Create a displaced_step_closure class hierarchy

displaced_step_closure is a type defined in multiple -tdep.c files.
Trying to xfree it from the common code (infrun.c) is a problem when we
try to poison xfree for non-POD types.  Because there can be multiple of
these types in the same build, this patch makes a hierarchy of classes
with a virtual destructor.  When the common code deletes the object
through a displaced_step_closure pointer, it will invoke the right
destructor.

The amd64 used a last-member array with a variable size.  That doesn't
work with new, so I changed it for an std::vector.  Other architectures
which used a simple byte buffer as a closure now use a shared
buf_displaced_step_closure, a closure type that only contains a
gdb::byte_vector.

Reg-tested on the buildbot.

gdb/ChangeLog:

	* infrun.h: Include common/byte-vector.h.
	(struct displaced_step_closure): New struct.
	(struct buf_displaced_step_closure): New struct.
	* infrun.c (displaced_step_closure::~displaced_step_closure):
	Provide default implementation.
	(displaced_step_clear): Deallocate step closure with delete.
	* aarch64-tdep.c (displaced_step_closure): Rename to ...
	(aarch64_displaced_step_closure): ... this, extend
	displaced_step_closure.
	(aarch64_displaced_step_data) <dsc>: Change type to
	aarch64_displaced_step_closure.
	(aarch64_displaced_step_copy_insn): Adjust to type change, use
	unique_ptr.
	(aarch64_displaced_step_fixup): Add cast for displaced step
	closure.
	* amd64-tdep.c (displaced_step_closure): Rename to ...
	(amd64_displaced_step_closure): ... this, extend
	displaced_step_closure.
	<insn_buf>: Change type to std::vector<gdb_byte>.
	<max_len>: Remove.
	(fixup_riprel): Change type of DSC parameter, adjust to type
	change of insn_buf.
	(fixup_displaced_copy): Change type of DSC parameter.
	(amd64_displaced_step_copy_insn): Instantiate
	amd64_displaced_step_closure.
	(amd64_displaced_step_fixup): Add cast for closure type, adjust
	to type change of insn_buf.
	* arm-linux-tdep.c (arm_linux_cleanup_svc): Change type of
	parameter DSC.
	(arm_linux_copy_svc): Likewise.
	(cleanup_kernel_helper_return): Likewise.
	(arm_catch_kernel_helper_return): Likewise.
	(arm_linux_displaced_step_copy_insn): Instantiate
	arm_displaced_step_closure.
	* arm-tdep.c (arm_pc_is_thumb): Add cast for closure.
	(displaced_read_reg): Change type of parameter DSC.
	(branch_write_pc): Likewise.
	(load_write_pc): Likewise.
	(alu_write_pc): Likewise.
	(displaced_write_reg): Likewise.
	(arm_copy_unmodified): Likewise.
	(thumb_copy_unmodified_32bit): Likewise.
	(thumb_copy_unmodified_16bit): Likewise.
	(cleanup_preload): Likewise.
	(install_preload): Likewise.
	(arm_copy_preload): Likewise.
	(thumb2_copy_preload): Likewise.
	(install_preload_reg): Likewise.
	(arm_copy_preload_reg): Likewise.
	(cleanup_copro_load_store): Likewise.
	(install_copro_load_store): Likewise.
	(arm_copy_copro_load_store) Likewise.
	(thumb2_copy_copro_load_store): Likewise.
	(cleanup_branch): Likewise.
	(install_b_bl_blx): Likewise.
	(arm_copy_b_bl_blx): Likewise.
	(thumb2_copy_b_bl_blx): Likewise.
	(thumb_copy_b): Likewise.
	(install_bx_blx_reg): Likewise.
	(arm_copy_bx_blx_reg): Likewise.
	(thumb_copy_bx_blx_reg): Likewise.
	(cleanup_alu_imm): Likewise.
	(arm_copy_alu_imm): Likewise.
	(thumb2_copy_alu_imm): Likewise.
	(cleanup_alu_reg): Likewise.
	(install_alu_reg): Likewise.
	(arm_copy_alu_reg): Likewise.
	(thumb_copy_alu_reg): Likewise.
	(cleanup_alu_shifted_reg): Likewise.
	(install_alu_shifted_reg): Likewise.
	(arm_copy_alu_shifted_reg): Likewise.
	(cleanup_load): Likewise.
	(cleanup_store): Likewise.
	(arm_copy_extra_ld_st): Likewise.
	(install_load_store): Likewise.
	(thumb2_copy_load_literal): Likewise.
	(thumb2_copy_load_reg_imm): Likewise.
	(arm_copy_ldr_str_ldrb_strb): Likewise.
	(cleanup_block_load_all): Likewise.
	(cleanup_block_store_pc): Likewise.
	(cleanup_block_load_pc): Likewise.
	(arm_copy_block_xfer): Likewise.
	(thumb2_copy_block_xfer): Likewise.
	(cleanup_svc): Likewise.
	(install_svc): Likewise.
	(arm_copy_svc): Likewise.
	(thumb_copy_svc): Likewise.
	(arm_copy_undef): Likewise.
	(thumb_32bit_copy_undef): Likewise.
	(arm_copy_unpred): Likewise.
	(arm_decode_misc_memhint_neon): Likewise.
	(arm_decode_unconditional): Likewise.
	(arm_decode_miscellaneous): Likewise.
	(arm_decode_dp_misc): Likewise.
	(arm_decode_ld_st_word_ubyte): Likewise.
	(arm_decode_media): Likewise.
	(arm_decode_b_bl_ldmstm): Likewise.
	(arm_decode_ext_reg_ld_st): Likewise.
	(thumb2_decode_dp_shift_reg): Likewise.
	(thumb2_decode_ext_reg_ld_st): Likewise.
	(arm_decode_svc_copro): Likewise.
	(thumb2_decode_svc_copro): Likewise.
	(install_pc_relative): Likewise.
	(thumb_copy_pc_relative_16bit): Likewise.
	(thumb_decode_pc_relative_16bit): Likewise.
	(thumb_copy_pc_relative_32bit): Likewise.
	(thumb_copy_16bit_ldr_literal): Likewise.
	(thumb_copy_cbnz_cbz): Likewise.
	(thumb2_copy_table_branch): Likewise.
	(cleanup_pop_pc_16bit_all): Likewise.
	(thumb_copy_pop_pc_16bit): Likewise.
	(thumb_process_displaced_16bit_insn): Likewise.
	(decode_thumb_32bit_ld_mem_hints): Likewise.
	(thumb_process_displaced_32bit_insn): Likewise.
	(thumb_process_displaced_insn): Likewise.
	(arm_process_displaced_insn): Likewise.
	(arm_displaced_init_closure): Likewise.
	(arm_displaced_step_fixup): Add cast for closure.
	* arm-tdep.h: Include infrun.h.
	(displaced_step_closure): Rename to ...
	(arm_displaced_step_closure): ... this, extend
	displaced_step_closure.
	<u::svc::copy_svc_os>: Change type of parameter DSC.
	<cleanup>: Likewise.
	(arm_process_displaced_insn): Likewise.
	(arm_displaced_init_closure): Likewise.
	(displaced_read_reg): Likewise.
	(displaced_write_reg): Likewise.
	* i386-linux-tdep.c (i386_linux_displaced_step_copy_insn):
	Adjust.
	* i386-tdep.h: Include infrun.h.
	(i386_displaced_step_closure): New typedef.
	* i386-tdep.c (i386_displaced_step_copy_insn): Use
	i386_displaced_step_closure.
	(i386_displaced_step_fixup): Adjust.
	* rs6000-tdep.c (ppc_displaced_step_closure): New typedef.
	(ppc_displaced_step_copy_insn): Use ppc_displaced_step_closure
	and unique_ptr.
	(ppc_displaced_step_fixup): Adjust.
	* s390-linux-tdep.c (s390_displaced_step_closure): New typedef.
	(s390_displaced_step_copy_insn): Use s390_displaced_step_closure
	and unique_ptr.
	(s390_displaced_step_fixup): Adjust.

