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

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

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On 8/8/23 00:16, Tom Tromey wrote:
> Simon> When we encounter things like this, should we add some greppable
> Simon> TODO comment to record an actionable item for when we switch to a
> Simon> more recent C++ version?
> 
> FWIW I know of one other instance of this, in gdb_demangle:
> 
> 	  std::string copy = name;
> 	  run_on_main_thread ([=] ()
> 	    {
> 	      report_failed_demangle (copy.c_str (), core_dump_allowed,
> 
> Here, the name is copied twice, but with move captures there could be
> just a single copy.

Like so?

Thanks,
- Tom



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From 7a6f3e7e39701b2b0e2f3b8f761e7c32f46af4a6 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Tue, 8 Aug 2023 01:34:45 +0200
Subject: [PATCH] [gdb/build] Use move capture in gdb_demangle

Use move capture in gdb_demangle when compiling for c++14 or higher, to save a
std::string copy.

Tested on x86_64-linux.

Reported-By: Tom Tromey <tom@tromey.com>
---
 gdb/cp-support.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index 2fb9d9ef0b2..0300727434d 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -1656,7 +1656,13 @@ gdb_demangle (const char *name, int options)
 	     we might be in a background thread.  Instead, arrange for
 	     the reporting to happen on the main thread.  */
 	  std::string copy = name;
-	  run_on_main_thread ([=] ()
+	  run_on_main_thread ([
+#if __cplusplus >= 201402L
+			       =, copy = std::move (copy)
+#else
+			       =
+#endif
+			       ] ()
 	    {
 	      report_failed_demangle (copy.c_str (), core_dump_allowed,
 				      crash_signal);

base-commit: ddbe8c3c8a8665e77f9ebb108c5627a6ebecb81f
-- 
2.35.3