Re: [PATCH] Add macro DISABLE_COPY_AND_ASSIGN

[Yao Qi <qiyaoltc at gmail dot com>]

On Sat, Sep 9, 2017 at 1:27 PM, Ian Lance Taylor <iant@golang.org> wrote:
>
> The patch to include/ansidecl.h is basically OK.  Please add an
> example in the comment showing how to use it: after `private:`, and
> with a trailing semicolon.  Thanks.

Patch below is committed.  Thanks for the review.

>
> The patches to the other files will have to be approved by the
> relevant maintainers.
>

I'll split it and post them later.

-- 
Yao (齐尧)

From 753d12319d85876c2513029037af539c43717251 Mon Sep 17 00:00:00 2001
From: qiyao <qiyao@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri, 15 Sep 2017 15:40:50 +0000
Subject: [PATCH] [include] Add macro DISABLE_COPY_AND_ASSIGN

We have many classes that copy cotr and assignment operator are deleted
in different projects, gcc, gdb and gold.  So this patch adds a macro
to do this, and replace these existing mechanical code with macro
DISABLE_COPY_AND_ASSIGN.

The patch was posted in gdb-patches,
https://sourceware.org/ml/gdb-patches/2017-07/msg00254.html but we
think it is better to put this macro in include/ansidecl.h so that
other projects can use it too.

include:

2017-09-15  Yao Qi  <yao.qi@linaro.org>
	    Pedro Alves  <palves@redhat.com>

	* ansidecl.h (DISABLE_COPY_AND_ASSIGN): New macro.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@252823 138bc75d-0d04-0410-961f-82ee72b054a4
---
 include/ChangeLog  |  5 +++++
 include/ansidecl.h | 26 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/ChangeLog b/include/ChangeLog
index 4703588..0221586 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-15  Yao Qi  <yao.qi@linaro.org>
+	    Pedro Alves  <palves@redhat.com>
+
+	* ansidecl.h (DISABLE_COPY_AND_ASSIGN): New macro.
+
 2017-09-12  Jiong Wang  <jiong.wang@arm.com>
 
 	* dwarf2.def (DW_CFA_AARCH64_negate_ra_state): New DW_CFA_DUP.
diff --git a/include/ansidecl.h b/include/ansidecl.h
index ab3b895..450ce35 100644
--- a/include/ansidecl.h
+++ b/include/ansidecl.h
@@ -360,6 +360,32 @@ So instead we use the macro below and test it against specific values.  */
 # define FINAL
 #endif
 
+/* A macro to disable the copy constructor and assignment operator.
+   When building with C++11 and above, the methods are explicitly
+   deleted, causing a compile-time error if something tries to copy.
+   For C++03, this just declares the methods, causing a link-time
+   error if the methods end up called (assuming you don't
+   define them).  For C++03, for best results, place the macro
+   under the private: access specifier, like this,
+
+   class name_lookup
+   {
+     private:
+       DISABLE_COPY_AND_ASSIGN (name_lookup);
+   };
+
+   so that most attempts at copy are caught at compile-time.  */
+
+#if __cplusplus >= 201103
+#define DISABLE_COPY_AND_ASSIGN(TYPE)		\
+  TYPE (const TYPE&) = delete;			\
+  void operator= (const TYPE &) = delete
+  #else
+#define DISABLE_COPY_AND_ASSIGN(TYPE)		\
+  TYPE (const TYPE&);				\
+  void operator= (const TYPE &)
+#endif /* __cplusplus >= 201103 */
+
 #ifdef __cplusplus
 }
 #endif
-- 
1.9.1