[PATCH] arc: Fix gcc-4.8 compilation failure for arc.c

[PATCH] arc: Fix gcc-4.8 compilation failure for arc.c

[Shahab Vahedi via Gdb-patches]

From: Shahab Vahedi <shahab@synopsys.com>

Building an arc target:

$ configulre --target=arc-elf32                \
             --enable-targets=arc-linux-uclibc \
	     ...

On a system with gcc-4.8 (CentOS 7.x), fails with:
--------8<---------
../../gdb/arch/arc.c:117:43:   required from here
/usr/include/c++/4.8.2/bits/hashtable_policy.h:195:39: error: no matching
function for call to 'std::pair<const arc_arch_features, const
std::unique_ptr<target_desc, target_desc_deleter> >::pair(const
arc_arch_features&, target_desc*&)'
  : _M_v(std::forward<_Args>(__args)...) { }
                                       ^
/usr/include/c++/4.8.2/bits/hashtable_policy.h:195:39: note: candidates are:
In file included from /usr/include/c++/4.8.2/utility:70:0,
                 from /usr/include/c++/4.8.2/tuple:38,
                 from /usr/include/c++/4.8.2/functional:55,
                 from ../../gdb/../gdbsupport/ptid.h:35,
                 from ../../gdb/../gdbsupport/common-defs.h:123,
                 from ../../gdb/arch/arc.c:19:
/usr/include/c++/4.8.2/bits/stl_pair.h:206:9: note: template<class ...
_Args1, long unsigned int ..._Indexes1, class ... _Args2, long unsigned int
..._Indexes2> std::pair<_T1, _T2>::pair(std::tuple<_Args1 ...>&,
std::tuple<_Args2 ...>&, std::_Index_tuple<_Indexes1 ...>,
std::_Index_tuple<_Indexes2 ...>)
         pair(tuple<_Args1...>&, tuple<_Args2...>&,
         ^
-------->8---------

The corresponding line in arc.c must use an explicit ctor:
--------8<---------
 arc_lookup_target_description (...)
 {

   /* Add the newly created target description to the repertoire.  */
-  arc_tdesc_cache.emplace (features, tdesc);
+  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));

   return tdesc;
 }
-------->8---------
See "PR gcc/96537" for more details.

Last but not least, this problem has originally been investigated
by Tom de Vries for RISCV targets (see 38f8aa06d9).

gdb/ChangeLog:

	PR build/27385
	* arch/arc.c (arc_lookup_target_description): Use an explicit ctor.
---
 gdb/arch/arc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gdb/arch/arc.c b/gdb/arch/arc.c
index 3808f9fe292..4f2595b9c35 100644
--- a/gdb/arch/arc.c
+++ b/gdb/arch/arc.c
@@ -113,8 +113,9 @@ arc_lookup_target_description (const struct arc_arch_features &features)
 
   target_desc *tdesc = arc_create_target_description (features);
 
-  /* Add the newly created target description to the repertoire.  */
-  arc_tdesc_cache.emplace (features, tdesc);
+  /* Add the newly created target description to the repertoire.
+     PR build/27385: Use "target_desc_up ()" ctor explicitly.  */
+  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));
 
   return tdesc;
 }
-- 
2.30.0

Re: [PATCH] arc: Fix gcc-4.8 compilation failure for arc.c

[Tom Tromey]

Shahab>    target_desc *tdesc = arc_create_target_description (features);
 
Shahab> -  /* Add the newly created target description to the repertoire.  */
Shahab> -  arc_tdesc_cache.emplace (features, tdesc);
Shahab> +  /* Add the newly created target description to the repertoire.
Shahab> +     PR build/27385: Use "target_desc_up ()" ctor explicitly.  */
Shahab> +  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));
 
Shahab>    return tdesc;

I was going to suggest that arc_create_target_description return a
target_desc_up, but when I look at the code, I see it already does, and
that this line is different:

  arc_tdesc_cache.emplace (features, std::move (tdesc));

So I suspect this is already fixed.

Tom

Re: [PATCH] arc: Fix gcc-4.8 compilation failure for arc.c

[Shahab Vahedi via Gdb-patches]

On Tue, Feb 09, 2021 at 07:52:42AM -0700, Tom Tromey wrote:
> Shahab>    target_desc *tdesc = arc_create_target_description (features);
>  
> Shahab> -  /* Add the newly created target description to the repertoire.  */
> Shahab> -  arc_tdesc_cache.emplace (features, tdesc);
> Shahab> +  /* Add the newly created target description to the repertoire.
> Shahab> +     PR build/27385: Use "target_desc_up ()" ctor explicitly.  */
> Shahab> +  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));
>  
> Shahab>    return tdesc;
> 
> I was going to suggest that arc_create_target_description return a
> target_desc_up, but when I look at the code, I see it already does, and
> that this line is different:
> 
>   arc_tdesc_cache.emplace (features, std::move (tdesc));
> 
> So I suspect this is already fixed.