gdb/s390-linux-tdep.c

@@ -1861,6 +1861,8 @@ is_non_branch_ril (gdb_byte *insn)
   return 0;
 }
 
+typedef buf_displaced_step_closure s390_displaced_step_closure;
+
 /* Implementation of gdbarch_displaced_step_copy_insn.  */
 
 static struct displaced_step_closure *
@@ -1869,8 +1871,9 @@ s390_displaced_step_copy_insn (struct gdbarch *gdbarch,
 			       struct regcache *regs)
 {
   size_t len = gdbarch_max_insn_length (gdbarch);
-  gdb_byte *buf = (gdb_byte *) xmalloc (len);
-  struct cleanup *old_chain = make_cleanup (xfree, buf);
+  std::unique_ptr<s390_displaced_step_closure> closure
+    (new s390_displaced_step_closure (len));
+  gdb_byte *buf = closure->buf.data ();
 
   read_memory (from, buf, len);
 
@@ -1898,7 +1901,7 @@ s390_displaced_step_copy_insn (struct gdbarch *gdbarch,
 				  "RIL instruction: offset %s out of range\n",
 				  plongest (offset));
 	    }
-	  do_cleanups (old_chain);
+
 	  return NULL;
 	}
 
@@ -1914,20 +1917,21 @@ s390_displaced_step_copy_insn (struct gdbarch *gdbarch,
       displaced_step_dump_bytes (gdb_stdlog, buf, len);
     }
 
-  discard_cleanups (old_chain);
-  return (struct displaced_step_closure *) buf;
+  return closure.release ();
 }
 
 /* Fix up the state of registers and memory after having single-stepped
    a displaced instruction.  */
 static void
 s390_displaced_step_fixup (struct gdbarch *gdbarch,
-			   struct displaced_step_closure *closure,
+			   struct displaced_step_closure *closure_,
 			   CORE_ADDR from, CORE_ADDR to,
 			   struct regcache *regs)
 {
   /* Our closure is a copy of the instruction.  */
-  gdb_byte *insn = (gdb_byte *) closure;
+  s390_displaced_step_closure *closure
+    = (s390_displaced_step_closure *) closure_;
+  gdb_byte *insn = closure->buf.data ();
   static int s390_instrlen[] = { 2, 4, 4, 6 };
   int insnlen = s390_instrlen[insn[0] >> 6];