Add new overload of gdbarch_return_value

The gdbarch "return_value" can't correctly handle variably-sized
types.  The problem here is that the TYPE_LENGTH of such a type is 0,
until the type is resolved, which requires reading memory.  However,
gdbarch_return_value only accepts a buffer as an out parameter.

Fixing this requires letting the implementation of the gdbarch method
resolve the type and return a value -- that is, both the contents and
the new type.

After an attempt at this, I realized I wouldn't be able to correctly
update all implementations (there are ~80) of this method.  So,
instead, this patch adds a new method that falls back to the current
method, and it updates gdb to only call the new method.  This way it's
possible to incrementally convert the architectures that I am able to
test.

1 files changed, 6 insertions, 0 deletions

diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h
index 9671e50..56690f0 100644
--- a/gdb/arch-utils.h
+++ b/gdb/arch-utils.h
@@ -308,4 +308,10 @@ extern void default_read_core_file_mappings
 /* Default implementation of gdbarch default_get_return_buf_addr method.  */
 extern CORE_ADDR default_get_return_buf_addr (struct type *val_typegdbarch,
 					      frame_info_ptr cur_frame);
+
+extern enum return_value_convention default_gdbarch_return_value
+     (struct gdbarch *gdbarch, struct value *function, struct type *valtype,
+      struct regcache *regcache, struct value **read_value,
+      const gdb_byte *writebuf);
+
 #endif /* ARCH_UTILS_H */