Re: [PATCH] Fix length calculation in aarch64_linux_set_debug_regs

[Simon Marchi <simon.marchi@ericsson.com>]

On 15-11-19 08:50 AM, Yao Qi wrote:
> You can push it in, with some commit log adjustments, because the old
> code is correct.

Ok I pushed it.  Again, sorry for saying the code was not correct :).


From bb82e93484cdd56c67efd52b869a6123b2623f6c Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@ericsson.com>
Date: Thu, 19 Nov 2015 10:17:36 -0500
Subject: [PATCH] Fix iov_len calculation in aarch64_linux_set_debug_regs
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There is this build failure when building in C++:

/home/simark/src/binutils-gdb/gdb/nat/aarch64-linux-hw-point.c: In function ‘void aarch64_linux_set_debug_regs(const aarch64_debug_reg_state*, int, int)’:
/home/simark/src/binutils-gdb/gdb/nat/aarch64-linux-hw-point.c:564:64: error: ‘count’ cannot appear in a constant-expression
   iov.iov_len = (offsetof (struct user_hwdebug_state, dbg_regs[count - 1])
                                                                ^
We can simplify the computation and make g++ happy at the same time by
formulating as:

  size of fixed part + size of variable part

thus...

  size of fixed part + count * size of one variable part element

thus...

  offsetof (struct user_hwdebug_state, dbg_regs) + count * sizeof (regs.dbg_reg[0]);

gdb/ChangeLog:

	* nat/aarch64-linux-hw-point.c (aarch64_linux_set_debug_regs): Change
	form of iov_len computation.
---
 gdb/ChangeLog                    | 5 +++++
 gdb/nat/aarch64-linux-hw-point.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0539d96..94721a0 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-11-19  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* nat/aarch64-linux-hw-point.c (aarch64_linux_set_debug_regs): Change
+	form of iov_len computation.
+
 2015-11-19  Pedro Alves  <palves@redhat.com>

 	* configure.ac (ERROR_ON_WARNING): Don't check whether in C++
diff --git a/gdb/nat/aarch64-linux-hw-point.c b/gdb/nat/aarch64-linux-hw-point.c
index 1a5fa6a..dcbfa98 100644
--- a/gdb/nat/aarch64-linux-hw-point.c
+++ b/gdb/nat/aarch64-linux-hw-point.c
@@ -561,8 +561,8 @@ aarch64_linux_set_debug_regs (const struct aarch64_debug_reg_state *state,
   ctrl = watchpoint ? state->dr_ctrl_wp : state->dr_ctrl_bp;
   if (count == 0)
     return;
-  iov.iov_len = (offsetof (struct user_hwdebug_state, dbg_regs[count - 1])
-		 + sizeof (regs.dbg_regs [count - 1]));
+  iov.iov_len = (offsetof (struct user_hwdebug_state, dbg_regs)
+		 + count * sizeof (regs.dbg_regs[0]));

   for (i = 0; i < count; i++)
     {
-- 
2.5.1