Change type of reg_buffer::m_register_status to register_status

The type of reg_buffer::m_register_status is an array of signed char,
probably to ensure that each element takes up only one byte.  Instead,
since we use C++11, we can force the underlying type of register_status
to be signed char and use the enum type.

gdb/ChangeLog:

	* common/common-regcache.h (enum register_status): Add
	underlying type "signed char".
	* regcache.h (reg_buffer) <m_register_status>: Change type to
	register_status *.
	* regcache.c (reg_buffer::reg_buffer): Alocate arrays of
	register_status instead of signed char.
	(reg_buffer::save): Use REG_UNKNOWN instead of 0.
	(reg_buffer::get_register_status): Remove cast.
	(readable_regcache::raw_read): Remove cast.
	(readable_regcache::cooked_read): Remove cast.

gdb/ChangeLog

@@ -1,3 +1,16 @@
+2018-06-09  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* common/common-regcache.h (enum register_status): Add
+	underlying type "signed char".
+	* regcache.h (reg_buffer) <m_register_status>: Change type to
+	register_status *.
+	* regcache.c (reg_buffer::reg_buffer): Alocate arrays of
+	register_status instead of signed char.
+	(reg_buffer::save): Use REG_UNKNOWN instead of 0.
+	(reg_buffer::get_register_status): Remove cast.
+	(readable_regcache::raw_read): Remove cast.
+	(readable_regcache::cooked_read): Remove cast.
+
 2018-06-09  Tom Tromey  <tom@tromey.com>
 
 	* source.c (reverse_search_command, forward_search_command): Use

gdb/common/common-regcache.h

@@ -22,7 +22,7 @@
 
 /* This header is a stopgap until we have an independent regcache.  */
 
-enum register_status
+enum register_status : signed char
   {
     /* The register value is not in the cache, and we don't know yet
        whether it's available in the target (or traceframe).  */

gdb/regcache.c

@@ -186,13 +186,14 @@ reg_buffer::reg_buffer (gdbarch *gdbarch, bool has_pseudo)
   if (has_pseudo)
     {
       m_registers = XCNEWVEC (gdb_byte, m_descr->sizeof_cooked_registers);
-      m_register_status = XCNEWVEC (signed char,
-				    m_descr->nr_cooked_registers);
+      m_register_status
+	= XCNEWVEC (register_status, m_descr->nr_cooked_registers);
     }
   else
     {
       m_registers = XCNEWVEC (gdb_byte, m_descr->sizeof_raw_registers);
-      m_register_status = XCNEWVEC (signed char, gdbarch_num_regs (gdbarch));
+      m_register_status
+	= XCNEWVEC (register_status, gdbarch_num_regs (gdbarch));
     }
 }
 
@@ -273,7 +274,7 @@ reg_buffer::save (regcache_cooked_read_ftype *cooked_read,
   gdb_assert (m_has_pseudo);
   /* Clear the dest.  */
   memset (m_registers, 0, m_descr->sizeof_cooked_registers);
-  memset (m_register_status, 0, m_descr->nr_cooked_registers);
+  memset (m_register_status, REG_UNKNOWN, m_descr->nr_cooked_registers);
   /* Copy over any registers (identified by their membership in the
      save_reggroup) and mark them as valid.  The full [0 .. gdbarch_num_regs +
      gdbarch_num_pseudo_regs) range is checked since some architectures need
@@ -325,7 +326,7 @@ reg_buffer::get_register_status (int regnum) const
 {
   assert_regnum (regnum);
 
-  return (enum register_status) m_register_status[regnum];
+  return m_register_status[regnum];
 }
 
 void
@@ -515,7 +516,7 @@ readable_regcache::raw_read (int regnum, gdb_byte *buf)
     memcpy (buf, register_buffer (regnum),
 	    m_descr->sizeof_register[regnum]);
 
-  return (enum register_status) m_register_status[regnum];
+  return m_register_status[regnum];
 }
 
 enum register_status
@@ -609,7 +610,7 @@ readable_regcache::cooked_read (int regnum, gdb_byte *buf)
       else
 	memset (buf, 0, m_descr->sizeof_register[regnum]);
 
-      return (enum register_status) m_register_status[regnum];
+      return m_register_status[regnum];
     }
   else if (gdbarch_pseudo_register_read_value_p (m_descr->gdbarch))
     {

gdb/regcache.h

@@ -177,7 +177,7 @@ protected:
   /* The register buffers.  */
   gdb_byte *m_registers;
   /* Register cache status.  */
-  signed char *m_register_status;
+  register_status *m_register_status;
 
   friend class regcache;
   friend class detached_regcache;