/lib/eal/include/rte_common.h
> > +++ b/lib/eal/include/rte_common.h
> > @@ -16,6 +16,7 @@
> >  extern "C" {
> >  #endif
> >
> > +#include <assert.h>
> >  #include <stdint.h>
> >  #include <limits.h>
> >
> > @@ -495,7 +496,7 @@ rte_is_aligned(const void * const __rte_restrict
> ptr, const unsigned int align)
> >  /**
> >   * Triggers an error at compilation time if the condition is true.
> >   */
> > -#define RTE_BUILD_BUG_ON(condition) ((void)sizeof(char[1 -
> 2*!!(condition)]))
> > +#define RTE_BUILD_BUG_ON(condition) static_assert(!(condition),
> #condition)
> >
> >  /*********** Cache line related macros ********/
> >
> > --
> > 2.39.2

Reviewed-by: Morten Brørup <mb at smartsharesystems.com>