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Re: Proposal for automatic generation of c++ header files
On 14 January 2011 17:10, Achilleas Margaritis wrote:
>>> There is a solution to that: the compiler, knowing that foo::bar is
>>> not an inline function, it does not inline the function but it
>>> automatically compiles the relevant symbol in the foo.o object file.
>>
>> Which is a change to the language semantics!
>
> The compiler can inline the trivial member functions and leave the
> rest as is. Although technically it is a change in language semantics,
> it's a very minor change, that I doubt will have anyone worried.
Except compiler and linker writers.
And those are the people you're asking to implement your idea, without
a proper spec or convincing arguments.
> Look at the benefit of not having to create headers though...for me,
> it's a good trade off.
>
>> A change to how the compiler processes the source code is a change to
>> the language. ?The rules on template instantiation, inline functions,
>> symbol visibility, inline namespaces etc. would probably all be
>> affected.
>
> I do not see how anything else other than inlining is to be affected.
>
> Care to show an example?
No, the onus would be on you to demonstrate your change doesn't affect
such things.
I like the status quo, and am confident that doesn't require change to
the language.
If you don't like the status quo and claim your alternative doesn't
change things, you need to demonstrate that.
>>
>> You also don't seem to have considered header dependencies. ?If
>> foo.cpp #includes ten files, some of which are needed for the
>> interface and some for the implementation, how many of them should be
>> copied to foo.hpp by your "simple" copy'n'paste? ?Should the compiler
>> analyse which headers are needed just for the interface declarations,
>> and only include those headers? ?Or auto-generate forward-declarations
>> of all the needed entities?
>> Or just include all of them, even though some headers may only be
>> needed for the implementations, resulting in namespace pollution in
>> other translation units and possible ambiguities, conflicts, or
>> dependency cycles?
>
> All of them.
>
> I'll take automatic generation of headers + increased compilation
> times any day over manual generation of headers. New computers and
> hard disks can always be purchased and are much cheaper than people.
>
> If I encountered a problem with dependency cycles, then I would use
> the old way of manually writing headers, which will still be
> available.
OK, fair enough.