[2/3] mips: Fix SIGRTMAX definition

  MIPS support up to 96 real time signal, instead of current 95.  This
increases the NSIG value, however it does not incur in a compat
issue for older programs (which won't access the new element).
The sys_siglist is automatically expanded as well.

Checked with a mips*-linux-gnu build.
---
 sysdeps/unix/sysv/linux/mips/bits/signum-arch.h      | 2 +-
 sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist | 6 +++---
 sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist | 6 +++---
 sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist | 6 +++---
 4 files changed, 10 insertions(+), 10 deletions(-)
  

On Thu, 23 Apr 2020, Adhemerval Zanella via Libc-alpha wrote:

> MIPS support up to 96 real time signal, instead of current 95.  This
> increases the NSIG value, however it does not incur in a compat
> issue for older programs (which won't access the new element).
> The sys_siglist is automatically expanded as well.

The fact that you're changing ABI test baselines for existing symbol 
versions demonstrates that this is not a safe change (you can't change the 
size of exported data symbols without adding a new symbol version because 
of issues with copy relocations - this is what the "Symbol `%s' has 
different size in shared object, consider re-linking" message from the 
dynamic linker is about).

We have the #errlist-compat mechanism in Versions files for having 
different symbol versions for differently-sized versions of sys_errlist.  
It looks like sys_siglist has a simpler system involving OLD_SIGLIST_SIZE, 
OLD2_SIGLIST_SIZE and hardcoded version conditionals in 
sysdeps/gnu/siglist.c.  To make this change, you'll need to add some kind 
of support for having three compat versions for these symbols (so four 
versions for them in total), with different sizes, so that existing 
versions keep their existing sizes.

It will also be necessary to update 
sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist for such a new 
version in addition to the three ABI baselines changed in this patch.
  

On 23/04/2020 17:41, Joseph Myers wrote:
> On Thu, 23 Apr 2020, Adhemerval Zanella via Libc-alpha wrote:
> 
>> MIPS support up to 96 real time signal, instead of current 95.  This
>> increases the NSIG value, however it does not incur in a compat
>> issue for older programs (which won't access the new element).
>> The sys_siglist is automatically expanded as well.
> 
> The fact that you're changing ABI test baselines for existing symbol 
> versions demonstrates that this is not a safe change (you can't change the 
> size of exported data symbols without adding a new symbol version because 
> of issues with copy relocations - this is what the "Symbol `%s' has 
> different size in shared object, consider re-linking" message from the 
> dynamic linker is about).

Indeed, I forgot about copy relocations and that it is possible to link
new applications against sys_errlist.

> 
> We have the #errlist-compat mechanism in Versions files for having 
> different symbol versions for differently-sized versions of sys_errlist.  
> It looks like sys_siglist has a simpler system involving OLD_SIGLIST_SIZE, 
> OLD2_SIGLIST_SIZE and hardcoded version conditionals in 
> sysdeps/gnu/siglist.c.  To make this change, you'll need to add some kind 
> of support for having three compat versions for these symbols (so four 
> versions for them in total), with different sizes, so that existing 
> versions keep their existing sizes.

Ack, I will update the patch.

> 
> It will also be necessary to update 
> sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist for such a new 
> version in addition to the three ABI baselines changed in this patch.
> 

Ack.