On 3/31/20 3:48 PM, Joseph Myers wrote:
> On Tue, 31 Mar 2020, Vineet Gupta via Libc-alpha wrote:
>
>> On 3/27/20 11:42 PM, Vineet Gupta via Libc-alpha wrote:
>>>>> +++ b/sysdeps/arc/Versions
>>>>> @@ -0,0 +1,6 @@
>>>>> +libc {
>>>>> + GLIBC_2.32 {
>>>>> + __syscall_error;
>>>>
>>>> Why does __syscall_error need a public symbol version? If it's used by a
>>>> library other than libc, that means it needs to be exported at some symbol
>>>> version - but it only needs a public version (as opposed to GLIBC_PRIVATE)
>>>> if it might be used by user programs linked with glibc (if it's used in
>>>> crt*.o, lib*_nonshared.a, or inline functions in installed headers, for
>>>> example - or in libgcc.a, libstdc++.a, etc. (GCC static libraries)).
>>>
>>> We'll historically I've preferred an out-of-line errno setter in the syscall
>>> wrappers and those are used in libpthread et all as well but not expected to be
>>> used by user programs. See my sysdeps.h
>>
>> Ok so this will not be called directly from user programs, but indeed
>> could end up in non shared libs and/or inline functions in headers, so I
>> suppose this is fine ?
>
> What inline function or object in lib*_nonshared.a / crt*.o / GCC static
> library has a reference to this symbol?
>
> If there's an inline function referring to this in an installed header, we
> can consider whether that inline function *should* be referring to it.
> Similarly if there's a reference in crt*.o / lib*_nonshared.a / GCC static
> libraries, we can consider if that reference *should* be there or if the
> function in question should actually be calling some function from libc.so
> that does the syscall there.
The assembler macros in syscall template for generating wrappers use
__syscall_error (sysdeps/unix/sysv/linux/arc/sysdep.h).
If public Version is removed, I get errors like below:
| arc-glibc-linux-gnu-gcc -shared -static-libgcc -Wl,-O1 -Wl,-z,defs -Wl,
| -dynamic-linker=/lib/ld-linux-arc.so.2 -Wl,--version-script=/SCRATCH/vgupta
| /gnu/build/glibcs/arc-linux-gnu/glibc/librt.map -Wl,-soname=librt.so.1
|
| ...
| a - mq_setattr.o
| a - librt-cancellation.o
| /SCRATCH/vgupta/gnu/install/compilers/arc-linux-gnu/lib/gcc/arc-glibc-linux-
| gnu/10.0.1/../../../../arc-glibc-linux-gnu/bin/ld: /SCRATCH/vgupta/gnu/build
| /glibcs/arc-linux-gnu/glibc/rt/librt_pic.a(mq_setattr.os): in function
| `mq_setattr':
| /SCRATCH/vgupta/gnu/src/glibc/rt/../sysdeps/unix/syscall-template.S:80:
| undefined reference to `__syscall_error'
And this change goes back to initial port (in 2016) where openssh/libcrypt.so was
failing to link somewhat similarly.
Looking as RISCV code, they opencode __syscall_error for !IS_IN (libc) which I was
hoping to avoid.
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