Re: [PATCH v3] meson: Use -fno-sanitize=function when available

[Thomas Huth <thuth@redhat.com>]

On 16/08/2024 09.30, Akihiko Odaki wrote:
> On 2024/08/16 16:27, Thomas Huth wrote:
>> On 16/08/2024 09.12, Akihiko Odaki wrote:
>>> On 2024/08/16 16:03, Thomas Huth wrote:
>>>> On 16/08/2024 08.22, Akihiko Odaki wrote:
>>>>> Commit 23ef50ae2d0c (".gitlab-ci.d/buildtest.yml: Use
>>>>> -fno-sanitize=function in the clang-system job") adds
>>>>> -fno-sanitize=function for the CI but doesn't add the flag in the
>>>>> other context. Add it to meson.build for such. It is not removed from
>>>>> .gitlab-ci.d/buildtest.yml because -fno-sanitize=function in meson.build
>>>>> does not affect --extra-cflags due to argument ordering.
>>>>>
>>>>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>>>>> ---
>>>>> Changes in v3:
>>>>> - I was not properly dropping the change of .gitlab-ci.d/buildtest.yml
>>>>>    but only updated the message. v3 fixes this. (Thomas Huth)
>>>>> - Link to v2: 
>>>>> https://lore.kernel.org/r/20240729-function-v2-1-2401ab18b30b@daynix.com
>>>>>
>>>>> Changes in v2:
>>>>> - Dropped the change of: .gitlab-ci.d/buildtest.yml
>>>>> - Link to v1: 
>>>>> https://lore.kernel.org/r/20240714-function-v1-1-cc2acb4171ba@daynix.com
>>>>> ---
>>>>>   meson.build | 1 +
>>>>>   1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/meson.build b/meson.build
>>>>> index 5613b62a4f42..a4169c572ba9 100644
>>>>> --- a/meson.build
>>>>> +++ b/meson.build
>>>>> @@ -609,6 +609,7 @@ if host_os != 'openbsd' and \
>>>>>   endif
>>>>>   qemu_common_flags += cc.get_supported_arguments(hardening_flags)
>>>>> +qemu_common_flags += cc.get_supported_arguments('-fno-sanitize=function')
>>>>
>>>> As I mentioned in my last mail: I think it would make sense to move this 
>>>> at the end of the "if get_option('tsan')" block in meson.build, since 
>>>> this apparently only fixes the use of "--enable-sanitizers", and cannot 
>>>> fix the "--extra-cflags" that a user might have specified?
>>>
>>> Sorry, I missed it. It cannot fix --extra-cflags, but it should be able 
>>> to fix compiler flags specified by compiler distributor.
>>
>> Oh, you mean that there are distros that enable -fsanitize=function by 
>> default? Can you name one? If so, I think that information should go into 
>> the patch description...?
> 
> No, it is just a precaution.

Ok. I don't think any normal distro will enable this by default since this 
impacts performance of the programs, so it's either the user specifying 
--enable-sanitizers or the user specifying --extra-cflags="-fsanitize=...". 
In the latter case, your patch does not help. In the former case, I think 
this setting should go into the same code block as where we set 
-fsanitize=undefined in our meson.build file, so that it is clear where it 
belongs to.

  Thomas