Re: [PATCH] gdb: fix IA64 build failure of linux-nat

[Sergei Trofimovich <slyfox@gentoo.org>]

On Mon, 17 Aug 2020 04:21:40 -0400
Simon Marchi <simark@simark.ca> wrote:

> On 2020-08-17 4:54 a.m., Tom de Vries wrote:
> > Hi,
> > 
> > IA64 support was just obsoleted in bfd (commit 73d0dc162e "Obsolete ia64").
> > 
> > So, AFAIU, this should now be built with --enable-obsolete.
> > 
> > What are the consequences for gdb IA64 patches ?
> > 
> > Thanks,
> > - Tom  
> 
> By transitivity, I'd say that the GDB port is also obsolete.  But as long as it's in
> the tree, it's fine to accept patches to keep it building (otherwise it's useless to
> keep it in the tree).
> 
> If you wanted to build GDB with --target=ia64-something-something, you'll need to pass
> --enable-obsolete in order to build BFD, which is a required dependency of GDB.  When we
> pass --enable-targets=all, it builds a GDB with ia64 support without requiring that
> --enable-obsolete flag though.
> 
> Do you know what's the BFD policy for obsolete configurations?  If they wanted to get
> rid of it completely, they would need to remove GDB support too, otherwise they'd break
> the build.  So should we eventually take the lead and remove support for it first?
> 
> Sergei, quick survey: do you, or someone you know actually use GDB on ia64?  Or you just
> noticed it not building because you package it?

I'm occasionally using gdb on ia64 for real debugging.

I'm part of the team that still keeps ia64 port alive in Gentoo.
(And also a part of team that maintains binutils and gdb).
Debian also has a functioning ia64 port and are interested to have gdb running.

gdb still comes in handy for bug squashing and poking at disassembly.

I'd like to tackle a few slightly more substantial bugs on binutils-gdb-ia64
in hopes to prolong ia64's life a bit more (if it's not much of a maintenance
burden for other ports). But I don't promise anything :)

Basic gdb support still works fine:

"""
# uname -a
Linux guppy 4.19.86-gentoo #4 SMP Fri Dec 6 23:07:34 UTC 2019 ia64 Dual-Core Intel(R) Itanium(R) Processor 9040 GenuineIntel GNU/Linux

# gdb ./a
GNU gdb (Gentoo 9.2 vanilla) 9.2
...
(gdb) start
Temporary breakpoint 1 at 0x7f1
Starting program: /root/a
Failed to read a valid object file image from memory.

Temporary breakpoint 1, 0x20000008000007f1 in main ()
(gdb) disassemble
Dump of assembler code for function main:
   0x20000008000007f0 <+0>:     [MII]       mov r2=r12
=> 0x20000008000007f1 <+1>:                 mov r14=r0;;
   0x20000008000007f2 <+2>:                 mov r8=r14
   0x2000000800000800 <+16>:    [MIB]       mov r12=r2
   0x2000000800000801 <+17>:                nop.i 0x0
   0x2000000800000802 <+18>:                br.ret.sptk.many b0;;
End of assembler dump.
"""

-- 

  Sergei