From patchwork Fri Oct 6 01:22:33 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13410917 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B452A111F for ; Fri, 6 Oct 2023 01:22:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6887CC433C7; Fri, 6 Oct 2023 01:22:35 +0000 (UTC) Date: Thu, 5 Oct 2023 21:22:33 -0400 From: Steven Rostedt To: Linux Trace Devel Cc: Ross Zwisler , Stevie Alvarez Subject: [PATCH v2] libtraceeval: Have TRACEEVAL_ARRAY_SIZE() handle NULL pointer Message-ID: <20231005212233.22ae4e13@rorschach.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" In the new addition to make sure that pointers passed to traceeval_init() and other functions that require a static array and not a dynamic one will cause the build to fail, this causes NULL pointers to fail the build too. Although keys must be filled, vals are allowed to be NULL. It was assumed that: (void *)vals == NULL ? TRACEEVAL_ARRAY_SIZE(vals)) Would solve this, but it gcc was actually still giving a warning about warning: division 'sizeof (void *) / sizeof (void)' does not compute the number of array elements But now it actually fails to build with the magic check. Change TRACEEVAL_ARRAY_SIZE() to handle NULL for both keys and vals, by not only having: #define TRACEEVAL_ARRAY_SIZE(data) \ ((void *)(data) == NULL ? 0 : __TRACEEVAL_ARRAY_SIZE(data)) But that is not enough, as gcc still evaluates the second part, and it will fail to build. To handle this, change that to: #define __TRACEEVAL_ARRAY_SIZE(data) \ ((sizeof(data) / (sizeof((data)[0])) + 0) + \ The above adds " + 0" to the "sizeof((data)[0])" which quiets the warning mentioned above (the addition of zero breaks the normal pattern of finding an array size). (int)(sizeof(struct { \ int:(-!!(__builtin_types_compatible_p(typeof(data), \ typeof(&((data)[0]))) && \ (void *)(data) != NULL)); \ Added "&& (void *)(data) != NULL" that makes the above return false (zero) for a static array and NULL, which is exactly what we want. }))) Signed-off-by: Steven Rostedt (Google) Reviewed-by: Ross Zwisler --- Changes since v1: https://lore.kernel.org/all/20231005205129.6d6cbfad@gandalf.local.home/ - Fixed error in placement of parenthesis. include/traceeval.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/include/traceeval.h b/include/traceeval.h index bbf8f6ac7dd1..d8095ba5c1a1 100644 --- a/include/traceeval.h +++ b/include/traceeval.h @@ -29,13 +29,17 @@ * * struct traceeval_data keys[] = { ... }; */ -#define TRACEEVAL_ARRAY_SIZE(data) \ - ((sizeof(data) / sizeof((data)[0])) + \ +#define __TRACEEVAL_ARRAY_SIZE(data) \ + ((sizeof(data) / (sizeof((data)[0]) + 0)) + \ (int)(sizeof(struct { \ int:(-!!(__builtin_types_compatible_p(typeof(data), \ - typeof(&((data)[0]))))); \ + typeof(&((data)[0]))) && \ + (void *)(data) != NULL)); \ }))) +#define TRACEEVAL_ARRAY_SIZE(data) \ + ((void *)(data) == NULL ? 0 : __TRACEEVAL_ARRAY_SIZE(data)) + /* Data type distinguishers */ enum traceeval_data_type { TRACEEVAL_TYPE_NONE, @@ -191,7 +195,7 @@ struct traceeval; #define traceeval_init(keys, vals) \ traceeval_init_size(keys, vals, \ TRACEEVAL_ARRAY_SIZE(keys), \ - (void *)vals == NULL ? 0 : TRACEEVAL_ARRAY_SIZE(vals)) + TRACEEVAL_ARRAY_SIZE(vals)) #define traceeval_init_size(keys, vals, nr_keys, nr_vals) \ traceeval_init_data_size(keys, vals, nr_keys, nr_vals, \ @@ -211,7 +215,7 @@ int traceeval_insert_size(struct traceeval *teval, #define traceeval_insert(teval, keys, vals) \ traceeval_insert_size(teval, keys, TRACEEVAL_ARRAY_SIZE(keys), \ - vals, (void *)vals == NULL ? 0 : TRACEEVAL_ARRAY_SIZE(vals)) + vals, TRACEEVAL_ARRAY_SIZE(vals)) int traceeval_remove_size(struct traceeval *teval, const struct traceeval_data *keys, size_t nr_keys);