[PATCH 4/7] linux: Expand internal prototypes for not-cancel.h

[Adhemerval Zanella Netto]

On 31/12/24 20:13, H.J. Lu wrote:
> On Wed, Jan 1, 2025 at 4:59 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> On Wed, Jan 1, 2025 at 2:27 AM Adhemerval Zanella
>> <adhemerval.zanella@linaro.org> wrote:
>>>
>>> When building with fortify enable and with clang, internal tests
>>> that might use not-cancel fail with:
>>>
>>> ../sysdeps/unix/sysv/linux/not-cancel.h:36:10: error: reference to overloaded function could not be resolved; did you mean to call it?
>>>    36 | __typeof (open64) __open64_nocancel;
>>
>> __typeof (func) is used in many places.  Is there a way to specify a specific
>> overloaded function for Clang?
> 
> This is an issue only for functions with variable arguments.
> We should limit changes to these functions.

Yeah, it only affects variadic function because the way fortify is implemented
on clang is by implementing overloading wrappers for each possible signature.

I don't have a strong preference, you patch to limit to only variadic seems fine.
I will add a comment that __typeof should not be used in such cases on not-cancel
to avoid potential future issues.

> 
>>> because clang fortify supports relies on function overload and
>>> by having multiple function prototypes the __typeof can not
>>> find which one to use.
>>> ---
>>>  sysdeps/unix/sysv/linux/not-cancel.h | 18 +++++++++---------
>>>  1 file changed, 9 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/sysdeps/unix/sysv/linux/not-cancel.h b/sysdeps/unix/sysv/linux/not-cancel.h
>>> index 12f26912d3..3a14a407f4 100644
>>> --- a/sysdeps/unix/sysv/linux/not-cancel.h
>>> +++ b/sysdeps/unix/sysv/linux/not-cancel.h
>>> @@ -30,31 +30,31 @@
>>>  #include <sys/random.h>
>>>
>>>  /* Non cancellable open syscall.  */
>>> -__typeof (open) __open_nocancel;
>>> +int __open_nocancel (const char *, int, ...);
>>>
>>>  /* Non cancellable open syscall (LFS version).  */
>>> -__typeof (open64) __open64_nocancel;
>>> +int __open64_nocancel (const char *, int, ...);
>>>
>>>  /* Non cancellable openat syscall.  */
>>> -__typeof (openat) __openat_nocancel;
>>> +int __openat_nocancel (int, const char *, int, ...);
>>>
>>>  /* Non cacellable openat syscall (LFS version).  */
>>> -__typeof (openat64) __openat64_nocancel;
>>> +int __openat64_nocancel (int, const char *, int, ...);
>>>
>>>  /* Non cancellable read syscall.  */
>>> -__typeof (__read) __read_nocancel;
>>> +ssize_t __read_nocancel (int, void *, size_t);
>>>
>>>  /* Non cancellable pread syscall (LFS version).  */
>>> -__typeof (__pread64) __pread64_nocancel;
>>> +ssize_t __pread64_nocancel (int, void *, size_t, __off64_t);
>>>
>>>  /* Uncancelable write.  */
>>> -__typeof (__write) __write_nocancel;
>>> +ssize_t __write_nocancel (int, const void *, size_t);
>>>
>>>  /* Uncancelable close.  */
>>> -__typeof (__close) __close_nocancel;
>>> +int __close_nocancel (int);
>>>
>>>  /* Uncancelable fcntl.  */
>>> -__typeof (__fcntl) __fcntl64_nocancel;
>>> +int __fcntl64_nocancel (int, int, ...);
>>>
>>>  #if IS_IN (libc) || IS_IN (rtld)
>>>  hidden_proto (__open_nocancel)
>>> --
>>> 2.43.0
>>>
>>
>>
>> --
>> H.J.
> 
> 
>