[PATCH 1/2] gdb: remove dead code in make_pointer_type and make_reference_type

[PATCH 1/2] gdb: remove dead code in make_pointer_type and make_reference_type

[Tankut Baris Aktemur]

At the end of `make_pointer_type` and `make_reference_type`, GDB
updates the length of every type in the chain.  This is practically
dead code, because if we reach this point, we must have allocated a
new type.  After a new allocation, the chain contains only the
newly-created type itself.  See in `type_allocator::new_type ()`:

  type->chain = type;   /* Chain back to itself.  */

That is, we always have `ntype == ntype->chain`.  Therefore, the loop
can never be entered.  Remove it.

In `make_reference_type`, we also remove `*reftype = ntype;`, because
a few lines above the assignment was already made.  This is repeated
code.
---
 gdb/gdbtypes.c | 21 ---------------------
 1 file changed, 21 deletions(-)

diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 9098727959e..2dda175237c 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -367,8 +367,6 @@ type *
 make_pointer_type (type *type)
 {
   struct type *ntype;	/* New type */
-  struct type *chain;
-
   ntype = type->pointer_type;
 
   if (ntype)
@@ -388,14 +386,6 @@ make_pointer_type (type *type)
      gdbarch_address_to_pointer.  */
   ntype->set_is_unsigned (true);
 
-  /* Update the length of all the other variants of this type.  */
-  chain = ntype->chain;
-  while (chain != ntype)
-    {
-      chain->set_length (ntype->length ());
-      chain = chain->chain;
-    }
-
   return ntype;
 }
 
@@ -415,7 +405,6 @@ make_reference_type (type *type, type_code refcode)
 {
   struct type *ntype;	/* New type */
   struct type **reftype;
-  struct type *chain;
 
   gdb_assert (refcode == TYPE_CODE_REF || refcode == TYPE_CODE_RVALUE_REF);
 
@@ -439,16 +428,6 @@ make_reference_type (type *type, type_code refcode)
   ntype->set_length (gdbarch_ptr_bit (type->arch ()) / TARGET_CHAR_BIT);
   ntype->set_code (refcode);
 
-  *reftype = ntype;
-
-  /* Update the length of all the other variants of this type.  */
-  chain = ntype->chain;
-  while (chain != ntype)
-    {
-      chain->set_length (ntype->length ());
-      chain = chain->chain;
-    }
-
   return ntype;
 }
 
-- 
2.53.0

[PATCH 2/2] gdb: do minor code modernization in make_pointer_type and make_reference_type

[Tankut Baris Aktemur]

This is a small code modernization.  There should be no behavioral
change.
---
 gdb/gdbtypes.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 2dda175237c..409601abe03 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -366,10 +366,8 @@ smash_type (struct type *type)
 type *
 make_pointer_type (type *type)
 {
-  struct type *ntype;	/* New type */
-  ntype = type->pointer_type;
-
-  if (ntype)
+  struct type *ntype = type->pointer_type;
+  if (ntype != nullptr)
     return ntype;
 
   ntype = type_allocator (type).new_type ();
@@ -403,23 +401,22 @@ lookup_pointer_type (struct type *type)
 type *
 make_reference_type (type *type, type_code refcode)
 {
-  struct type *ntype;	/* New type */
-  struct type **reftype;
-
   gdb_assert (refcode == TYPE_CODE_REF || refcode == TYPE_CODE_RVALUE_REF);
 
-  ntype = (refcode == TYPE_CODE_REF ? type->reference_type
-	   : type->rvalue_reference_type);
+  struct type *ntype = (refcode == TYPE_CODE_REF
+			? type->reference_type
+			: type->rvalue_reference_type);
 
-  if (ntype)
+  if (ntype != nullptr)
     return ntype;
 
   ntype = type_allocator (type).new_type ();
   ntype->set_target_type (type);
-  reftype = (refcode == TYPE_CODE_REF ? &type->reference_type
-	     : &type->rvalue_reference_type);
 
-  *reftype = ntype;
+  if (refcode == TYPE_CODE_REF)
+    type->reference_type = ntype;
+  else
+    type->rvalue_reference_type = ntype;
 
   /* FIXME!  Assume the machine has only one representation for
      references, and that it matches the (only) representation for
-- 
2.53.0

Re: [PATCH 1/2] gdb: remove dead code in make_pointer_type and make_reference_type

[Simon Marchi]

On 8/3/26 10:35 AM, Tankut Baris Aktemur wrote:
> At the end of `make_pointer_type` and `make_reference_type`, GDB
> updates the length of every type in the chain.  This is practically
> dead code, because if we reach this point, we must have allocated a
> new type.  After a new allocation, the chain contains only the
> newly-created type itself.  See in `type_allocator::new_type ()`:
> 
>   type->chain = type;   /* Chain back to itself.  */
> 
> That is, we always have `ntype == ntype->chain`.  Therefore, the loop
> can never be entered.  Remove it.
> 
> In `make_reference_type`, we also remove `*reftype = ntype;`, because
> a few lines above the assignment was already made.  This is repeated
> code.

Thanks, this LGTM.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon

Re: [PATCH 2/2] gdb: do minor code modernization in make_pointer_type and make_reference_type

[Simon Marchi]

On 8/3/26 10:35 AM, Tankut Baris Aktemur wrote:
> This is a small code modernization.  There should be no behavioral
> change.

Thanks, this LGTM.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon