linux-kernel - [PATCH] selftests/resctrl: fix clang build warnings related to abs(), labs() calls

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Message-ID: <20240503023209.80787-1-jhubbard@nvidia.com>
Date: Thu,  2 May 2024 19:32:09 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Shuah Khan <shuah@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Valentin Obst <kernel@...entinobst.de>,
	linux-kselftest@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	llvm@...ts.linux.dev,
	John Hubbard <jhubbard@...dia.com>
Subject: [PATCH] selftests/resctrl: fix clang build warnings related to abs(), labs() calls

First of all, in order to build with clang at all, one must first apply
Valentin Obst's build fix for LLVM [1]. Furthermore, for this particular
resctrl directory, my pending fix [2] must also be applied. Once those
fixes are in place, then when building with clang, via:

    make LLVM=1 -C tools/testing/selftests

..two types of warnings occur:

    warning: absolute value function 'abs' given an argument of type
    'long' but has parameter of type 'int' which may cause truncation of
    value

    warning: taking the absolute value of unsigned type 'unsigned long'
    has no effect

Fix these by:

a) using labs() in place of abs(), when long integers are involved, and

b) don't call labs() unnecessarily.

[1] https://lore.kernel.org/all/20240329-selftests-libmk-llvm-rfc-v1-1-2f9ed7d1c49f@valentinobst.de/
[2] https://lore.kernel.org/all/20240503021712.78601-1-jhubbard@nvidia.com/

Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
 tools/testing/selftests/resctrl/cmt_test.c | 4 ++--
 tools/testing/selftests/resctrl/mba_test.c | 2 +-
 tools/testing/selftests/resctrl/mbm_test.c | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
index a81f91222a89..05a241519ae8 100644
--- a/tools/testing/selftests/resctrl/cmt_test.c
+++ b/tools/testing/selftests/resctrl/cmt_test.c
@@ -40,11 +40,11 @@ static int show_results_info(unsigned long sum_llc_val, int no_of_bits,
 	int ret;
 
 	avg_llc_val = sum_llc_val / num_of_runs;
-	avg_diff = (long)abs(cache_span - avg_llc_val);
+	avg_diff = (long)(cache_span - avg_llc_val);
 	diff_percent = ((float)cache_span - avg_llc_val) / cache_span * 100;
 
 	ret = platform && abs((int)diff_percent) > max_diff_percent &&
-	      abs(avg_diff) > max_diff;
+	      labs(avg_diff) > max_diff;
 
 	ksft_print_msg("%s Check cache miss rate within %lu%%\n",
 		       ret ? "Fail:" : "Pass:", max_diff_percent);
diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index 7946e32e85c8..673b2bb800f7 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -77,7 +77,7 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
 
 		avg_bw_imc = sum_bw_imc / (NUM_OF_RUNS - 1);
 		avg_bw_resc = sum_bw_resc / (NUM_OF_RUNS - 1);
-		avg_diff = (float)labs(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
+		avg_diff = (float)(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
 		avg_diff_per = (int)(avg_diff * 100);
 
 		ksft_print_msg("%s Check MBA diff within %d%% for schemata %u\n",
diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index d67ffa3ec63a..c873793d016d 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -33,7 +33,7 @@ show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span)
 
 	avg_bw_imc = sum_bw_imc / 4;
 	avg_bw_resc = sum_bw_resc / 4;
-	avg_diff = (float)labs(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
+	avg_diff = (float)(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
 	avg_diff_per = (int)(avg_diff * 100);
 
 	ret = avg_diff_per > MAX_DIFF_PERCENT;

base-commit: f03359bca01bf4372cf2c118cd9a987a5951b1c8
prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
prerequisite-patch-id: 8d96c4b8c3ed6d9ea2588ef7f594ae0f9f83c279
-- 
2.45.0