Re: [boost] [Review:Contract] Andrzej's review

Subject: Re: [boost] [Review:Contract] Andrzej's review
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-09-06 14:03:23

AMDG

On 09/06/2012 09:50 AM, Lorenzo Caminiti wrote:
> 
> I was thinking more on how to support compiler-specific declaration
> extensions. Supposedly, the lib will not do anything with these but to
> repeat them verbatim when the macros expand the underlining C++ code
> (because these extensions do not affect Contract Programming).
> Therefore, I was thinking that I could support a generic verbatim(...)
> identifier that can appear anywhere within the declarations and will
> specify tokens that the lib will simply repeat "as is" in the actual
> C++ declarations of the expanded macros. For example:
> 
> CONTRACT_CLASS(
>     verbatim(__declspec(dllimport)) class (x)
> ) {
>     CONTRACT_CLASS_INVARIANT( void )
> } varx;
> 
> CONTRACT_CLASS(
>     class verbatim(__declspec(dllimport)) (x)
> ) {
>     CONTRACT_CLASS_INVARIANT( void )
> };
> 
> If possible, this could be used to support a number of different
> (all?) compiler extensions because the lib doesn't need to know
> anything about the content of a verbatim clasule but just that the
> specified tokens have to be repeated "in place and as they are" when
> expanding the macros.
> 

One difficulty with this is defining
exactly what "in place" means.  You'll
need to specify how locations in your
syntax map to locations in the C++
declaration in all the places where
the syntax is different.  e.g.

void (f)(int i, verbatim(extension) default 10)

a) void f(int i extension = 1)
b) void f(int i = extension 1)
c) This is illegal

> In contrast if I implement the code below, it will only work for
> __declspec and not for other extensions (because the lib needs to be
> aware of __declspec and not just of verbatim here):
> 
> CONTRACT_CLASS(
>     __declspec(dllimport) class (x)
> ) {
>     CONTRACT_CLASS_INVARIANT( void )
> } varx;
> 
> CONTRACT_CLASS(
>     class __declspec(dllimport) (x)
> ) {
>     CONTRACT_CLASS_INVARIANT( void )
> };
> 
> What do you think?
> 

I think both are good.  You should implement
important known compiler extensions like
__declspec and __attribute__ directly and
also provide verbatim to handle unknown
or future compiler extensions.

In Christ,
Steven Watanabe