Re: [PATCH] Replace gdb_static_assert with static_assert

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

On 2017-12-05 11:32 AM, Simon Marchi wrote:
> On 2017-12-05 11:29, Yao Qi wrote:
>> Simon Marchi <simon.marchi@ericsson.com> writes:
>>
>>> gdb/ChangeLog:
>>>
>>>     * common/gdb_assert.h: Remove.
>>
>>         * common/gdb_assert.h (gdb_static_assert): Remove.
>>
>> because you don't remove this file.
> 
> Woops, thanks.
> 
>>> -/* A static assertion.  This will cause a compile-time error if EXPR,
>>> -   which must be a compile-time constant, is false.  */
>>> -
>>> -#define gdb_static_assert(expr) \
>>> -  extern int never_defined_just_used_for_checking[(expr) ? 1 : -1]
>>
>> Did you consider define gdb_static_assert as static_assert ((expr), "")?
>> You don't have to change anywhere else.  Additionally, one day we move
>> to c++17, we can replace gdb_static_assert with static_assert globally.
> 
> That's a good idea, I'll do that.
> 
> Thanks,
> 
> Simon

Here's what I pushed.  Thanks again for the suggestion.

Simon

From ed9376bd95c52ba00aa37b224b4407030a00d184 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@ericsson.com>
Date: Tue, 5 Dec 2017 16:15:08 -0500
Subject: [PATCH] Redefine gdb_static_assert as static_assert

Since we use C++11, we can use static_assert instead doing the trick
that makes a negative-sized array if the expression is false.
static_assert is built in the language and gives clearer error messages.

To avoid modifying the usages of gdb_static_assert, redefine
gdb_static_assert in terms of static_assert, passing an empty message.
If we want to add an assert with a message, it's always possible to use
static_assert directly.

gdb/ChangeLog:

	* common/gdb_assert.h (gdb_static_assert): Redefine using
	static_assert.
---
 gdb/ChangeLog           | 5 +++++
 gdb/common/gdb_assert.h | 3 +--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 524eef3..ef0c4bd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2017-12-05  Simon Marchi  <simon.marchi@ericsson.com>

+	* common/gdb_assert.h (gdb_static_assert): Redefine using
+	static_assert.
+
+2017-12-05  Simon Marchi  <simon.marchi@ericsson.com>
+
 	* ada-lang.c (ada_collect_symbol_completion_matches): Remove
 	unused variables.
 	(ada_is_redundant_range_encoding): Likewise.
diff --git a/gdb/common/gdb_assert.h b/gdb/common/gdb_assert.h
index 5de9d3f..20825c8 100644
--- a/gdb/common/gdb_assert.h
+++ b/gdb/common/gdb_assert.h
@@ -22,8 +22,7 @@
 /* A static assertion.  This will cause a compile-time error if EXPR,
    which must be a compile-time constant, is false.  */

-#define gdb_static_assert(expr) \
-  extern int never_defined_just_used_for_checking[(expr) ? 1 : -1]
+#define gdb_static_assert(expr) static_assert (expr, "")

 /* PRAGMATICS: "gdb_assert.h":gdb_assert() is a lower case (rather
    than upper case) macro since that provides the closest fit to the
-- 
2.7.4