Re: [PATCH v10 21/21] hash: remove use of VLAs by using standard arrays

[Andre Muezerie <andremue@linux.microsoft.com>]

On Wed, Nov 20, 2024 at 10:51:26AM +0000, Medvedkin, Vladimir wrote:
> Hi Andre,
> 
> On 20/11/2024 03:13, Andre Muezerie wrote:
> >MSVC does not support VLAs, replace VLAs with standard C arrays.
> >
> >Signed-off-by: Andre Muezerie<andremue@linux.microsoft.com>
> >---
> >  lib/hash/rte_thash_gf2_poly_math.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> >diff --git a/lib/hash/rte_thash_gf2_poly_math.c b/lib/hash/rte_thash_gf2_poly_math.c
> >index 1c62974e71..cf7c7d396c 100644
> >--- a/lib/hash/rte_thash_gf2_poly_math.c
> >+++ b/lib/hash/rte_thash_gf2_poly_math.c
> >@@ -8,6 +8,7 @@
> >  #include <rte_thash.h>
> >  #include <rte_log.h>
> >+#define MAX_POLY_DEGREE 32
> >  #define MAX_TOEPLITZ_KEY_LENGTH 64
> >  RTE_LOG_REGISTER_SUFFIX(thash_poly_logtype, thash_poly, INFO);
> >  #define RTE_LOGTYPE_HASH thash_poly_logtype
> >@@ -149,7 +150,7 @@ gf2_pow(uint32_t a, uint32_t pow, uint32_t r, int degree)
> >  static uint32_t
> >  __thash_get_rand_poly(int poly_degree)
> >  {
> >-	uint32_t roots[poly_degree];
> >+	uint32_t roots[MAX_POLY_DEGREE];
> >  	uint32_t rnd;
> >  	uint32_t ret_poly = 0;
> >  	int i, j;
> >@@ -194,7 +195,7 @@ __thash_get_rand_poly(int poly_degree)
> >  	 * Get coefficients of the polynomial for
> >  	 * (x - roots[0])(x - roots[1])...(x - roots[n])
> >  	 */
> >-	uint32_t poly_coefficients[poly_degree + 1];
> >+	uint32_t poly_coefficients[MAX_POLY_DEGREE + 1];
> >  	for (i = 0; i <= poly_degree; i++)
> >  		poly_coefficients[i] = 0;
> Since poly_coefficients is not a VLA anymore you can initializeit
> with zeros and get rid of the loop

Good observation. I'll update this.

Regards,
Andre

> >@@ -247,7 +248,7 @@ thash_get_rand_poly(uint32_t poly_degree)
> >  {
> >  	uint32_t ret_poly;
> >-	if (poly_degree > 32) {
> >+	if (poly_degree > MAX_POLY_DEGREE) {
> >  		HASH_LOG(ERR, "Wrong polynomial degree %d, must be in range [1, 32]", poly_degree);
> >  		return 0;
> >  	}
> 
> -- 
> Regards,
> Vladimir