Re: [PATCHv2] selftests: timens: exec: use 'labs()' over 'abs()'

On Wed, Nov 10, 2021 at 12:09 PM Nick Desaulniers ndesaulniers@google.com wrote:

On Wed, Nov 10, 2021 at 10:04 AM Anders Roxell anders.roxell@linaro.org wrote:

...

When building selftests/timens with clang, the compiler warn about the function abs() see below:

exec.c:33:8: error: absolute value function 'abs' given an argument of type 'long' but has parameter of type 'int' which may cause truncation of value [-Werror,-Wabsolute-value] if (abs(tst.tv_sec - now.tv_sec) > 5) ^ exec.c:33:8: note: use function 'labs' instead if (abs(tst.tv_sec - now.tv_sec) > 5) ^~~ labs

Rework to store the time difference in a 'long long' and pass that to llabs(), since the variable can be an 'int', 'long' or 'long long' depending on the architecture and C library.

Suggested-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Anders Roxell anders.roxell@linaro.org

Thanks for the patch! Reviewed-by: Nick Desaulniers ndesaulniers@google.com

ah, gmail doesn't do a great job at showing the subject when a v2 is sent in-reply-to. Should the oneline mention llabs rather than labs now?

...

---

tools/testing/selftests/timens/exec.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/timens/exec.c b/tools/testing/selftests/timens/exec.c index e40dc5be2f66..04439e6ac8a2 100644 --- a/tools/testing/selftests/timens/exec.c +++ b/tools/testing/selftests/timens/exec.c @@ -21,6 +21,7 @@ int main(int argc, char *argv[]) { struct timespec now, tst;

•   long long timediff;
    int status, i;
    pid_t pid;
  
  

@@ -30,7 +31,8 @@ int main(int argc, char *argv[])

            for (i = 0; i < 2; i++) {
                    _gettime(CLOCK_MONOTONIC, &tst, i);

•                   if (abs(tst.tv_sec - now.tv_sec) > 5)
  

•                   timediff = tst.tv_sec - now.tv_sec;
  

•                   if (llabs(timediff) > 5)
                            return pr_fail("%ld %ld\n", now.tv_sec, tst.tv_sec);
            }
            return 0;
  

@@ -50,7 +52,8 @@ int main(int argc, char *argv[])

    for (i = 0; i < 2; i++) {
            _gettime(CLOCK_MONOTONIC, &tst, i);

•           if (abs(tst.tv_sec - now.tv_sec) > 5)
  

•           timediff = tst.tv_sec - now.tv_sec;
  

•           if (llabs(timediff) > 5)
                    return pr_fail("%ld %ld\n",
                                    now.tv_sec, tst.tv_sec);
    }
  

@@ -70,7 +73,8 @@ int main(int argc, char *argv[]) /* Check that a child process is in the new timens. */ for (i = 0; i < 2; i++) { _gettime(CLOCK_MONOTONIC, &tst, i);

•                   if (abs(tst.tv_sec - now.tv_sec - OFFSET) > 5)
  

•                   timediff = tst.tv_sec - now.tv_sec - OFFSET;
  

•                   if (llabs(timediff) > 5)
                            return pr_fail("%ld %ld\n",
                                            now.tv_sec + OFFSET, tst.tv_sec);
            }
  

-- 2.33.0

-- Thanks, ~Nick Desaulniers