[RFC PATCH u-boot 02/12] sandbox: errno: avoid conflict with libc's errno

[Heinrich Schuchardt]

On 05.03.21 17:58, Simon Glass wrote:
> Hi Marek,
>
> On Fri, 5 Mar 2021 at 09:50, Marek Behun <marek.behun at nic.cz> wrote:
>>
>> On Fri, 5 Mar 2021 09:39:53 -0700
>> Simon Glass <sjg at chromium.org> wrote:
>>
>>> Hi Marek,
>>>
>>> On Fri, 5 Mar 2021 at 08:37, Marek Behun <marek.behun at nic.cz> wrote:
>>>>
>>>> On Fri, 5 Mar 2021 11:00:45 +0800
>>>> Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>
>>>>> On Wed, Mar 3, 2021 at 12:13 PM Marek Behún <marek.behun at nic.cz> wrote:
>>>>>>
>>>>>> When building with LTO, the system libc's `errno` variable used in
>>>>>> arch/sandbox/cpu/os.c conflicts with U-Boot's `errno` (defined in
>>>>>> lib/errno.c) with the following error:
>>>>>>  .../ld: errno@@GLIBC_PRIVATE: TLS definition in /lib64/libc.so.6
>>>>>>          section .tbss mismatches non-TLS reference in
>>>>>>          /tmp/u-boot.EQlEXz.ltrans0.ltrans.o
>>>>>
>>>>> Do you know if this is the expected behavior when enabling LTO on the compiler?
>>>>
>>>> I don't, but this is a bug anyway. The symbol clashes with the symbol
>>>> from glibc. Does somebody know whether the usage of this symbol in os.c
>>>> does really use glibc's version or U-Boot's one?
>>>
>>> It is intended to use glibc's version. In fact I don't think U-Boot
>>> should have an errno. We return errors in each case, as does Linux.
>>
>> The problem is that libc defines errno as a thread-local variable or,
>> in older version, as a macro expading to a function dereference, i.e.
>>   #define errno (*__get_threads_errno())
>> But U-Boot usis the errno symbol defined in include/errno.h as a symbol.
>>
>> So in order for these two symbols not to clash (in case libc is using
>> thread-local symbol with name errno), we need to rename the U-Boot
>> errno variable's symbol name.
>
> Rename is OK, but can we delete it instead? I really don't think it
> should be there.

What makes you think so?

fs/fs.c:614:            errno = -ret;

Best regards

Heinrich