Re: Baby's First AldyVec/AltiVec patch

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

Ziemowit Laski <zlaski@apple.com> writes:

| On 23 Dec, 2003, at 15.06, Gabriel Dos Reis wrote:
| > The *syntax* is valid, but the semantic is fundamentally different.
| >
| > That is a red flag.
| >
| >   (1) it uses the same syntax to mean something completely different,
| >       and given that C and C++ grammars are not really context-free,
| >       I think there is more to say that a bare "the syntax is already
| >       valid".
| >
| >   (2) for the semantics, you already have an existing standard syntax
| >       for saying exactly the same thing.
| 
| Unfortunately, the "existing" syntax (by which I'm assuming you mean
| AldyVec) is not standard, whereas the syntax I'm proposing (as imperfect
| as it may be) _is_. :-(

No, I think you misunderstood.

     (type) {1, 2, 3, 4}

is a standard C99 syntax to designate a compond literal.  And if "type"
designates an  array then you get an array compound literal.  That is
standard. 

Your proposal is trying to give a well-defined syntax with a
standard semantic, a different semantic than what it means and what
people would expect it to mean. 

Furthermore, there is a proposal  considered and being actively worked
on by the C++ committee to get generalized initializers and
user-defined literals into the language and that proposal,
unsurprisingly, suggests the existing C99 syntax.  A discussion in the
C++ evolution group at the last meeting has shown that there is a
significant portion of C/C++ community out there that expects that
syntax to mean exactly that.

[...]

| > I would strongly recommand against extension experiments along that
| > line in GCC.
| 
| If this truly were an "experiment", I might be inclined to agree with
| you.
| Alas, the syntactic extensions we're discussing have existed in
| production
| compilers (including Apple's version of gcc) for at least 5 years.

Similarly, many problematic GNU extensions has been there in
production versions for long time before we kick them out. 

-- Gaby