Re: [PATCH] fix compile error with clang

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

On 2018-12-20 4:38 p.m., Dave Murphy wrote:
> Hi Simon,
> 
> The error I get is
> 
> ../../binutils-gdb/gdb/unittests/observable-selftests.c:73:31: error:
> default initialization of an object of const type 'const
> gdb::observers::token' without a user-provided default constructor
>   const gdb::observers::token token1, token2, token3;
>                               ^
>                                     {}
> clang version is
> 
> davem@devkit-builder:~$ /opt/osx/bin/x86_64-apple-darwin15-clang --version
> 
> clang version 3.8.1-24 (tags/RELEASE_381/final)
> Target: x86_64-apple-darwin15
> Thread model: posix
> 
> (targeting 10.9+ host)
> 
> build machine is debian stretch
> 
> davem@devkit-builder:~$ uname -a
> Linux devkit-builder 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2
> (2018-10-27) x86_64 GNU/Linux

Thanks for the details, I was able to reproduce using clang 3.8 on Debian stable.
I think it's worth fixing since it doesn't hurt when building other compilers,
and clang 3.8 is still the default clang version on the current Debian stable.

Here's what I pushed:

From 3dcfdc58656caa4a38e1fde73a07a19114347226 Mon Sep 17 00:00:00 2001
From: Dave Murphy <davem@devkitpro.org>
Date: Fri, 21 Dec 2018 11:14:28 -0500
Subject: [PATCH] Fix compile error with clang 3.8

When compiling with clang 3.8 (default clang version on Debian
Stretch, the current stable), we get errors like this:

  CXX    dtrace-probe.o
../../binutils-gdb/gdb/dtrace-probe.c:103:31: error: default initialization of an object of const type 'const dtrace_static_probe_ops' without a user-provided default constructor
const dtrace_static_probe_ops dtrace_static_probe_ops;
                              ^

Silence them by value-initializing those objects.  It's not necessary
with other compilers (later clang versions, gcc), but it shouldn't
hurt either.
---
 gdb/ChangeLog                        | 10 ++++++++++
 gdb/dtrace-probe.c                   |  2 +-
 gdb/probe.c                          |  2 +-
 gdb/record-btrace.c                  |  2 +-
 gdb/stap-probe.c                     |  2 +-
 gdb/tui/tui-hooks.c                  |  2 +-
 gdb/unittests/observable-selftests.c |  2 +-
 7 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 28ab3345032..953bc17be1f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,13 @@
+2018-12-21  Dave Murphy  <davem@devkitpro.org>
+
+	* dtrace-probe.c (dtrace_static_probe_ops): Explicit zero
+	initialise.
+	* probe.c (any_static_probe_ops): Ditto.
+	* record-btrace.c (record_btrace_thread_observer_token): Ditto.
+	* stap-probe.c (stap_static_probe_ops): Ditto.
+	* tui/tui-hooks.c (tui_observers_token): Ditto.
+	* unittests/observable-selftests.c (token1, token2, token3): Ditto.
+
 2018-12-19  Andrew Burgess  <andrew.burgess@embecosm.com>

 	* gdb/dummy-frame.c (default_dummy_id): Defined new function.
diff --git a/gdb/dtrace-probe.c b/gdb/dtrace-probe.c
index fa4e06e7947..0c75904c585 100644
--- a/gdb/dtrace-probe.c
+++ b/gdb/dtrace-probe.c
@@ -100,7 +100,7 @@ public:

 /* DTrace static_probe_ops.  */

-const dtrace_static_probe_ops dtrace_static_probe_ops;
+const dtrace_static_probe_ops dtrace_static_probe_ops {};

 /* The following structure represents a dtrace probe.  */

diff --git a/gdb/probe.c b/gdb/probe.c
index 1f3da213efc..5702afe0d2f 100644
--- a/gdb/probe.c
+++ b/gdb/probe.c
@@ -60,7 +60,7 @@ public:

 /* Static operations associated with a generic probe.  */

-const any_static_probe_ops any_static_probe_ops;
+const any_static_probe_ops any_static_probe_ops {};

 /* A helper for parse_probes that decodes a probe specification in
    SEARCH_PSPACE.  It appends matching SALs to RESULT.  */
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index 1ca0176ec81..92c0821ec92 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -143,7 +143,7 @@ static record_btrace_target record_btrace_ops;

 /* Token associated with a new-thread observer enabling branch tracing
    for the new thread.  */
-static const gdb::observers::token record_btrace_thread_observer_token;
+static const gdb::observers::token record_btrace_thread_observer_token {};

 /* Memory access types used in set/show record btrace replay-memory-access.  */
 static const char replay_memory_access_read_only[] = "read-only";
diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
index ed7e1a0d3fb..b79cb153a93 100644
--- a/gdb/stap-probe.c
+++ b/gdb/stap-probe.c
@@ -119,7 +119,7 @@ public:

 /* SystemTap static_probe_ops.  */

-const stap_static_probe_ops stap_static_probe_ops;
+const stap_static_probe_ops stap_static_probe_ops {};

 class stap_probe : public probe
 {
diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index efa02e2f08a..3a9bff30a6a 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -205,7 +205,7 @@ tui_normal_stop (struct bpstats *bs, int print_frame)

 /* Token associated with observers registered while TUI hooks are
    installed.  */
-static const gdb::observers::token tui_observers_token;
+static const gdb::observers::token tui_observers_token {};

 /* Attach or detach a single observer, according to ATTACH.  */

diff --git a/gdb/unittests/observable-selftests.c b/gdb/unittests/observable-selftests.c
index 6f2f7e8bccf..903baa741c5 100644
--- a/gdb/unittests/observable-selftests.c
+++ b/gdb/unittests/observable-selftests.c
@@ -70,7 +70,7 @@ run_tests ()
      attached.  */
   notify_check_counters (0, 0, 0);

-  const gdb::observers::token token1, token2, token3;
+  const gdb::observers::token token1 {}, token2 {} , token3 {};

   /* Now, attach one observer, and send a notification.  */
   test_notification.attach (&test_second_notification_function, token2);
-- 
2.20.1