Re: [PATCH 1/2] Remove a VEC from ppc-linux-nat.c

[Simon Marchi <simark@simark.ca>]

On 2019-04-27 11:23 a.m., Simon Marchi wrote:
> Hi Tom,
> 
> LGTM, I just wrote some suggestions below.
> 
> On 2019-04-27 10:31 a.m., Tom Tromey wrote:
>> @@ -1758,14 +1757,11 @@ hwdebug_point_cmp (struct ppc_hw_breakpoint *a, struct ppc_hw_breakpoint *b)
>>  static struct thread_points *
>>  hwdebug_find_thread_points_by_tid (int tid, int alloc_new)
>>  {
>> -  int i;
>> -  struct thread_points *t;
>> -
>> -  for (i = 0; VEC_iterate (thread_points_p, ppc_threads, i, t); i++)
>> +  for (thread_points *t : ppc_threads)
>>      if (t->tid == tid)
>>        return t;
> 
> Could you add braces to this for, to match our coding style?
> 
>> @@ -2392,22 +2388,22 @@ ppc_linux_thread_exit (struct thread_info *tp, int silent)
>>    int i;
>>    int tid = tp->ptid.lwp ();
>>    struct hw_break_tuple *hw_breaks;
>> -  struct thread_points *t = NULL, *p;
>> +  struct thread_points *t = NULL;
>>  
>>    if (!have_ptrace_hwdebug_interface ())
>>      return;
>>  
>> -  for (i = 0; VEC_iterate (thread_points_p, ppc_threads, i, p); i++)
>> -    if (p->tid == tid)
>> +  for (i = 0; i < ppc_threads.size (); i++)
>> +    if (ppc_threads[i].tid == tid)
>>        {
>> -	t = p;
>> +	t = &ppc_threads[i];
>>  	break;
>>        }
> 
> Here too?
> 
> I believe this loop could be a range-based one, though it also works like this.

Nevermind about this last suggestion, as the value of the `i` variable is required
below to do the removal.

But actually when looking at the code a bit closer, I am not sure it works, since
 ppc_threads[i] yields a pointer, so using the '.' operator is not valid.  And indeed:

/home/simark/src/binutils-gdb/gdb/ppc-linux-nat.c: In function 'void ppc_linux_thread_exit(thread_info*, int)':
/home/simark/src/binutils-gdb/gdb/ppc-linux-nat.c:2397:24: error: request for member 'tid' in 'ppc_threads.std::vector<_Tp, _Alloc>::operator[]<thread_points*, std::allocator<thread_points*> >(((std::vector<thread_points*>::size_type)i))', which is of pointer type '__gnu_cxx::__alloc_traits<std::allocator<thread_points*> >::value_type {aka thread_points*}' (maybe you meant to use '->' ?)
     if (ppc_threads[i].tid == tid)
                        ^~~
/home/simark/src/binutils-gdb/gdb/ppc-linux-nat.c:2399:20: error: cannot convert 'thread_points**' to 'thread_points*' in assignment
  t = &ppc_threads[i];
                    ^

Building also points out this error, where you probably meant to use .back ():

/home/simark/src/binutils-gdb/gdb/ppc-linux-nat.c: In member function 'virtual void ppc_linux_nat_target::low_new_thread(lwp_info*)':
/home/simark/src/binutils-gdb/gdb/ppc-linux-nat.c:2362:23: error: 'class std::vector<thread_points*>' has no member named 'last'; did you mean 'at'?
       p = ppc_threads.last ();
                       ^~~~

Applying this fixup to your patch makes it build for me:

From b687773f708d21e04dfe3b7d7094514d4cf8b7b7 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Sat, 27 Apr 2019 11:30:58 -0400
Subject: [PATCH] fixup

---
 gdb/ppc-linux-nat.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 45cf594ffcac..59e7ca5863f1 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -2359,7 +2359,7 @@ ppc_linux_nat_target::low_new_thread (struct lwp_info *lp)
 	return;

       /* Get a list of breakpoints from any thread.  */
-      p = ppc_threads.last ();
+      p = ppc_threads.back ();
       hw_breaks = p->hw_breaks;

       /* Copy that thread's breakpoints and watchpoints to the new thread.  */
@@ -2394,9 +2394,9 @@ ppc_linux_thread_exit (struct thread_info *tp, int silent)
     return;

   for (i = 0; i < ppc_threads.size (); i++)
-    if (ppc_threads[i].tid == tid)
+    if (ppc_threads[i]->tid == tid)
       {
-	t = &ppc_threads[i];
+	t = ppc_threads[i];
 	break;
       }

-- 
2.21.0