gdb: Delay releasing target_desc_up in more cases

After commit:

  commit 51a948fdf0e14fb69ab9e0c79ae8b2415801f9a3
  Date:   Mon Jul 20 14:18:04 2020 +0100

      gdb: Have allocate_target_description return a unique_ptr

There were a few places where we could (should?) have delayed
releasing the target_desc_up until a little later.  This commit
catches these cases.

In the case of ARC, the target_desc_up is now exposed right out to
gdbserver, which means making a small change there too.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* arch/aarch32.c (aarch32_create_target_description): Release the
	target_desc_up as late as possible.
	* arch/aarch64.c (aarch64_create_target_description): Likewise.
	* arch/amd64.c (amd64_create_target_description): Likewise.
	* arch/arc.c (arc_create_target_description): Return a
	target_desc_up, don't release it.
	* arch/arc.h (arc_create_target_description): Update declaration.
	(arc_lookup_target_description): Move target_desc_up into the
	cache, and return a borrowed pointer.
	* arch/arm.c (arm_create_target_description): Release the
	target_desc_up as late as possible.
	* arch/i386.c (i386_create_target_description): Likewise.
	* arch/riscv.h (riscv_create_target_description): Update
	declaration to match definition.
	* arch/tic6x.c (tic6x_create_target_description): Release the
	target_desc_up as late as possible.

gdbserver/ChangeLog:

	* linux-arc-low.cc (arc_linux_read_description): Release the
	unique_ptr returned from arc_create_target_description.

2 files changed, 8 insertions, 3 deletions

diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog
index 262ceff..79e6a37 100644
--- a/gdbserver/ChangeLog
+++ b/gdbserver/ChangeLog
@@ -1,5 +1,10 @@
 2020-10-09  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* linux-arc-low.cc (arc_linux_read_description): Release the
+	unique_ptr returned from arc_create_target_description.
+
+2020-10-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
 	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.
 
diff --git a/gdbserver/linux-arc-low.cc b/gdbserver/linux-arc-low.cc
index 1f370ef..d101bd2 100644
--- a/gdbserver/linux-arc-low.cc
+++ b/gdbserver/linux-arc-low.cc
@@ -112,12 +112,12 @@ arc_linux_read_description (void)
 #else
   arc_arch_features features (4, ARC_ISA_ARCV2);
 #endif
-  struct target_desc *tdesc = arc_create_target_description (features);
+  target_desc_up tdesc = arc_create_target_description (features);
 
   static const char *expedite_regs[] = { "sp", "status32", nullptr };
-  init_target_desc (tdesc, expedite_regs);
+  init_target_desc (tdesc.get (), expedite_regs);
 
-  return tdesc;
+  return tdesc.release ();
 }
 
 void