gdb: add accessors for field (and call site) location

Add accessors for the various location values in struct field.  This
lets us assert that when we get a location value of a certain kind (say,
bitpos), the field's location indeed contains a value of that kind.

Remove the SET_FIELD_* macros, instead use the new setters directly.
Update the FIELD_* macros used to access field locations to go through
the getters.  They will be removed in a subsequent patch.

There are places where the FIELD_* macros are used on call_site_target
structures, because it contains members of the same name (loc_kind and
loc).  For now, I have replicated the getters/setters in
call_site_target.  But we could perhaps eventually factor them in a
"location" structure that can be used at both places.

Note that the field structure, being zero-initialized, defaults to a
bitpos location with value 0.  While writing this patch, I tried to make
it default to an "unset" location, to catch places where we would miss
setting a field's location.  However, I found that some places relied on
the default being "bitpos 0", so I left it as-is.  This change could
always be done as follow-up work, making these places explicitly set the
"bitpos 0" location.

I found two issues to fix:

 - I got some failures in the gdb.base/infcall-nested-structs-c++.exp
   test.  They were caused by two functions in amd64-tdep.c using
   TYPE_FIELD_BITPOS before checking if the location is of the bitpos
   kind, which they do indirectly through `field_is_static`.  Simply
   move getting the bitpos below the field_is_static call.

 - I got a failure in gdb.xml/tdesc-regs.exp.  It turns out that in
   make_gdb_type_enum, we set enum field values using SET_FIELD_BITPOS,
   and later access them through FIELD_ENUMVAL.  Fix that by using
   set_loc_enumval to set the value.

Change-Id: I53d3734916c46457576ba11dd77df4049d2fc1e8

1 files changed, 6 insertions, 5 deletions

diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 129f07e598d..47761208088 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -553,7 +553,6 @@ amd64_has_unaligned_fields (struct type *type)
       for (int i = 0; i < type->num_fields (); i++)
 	{
 	  struct type *subtype = check_typedef (type->field (i).type ());
-	  int bitpos = TYPE_FIELD_BITPOS (type, i);
 
 	  /* Ignore static fields, empty fields (for example nested
 	     empty structures), and bitfields (these are handled by
@@ -564,6 +563,8 @@ amd64_has_unaligned_fields (struct type *type)
 	      || TYPE_FIELD_PACKED (type, i))
 	    continue;
 
+	  int bitpos = TYPE_FIELD_BITPOS (type, i);
+
 	  if (bitpos % 8 != 0)
 	    return true;
 
@@ -592,21 +593,21 @@ amd64_classify_aggregate_field (struct type *type, int i,
 				unsigned int bitoffset)
 {
   struct type *subtype = check_typedef (type->field (i).type ());
-  int bitpos = bitoffset + TYPE_FIELD_BITPOS (type, i);
-  int pos = bitpos / 64;
   enum amd64_reg_class subclass[2];
   int bitsize = TYPE_FIELD_BITSIZE (type, i);
-  int endpos;
 
   if (bitsize == 0)
     bitsize = TYPE_LENGTH (subtype) * 8;
-  endpos = (bitpos + bitsize - 1) / 64;
 
   /* Ignore static fields, or empty fields, for example nested
      empty structures.*/
   if (field_is_static (&type->field (i)) || bitsize == 0)
     return;
 
+  int bitpos = bitoffset + TYPE_FIELD_BITPOS (type, i);
+  int pos = bitpos / 64;
+  int endpos = (bitpos + bitsize - 1) / 64;
+
   if (subtype->code () == TYPE_CODE_STRUCT
       || subtype->code () == TYPE_CODE_UNION)
     {