Introduce scoped_restore_current_inferior_for_memory

This introduces a new class,
scoped_restore_current_inferior_for_memory, and arranges to use it in
a few places.  This class is intended to handle setting up and
restoring the various globals that are needed to read or write memory
-- but without invalidating the frame cache.

I wasn't able to test the change to aix-thread.c.

Approved-By: Pedro Alves <pedro@palves.net>

3 files changed, 35 insertions, 22 deletions

diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index fbe80d6..74cc67c 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -615,13 +615,8 @@ pdc_read_data (pthdb_user_t user_current_pid, void *buf,
   /* This is needed to eliminate the dependency of current thread
      which is null so that thread reads the correct target memory.  */
   {
-    scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
-    inferior_ptid = ptid_t (user_current_pid);
-    scoped_restore_current_inferior restore_inferior;
-    set_current_inferior (inf);
-
-    scoped_restore_current_program_space restore_current_progspace;
-    set_current_program_space (inf->pspace);
+    scoped_restore_current_inferior_for_memory save_inferior
+      (inf, ptid_t (user_current_pid));
     status = target_read_memory (addr, (gdb_byte *) buf, len);
   }
   ret = status == 0 ? PDC_SUCCESS : PDC_FAILURE;
@@ -648,13 +643,8 @@ pdc_write_data (pthdb_user_t user_current_pid, void *buf,
 		user_current_pid, (long) buf, hex_string (addr), len);
 
   {
-    scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
-    inferior_ptid = ptid_t (user_current_pid);
-    scoped_restore_current_inferior restore_inferior;
-    set_current_inferior (inf);
-
-    scoped_restore_current_program_space restore_current_progspace;
-    set_current_program_space (inf->pspace);
+    scoped_restore_current_inferior_for_memory save_inferior
+      (inf, ptid_t (user_current_pid));
     status = target_write_memory (addr, (gdb_byte *) buf, len);
   }
 
diff --git a/gdb/inferior.h b/gdb/inferior.h
index caa8e4d..be76c45 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -761,6 +761,35 @@ private:
   inferior *m_saved_inf;
 };
 
+/* When reading memory from an inferior, the global inferior_ptid must
+   also be set.  This class arranges to save and restore the necessary
+   state for reading or writing memory, but without invalidating the
+   frame cache.  */
+
+class scoped_restore_current_inferior_for_memory
+{
+public:
+
+  /* Save the current globals and switch to the given inferior and the
+     inferior's program space.  PTID must name a thread in INF, it is
+     used as the new inferior_ptid.  */
+  scoped_restore_current_inferior_for_memory (inferior *inf, ptid_t ptid)
+    : m_save_ptid (&inferior_ptid)
+  {
+    set_current_inferior (inf);
+    set_current_program_space (inf->pspace);
+    inferior_ptid = ptid;
+  }
+
+  DISABLE_COPY_AND_ASSIGN (scoped_restore_current_inferior_for_memory);
+
+private:
+
+  scoped_restore_current_inferior m_save_inferior;
+  scoped_restore_current_program_space m_save_progspace;
+  scoped_restore_tmpl<ptid_t> m_save_ptid;
+};
+
 
 /* Traverse all inferiors.  */
 
diff --git a/gdb/proc-service.c b/gdb/proc-service.c
index 509836e..366e051 100644
--- a/gdb/proc-service.c
+++ b/gdb/proc-service.c
@@ -72,14 +72,8 @@ static ps_err_e
 ps_xfer_memory (const struct ps_prochandle *ph, psaddr_t addr,
 		gdb_byte *buf, size_t len, int write)
 {
-  scoped_restore_current_inferior restore_inferior;
-  set_current_inferior (ph->thread->inf);
-
-  scoped_restore_current_program_space restore_current_progspace;
-  set_current_program_space (ph->thread->inf->pspace);
-
-  scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
-  inferior_ptid = ph->thread->ptid;
+  scoped_restore_current_inferior_for_memory save_inferior (ph->thread->inf,
+							    ph->thread->ptid);
 
   CORE_ADDR core_addr = ps_addr_to_core_addr (addr);