Re: [PATCH] [gdb/build] Fix build breaker with -std=c++11

[Tom de Vries <tdevries@suse.de>]

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On 8/7/23 16:35, Simon Marchi wrote:
> 
> 
> On August 6, 2023 7:59:15 p.m. EDT, Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:
>> When building with -std=c++11 I run into:
>> ...
>> gdb/dwarf2/cooked-index.c: In member function \
>>   ‘void cooked_index::start_writing_index(dwarf2_per_bfd*)’:
>> gdb/dwarf2/cooked-index.c:469:10: error: lambda capture initializers only \
>>   available with -std=c++14 or -std=gnu++14 [-Werror]
>>           ctx = std::move (ctx)] ()
>>           ^~~
>> ...
>>
>> Fix this by capturing a copy instead:
>> ...
>>     = gdb::thread_pool::g_thread_pool->post_task ([this, per_bfd, ctx] ()
>> ...
>>
>> Tested on x86_64-linux.
>>
>> Reported-By: Tom Tromey <tom@tromey.com>
> 
> When we encounter things like this, should we add some greppable TODO comment to record an actionable item for when we switch to a more recent C++ version?

Hi Simon,

thanks for the review.

Fine by me, added comment.

Thanks,
- Tom

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From ef0b55aaf4eaa9a1efece7656df1a8a997f97412 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Mon, 7 Aug 2023 00:31:04 +0200
Subject: [PATCH] [gdb/build] Fix build breaker with -std=c++11
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When building with -std=c++11 I run into:
...
gdb/dwarf2/cooked-index.c: In member function \
  ‘void cooked_index::start_writing_index(dwarf2_per_bfd*)’:
gdb/dwarf2/cooked-index.c:469:10: error: lambda capture initializers only \
  available with -std=c++14 or -std=gnu++14 [-Werror]
          ctx = std::move (ctx)] ()
          ^~~
...

Fix this by capturing a copy instead:
...
    = gdb::thread_pool::g_thread_pool->post_task ([this, per_bfd, ctx] ()
...

Tested on x86_64-linux.

Reported-By: Tom Tromey <tom@tromey.com>
---
 gdb/dwarf2/cooked-index.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/gdb/dwarf2/cooked-index.c b/gdb/dwarf2/cooked-index.c
index df82e86b690..775b1383ce5 100644
--- a/gdb/dwarf2/cooked-index.c
+++ b/gdb/dwarf2/cooked-index.c
@@ -463,10 +463,11 @@ cooked_index::start_writing_index (dwarf2_per_bfd *per_bfd)
   index_cache_store_context ctx (global_index_cache, per_bfd);
 
   /* This must be set after all the finalization tasks have been
-     started, because it may call 'wait'.  */
+     started, because it may call 'wait'.
+     TODO (c++14): The capture of ctx here can be rewritten to
+     "ctx = std::move (ctx)" once the standard is updated to c++14.  */
   m_write_future
-    = gdb::thread_pool::g_thread_pool->post_task ([this, per_bfd,
-						   ctx = std::move (ctx)] ()
+    = gdb::thread_pool::g_thread_pool->post_task ([this, per_bfd, ctx] ()
 	{
 	  maybe_write_index (per_bfd, ctx);
 	});

base-commit: 8d27b09d0877982dc2252c01a3f1d9c631b2d6eb
-- 
2.35.3