Re: [nft PATCH] Fix for warnings when compiling for 32bit arch

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi Phil,

On Thu, Sep 17, 2026 at 07:37:07PM +0200, Phil Sutter wrote:
> This eliminates several, probably harmless warnings when e.g. compiling
> with '-m32' for x86_64:
> 
> - Printing code assumes NFT_MAX_EXPR_LEN_BITS is unsigned long, when on
>   32bit it is unsigned int - multiply by 1UL to force the implicit type
> 
> - Pointers are unsigned long, casting to uint64_t yields a warning on
>   32bit due to the different size
> 
> - Bison tokens of type 'val' are uint64_t, print their values using
>   PRIu64 macro
> 
> - On 32bit, UINT32_MAX is of type unsigned int - cast to off_t when
>   comparing against state->indesc->line_offset to avoid different
>   signedness warning
> 
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  include/expression.h    | 2 +-
>  src/netlink_linearize.c | 4 ++--
>  src/parser_bison.y      | 2 +-
>  src/scanner.l           | 2 +-
>  4 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/expression.h b/include/expression.h
> index e6a05603552b5..b3ba4ad8d297e 100644
> --- a/include/expression.h
> +++ b/include/expression.h
> @@ -11,7 +11,7 @@
>  #include <json.h>
>  #include <libnftnl/udata.h>
>  
> -#define NFT_MAX_EXPR_LEN_BYTES (NFT_REG32_COUNT * sizeof(uint32_t))
> +#define NFT_MAX_EXPR_LEN_BYTES (1UL * NFT_REG32_COUNT * sizeof(uint32_t))

I would suggest to stick to unsigned 32-bit for this.

Related, I checked that NFT_MAX_EXPR_LEN_BITS is used with uint32_t
vars after quickly browsing code here.

Then, this is used to allocate a small buffer.

  unsigned char data[NFT_MAX_EXPR_LEN_BYTES];

Thanks.

>  #define NFT_MAX_EXPR_LEN_BITS  (NFT_MAX_EXPR_LEN_BYTES * BITS_PER_BYTE)
>  #define NFT_MAX_EXPR_RECURSION 16
>  
> diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
> index dfa841c6a407f..8de507059fe59 100644
> --- a/src/netlink_linearize.c
> +++ b/src/netlink_linearize.c
> @@ -31,7 +31,7 @@ struct nft_expr_loc *nft_expr_loc_find(const struct nftnl_expr *nle,
>  	struct nft_expr_loc *eloc;
>  	uint32_t hash;
>  
> -	hash = (uint64_t)nle % NFT_EXPR_LOC_HSIZE;
> +	hash = (unsigned long)nle % NFT_EXPR_LOC_HSIZE;
>  	list_for_each_entry(eloc, &ctx->expr_loc_htable[hash], hlist) {
>  		if (eloc->nle == nle)
>  			return eloc;
> @@ -50,7 +50,7 @@ static void nft_expr_loc_add(const struct nftnl_expr *nle,
>  	eloc = xmalloc(sizeof(*eloc));
>  	eloc->nle = nle;
>  	eloc->loc = loc;
> -	hash = (uint64_t)nle % NFT_EXPR_LOC_HSIZE;
> +	hash = (unsigned long)nle % NFT_EXPR_LOC_HSIZE;
>  	list_add_tail(&eloc->hlist, &ctx->expr_loc_htable[hash]);
>  }
>  
> diff --git a/src/parser_bison.y b/src/parser_bison.y
> index 6e1c1cc205331..138dbfa3b70de 100644
> --- a/src/parser_bison.y
> +++ b/src/parser_bison.y
> @@ -5887,7 +5887,7 @@ payload_expr		:	payload_raw_expr
>  payload_raw_len		:	NUM
>  			{
>  				if ($1 > NFT_MAX_EXPR_LEN_BITS) {
> -					erec_queue(error(&@1, "raw payload length %lu exceeds upper limit of %lu",
> +					erec_queue(error(&@1, "raw payload length %" PRIu64 " exceeds upper limit of %lu",
>  							 $1, NFT_MAX_EXPR_LEN_BITS),
>  						 state->msgs);
>  					YYERROR;
> diff --git a/src/scanner.l b/src/scanner.l
> index 61fcc4fa3bad3..37729ebc3cc55 100644
> --- a/src/scanner.l
> +++ b/src/scanner.l
> @@ -91,7 +91,7 @@ static void update_offset(struct parser_state *state, struct location *loc,
>  	uint32_t line_offset;
>  
>  	state->indesc->token_offset	+= len;
> -	if (state->indesc->line_offset > UINT32_MAX)
> +	if (state->indesc->line_offset > (off_t)UINT32_MAX)
>  		line_offset = UINT32_MAX;
>  	else
>  		line_offset = state->indesc->line_offset;
> -- 
> 2.54.0
>