Date: Thu, 25 Apr 2024 08:39:52 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Nathan Chancellor <nathan@...nel.org>, shuah@...nel.org
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Thomas Gleixner <tglx@...utronix.de>, brauner@...nel.org,
 akpm@...ux-foundation.org, linux-mm@...ck.org, fenghua.yu@...el.com,
 reinette.chatre@...el.com, anna-maria@...utronix.de, frederic@...nel.org,
 jstultz@...gle.com, sboyd@...nel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2 00/10] selftests: Make ksft_exit functions return void
 instead of int

On 4/24/24 11:24, Nathan Chancellor wrote:
> Hi all,
> 
> Commit f7d5bcd35d42 ("selftests: kselftest: Mark functions that
> unconditionally call exit() as __noreturn") marked functions that call
> exit() as __noreturn but it did not change the return type of these
> functions from 'void' to 'int' like it should have (since a noreturn
> function by definition cannot return an integer because it does not
> return...) because there are many tests that return the result of the
> ksft_exit function, even though it has never been used due to calling
> exit().
> 
> Prior to adding __noreturn, the compiler would not know that the functions
> that call exit() will not return, so code like
> 
>    void ksft_exit_fail(void)
>    {
>      exit(1);
>    }
> 
>    void ksft_exit_pass(void)
>    {
>      exit(0);
>    }
> 
>    int main(void)
>    {
>      int ret;
> 
>      ret = foo();
>      if (ret)
>        ksft_exit_fail();
>      ksft_exit_pass();
>    }
> 
> would cause the compiler to complain that main() does not return an
> integer, even though when ksft_exit_pass() is called, exit() will cause
> the program to terminate. So ksft_exit_...() returns int to make the
> compiler happy.
> 
>    int ksft_exit_fail(void)
>    {
>      exit(1);
>    }
> 
>    int ksft_exit_pass(void)
>    {
>      exit(0);
>    }
> 
>    int main(void)
>    {
>      int ret;
> 
>      ret = foo();
>      if (ret)
>        return ksft_exit_fail();
>      return ksft_exit_pass();
>    }
> 
> While this results in no warnings, it is weird semantically and it has
> issues as noted in the aforementioned __noreturn change. Now that
> __noreturn has been added to these functions, it is much cleaner to
> change the functions to 'void' and eliminate the return statements, as
> it has been made clear to the compiler that these functions terminate
> the program. Drop the return before all instances of ksft_exit_...() in
> a mostly mechanical way.
> 
> ---
> Changes in v2:
> - Split series into individual patches per subsystem at Shuah's
>    request and CC maintainers for subsystems that have one.
> - Rewrite commit messages for new patches and move previous commit
>    message into cover letter to high level explain all changes.
> - Carry forward Thomas and Muhammad's review on patch split, as there
>    were no functional changes, please holler if this was inappropriate.

Thank you for carrying the reviewed by tags.

> - Link to v1: https://lore.kernel.org/r/20240417-ksft-exit-int-to-void-v1-1-eff48fdbab39@kernel.org
> 
> ---
> Nathan Chancellor (10):
>        selftests/clone3: ksft_exit functions do not return
>        selftests/ipc: ksft_exit functions do not return
>        selftests: membarrier: ksft_exit_pass() does not return
>        selftests/mm: ksft_exit functions do not return
>        selftests: pidfd: ksft_exit functions do not return
>        selftests/resctrl: ksft_exit_skip() does not return
>        selftests: sync: ksft_exit_pass() does not return
>        selftests: timers: ksft_exit functions do not return
>        selftests: x86: ksft_exit_pass() does not return
>        selftests: kselftest: Make ksft_exit functions return void instead of int
> 

Applied to linux-kselftest next for Linux 6.10-rc1.

thanks,
-- Shuah

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