It is fixed in the trunk [1][2].  However, those are big patches.
I think it is better (safer?) to keep the fix small like the one
for RISCV [3].


Cheers,
Shahab


[1] gdb: Have allocate_target_description return a unique_ptr
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=51a948fdf0e

[2] gdb: Delay releasing target_desc_up in more cases
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=bbb826f5e92

[3] [gdb/build] Fix missing implicit constructor call with gcc 4.8
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=38f8aa06d9c

Re: [PATCH] arc: Fix gcc-4.8 compilation failure for arc.c

[Tom Tromey]

Shahab> It is fixed in the trunk [1][2].  However, those are big patches.
Shahab> I think it is better (safer?) to keep the fix small like the one
Shahab> for RISCV [3].

We discussed on irc -- it wasn't clear to me that this was intended for
the gdb 10 branch.  The patch looks ok to me.  Thanks.

Tom

[PUSHED gdb-10-branch] arc: Fix gcc-4.8 compilation failure for arc.c

[Shahab Vahedi via Gdb-patches]

From: Shahab Vahedi <shahab@synopsys.com>

Building an arc target:

$ configulre --target=arc-elf32                \
             --enable-targets=arc-linux-uclibc \
	     ...

On a system with gcc-4.8 (CentOS 7.x), fails with:
--------8<---------
../../gdb/arch/arc.c:117:43:   required from here
/usr/include/c++/4.8.2/bits/hashtable_policy.h:195:39: error: no matching
function for call to 'std::pair<const arc_arch_features, const
std::unique_ptr<target_desc, target_desc_deleter> >::pair(const
arc_arch_features&, target_desc*&)'
  : _M_v(std::forward<_Args>(__args)...) { }
                                       ^
/usr/include/c++/4.8.2/bits/hashtable_policy.h:195:39: note: candidates are:
In file included from /usr/include/c++/4.8.2/utility:70:0,
                 from /usr/include/c++/4.8.2/tuple:38,
                 from /usr/include/c++/4.8.2/functional:55,
                 from ../../gdb/../gdbsupport/ptid.h:35,
                 from ../../gdb/../gdbsupport/common-defs.h:123,
                 from ../../gdb/arch/arc.c:19:
/usr/include/c++/4.8.2/bits/stl_pair.h:206:9: note: template<class ...
_Args1, long unsigned int ..._Indexes1, class ... _Args2, long unsigned int
..._Indexes2> std::pair<_T1, _T2>::pair(std::tuple<_Args1 ...>&,
std::tuple<_Args2 ...>&, std::_Index_tuple<_Indexes1 ...>,
std::_Index_tuple<_Indexes2 ...>)
         pair(tuple<_Args1...>&, tuple<_Args2...>&,
         ^
-------->8---------

The corresponding line in arc.c must use an explicit ctor:
--------8<---------
 arc_lookup_target_description (...)
 {

   /* Add the newly created target description to the repertoire.  */
-  arc_tdesc_cache.emplace (features, tdesc);
+  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));

   return tdesc;
 }
-------->8---------
See "PR gcc/96537" for more details.

Last but not least, this problem has originally been investigated
by Tom de Vries for RISCV targets (see 38f8aa06d9).

gdb/ChangeLog:

	PR build/27385
	* arch/arc.c (arc_lookup_target_description): Use
	target_desc_up() ctor explicitly.
---
 gdb/ChangeLog  | 6 ++++++
 gdb/arch/arc.c | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9d12c466952..d33bf67c483 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2021-02-09  Shahab Vahedi  <shahab@synopsys.com>
+
+	PR build/27385
+	* arch/arc.c (arc_lookup_target_description): Use
+	target_desc_up() ctor explicitly.
+
 2021-02-08  Shahab Vahedi  <shahab@synopsys.com>
 
 	PR tdep/27369
diff --git a/gdb/arch/arc.c b/gdb/arch/arc.c
index d80d2fe4c0d..24d08179c85 100644
--- a/gdb/arch/arc.c
+++ b/gdb/arch/arc.c
@@ -113,8 +113,9 @@ arc_lookup_target_description (const struct arc_arch_features &features)
 
   target_desc *tdesc = arc_create_target_description (features);
 
-  /* Add the newly created target description to the repertoire.  */
-  arc_tdesc_cache.emplace (features, tdesc);
+  /* Add the newly created target description to the repertoire.
+     PR build/27385: Use "target_desc_up ()" ctor explicitly.  */
+  arc_tdesc_cache.emplace (features, target_desc_up (tdesc));
 
   return tdesc;
 }
-- 
2.30.0