Re: [Boost-users] How to use noncopyable?

Subject: Re: [Boost-users] How to use noncopyable?
From: Yang Zhang (yanghatespam_at_[hidden])
Date: 2009-02-22 02:12:23

Steven Watanabe wrote:
> AMDG
> 
> Yang Zhang wrote:
>> Hi, I can't figure out how to properly use noncopyable.  I'm always
>> getting things like "has a non-virtual destructor" warnings.
> 
> Do you have a simple test case?

$ cat noncopyable.cc
#include <boost/noncopyable.hpp>
using namespace boost;
class C : noncopyable {};
int main() { return 0; }

$ g++ -Wall -g3 -o noncopyable noncopyable.cc -Wextra -Wconversion 
-Wpointer-arith -Wcast-qual -Wcast-align -Wwrite-strings -Winit-self 
-Wno-unused-parameter -Wparentheses -Wmissing-format-attribute 
-Wfloat-equal -Winline -Woverloaded-virtual -Wsign-promo -Wc++0x-compat 
-Wsynth -Wall -Werror -Wextra -Weffc++ -Wstrict-null-sentinel 
-Wno-old-style-cast -Woverloaded-virtual -Wsign-promo -Wformat=2 
-Winit-self -Wswitch-enum -Wunused -Wstrict-overflow -Wfloat-equal 
-Wundef -Wunsafe-loop-optimizations -Wpointer-arith -Wcast-qual 
-Wcast-align -Wwrite-strings -Wconversion -Wlogical-op 
-Wno-aggregate-return -Wno-missing-declarations 
-Wno-missing-field-initializers -Wmissing-noreturn 
-Wmissing-format-attribute -Wpacked -Wredundant-decls -Wunreachable-code 
-Winline -Winvalid-pch -Wlong-long -Wvolatile-register-var -Wstack-protector
cc1plus: warnings being treated as errors
noncopyable.cc:3: error: base class âclass 
boost::noncopyable_::noncopyableâ has a non-virtual destructor

I understand that this shouldn't be a problem as noncopyable is not 
meant to be used directly as any variable's static type, but I do 
require enabling this warning.

I currently use the following simple macro:

/** For use within a type definition. Makes the type non-copyable. */
#define NONCOPYABLE(type) \
   private: \
     type(const type&); \
     void operator=(const type&);

> 
>>   In fact,
>> compiling noncopyable_test.cpp gives me:
>>
>> <snip error message>
>>
>> Any hints?  Thanks in advance.
> 
> noncopyable_test.cpp isn't supposed to compile.  Did you read the comment?
> 
> //  This program demonstrates compiler errors resulting from trying to copy
> //  construct or copy assign a class object derived from class noncopyable.

Sorry, I did not.
-- 
Yang Zhang
http://www.mit.edu/~y_z/