Re: FYI: [Ada] Rework ada_value_primitive_packed_val

[Pedro Alves <palves at redhat dot com>]

Hi Joel,

On 10/09/2015 10:41 PM, Joel Brobecker wrote:

> FYI, I have just pushed a set of commits we made a while ago at AdaCore
> after I realized ada_value_primitive_packed_val could be written in
> a way that makes it easier to understand.

I noticed that this series regressed the C++ build:

../../src/gdb/ada-lang.c: In function ‘value* ada_value_primitive_packed_val(value*, const gdb_byte*, long int, int, int, type*)’:
../../src/gdb/ada-lang.c:2553:36: error: invalid conversion from ‘void*’ to ‘gdb_byte* {aka unsigned char*}’ [-fpermissive]
       staging = malloc (staging_len);
                                    ^

(similarly for alloca.)

Looking at the code, I noticed the newly added casts, and thought of giving
it a try at eliminating them.  See patches below.  WDYT?

>From b58eef432cc9705a3e95d2cf91b0f64ae102f2e1 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Sat, 10 Oct 2015 14:31:41 +0100
Subject: [PATCH 1/2] ada-lang.c: malloc/alloca casts for C++

gdb/ChangeLog:
2015-10-10  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_value_primitive_packed_val): Add casts to malloc
	and alloca calls.
---
 gdb/ada-lang.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 97f0c49..6d1998a 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -2550,7 +2550,7 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
 	 we do, is unpack the data into a byte-aligned buffer, and then
 	 use that buffer as our object's value for resolving the type.  */
       staging_len = (bit_size + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
-      staging = malloc (staging_len);
+      staging = (gdb_byte *) malloc (staging_len);
       make_cleanup (xfree, staging);
 
       ada_unpack_from_contents (src, bit_offset, bit_size,
@@ -2581,7 +2581,7 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
       int src_len = (bit_size + bit_offset + HOST_CHAR_BIT - 1) / 8;
 
       v = value_at (type, value_address (obj) + offset);
-      src = alloca (src_len);
+      src = (gdb_byte *) alloca (src_len);
       read_memory (value_address (v), src, src_len);
     }
   else
-- 
1.9.3

>From be61a6e02fc3dce50f4ce16faa3b8a458d2a451a Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Sat, 10 Oct 2015 13:53:47 +0100
Subject: [PATCH 2/2] ada-lang.c:ada_value_primitive_packed_val: const
 correctness

gdb/ChangeLog:
2015-10-10  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_value_primitive_packed_val): Constify
	locals.  Use value_contents_writeable.  Remove casts.
---
 gdb/ada-lang.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 6d1998a..383db99 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -2525,7 +2525,7 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
                                 struct type *type)
 {
   struct value *v;
-  gdb_byte *src;                /* First byte containing data to unpack */
+  const gdb_byte *src;                /* First byte containing data to unpack */
   gdb_byte *unpacked;
   const int is_scalar = is_scalar_type (type);
   const int is_big_endian = gdbarch_bits_big_endian (get_type_arch (type));
@@ -2536,9 +2536,9 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
   type = ada_check_typedef (type);
 
   if (obj == NULL)
-    src = (gdb_byte *) valaddr + offset;
+    src = valaddr + offset;
   else
-    src = (gdb_byte *) value_contents (obj) + offset;
+    src = value_contents (obj) + offset;
 
   if (is_dynamic_type (type))
     {
@@ -2574,20 +2574,22 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
   if (obj == NULL)
     {
       v = allocate_value (type);
-      src = (gdb_byte *) valaddr + offset;
+      src = valaddr + offset;
     }
   else if (VALUE_LVAL (obj) == lval_memory && value_lazy (obj))
     {
       int src_len = (bit_size + bit_offset + HOST_CHAR_BIT - 1) / 8;
+      gdb_byte *buf;
 
       v = value_at (type, value_address (obj) + offset);
-      src = (gdb_byte *) alloca (src_len);
-      read_memory (value_address (v), src, src_len);
+      buf = (gdb_byte *) alloca (src_len);
+      read_memory (value_address (v), buf, src_len);
+      src = buf;
     }
   else
     {
       v = allocate_value (type);
-      src = (gdb_byte *) value_contents (obj) + offset;
+      src = value_contents (obj) + offset;
     }
 
   if (obj != NULL)
@@ -2610,7 +2612,7 @@ ada_value_primitive_packed_val (struct value *obj, const gdb_byte *valaddr,
     }
   else
     set_value_bitsize (v, bit_size);
-  unpacked = (gdb_byte *) value_contents (v);
+  unpacked = value_contents_writeable (v);
 
   if (bit_size == 0)
     {
-- 
1.9.3