Blocks in C, not C++ [LWN.net]

Blocks in C, not C++

Posted Sep 16, 2009 19:03 UTC (Wed) by ncm (guest, #165)
Parent article: Tornado and Grand Central Dispatch: a quick look

The article doesn't mention that Apple has the "blocks" feature for their new non-Gcc C compiler, Clang, but not for C++. We may guess that as the GNU C++ compiler, G++, incorporates features planned for C++0xA, the new C++ "lambda" feature will be used at the library level to implement the same facilities as had to be built into the core compiler for C.

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Blocks in C, not C++

Posted Sep 16, 2009 19:15 UTC (Wed) by ncm (guest, #165) [Link] (7 responses)

I should clarify that "C++0xA" is a cheeky informal name for the next ISO Standard C++ language, due out soon. It had been labeled "C++0x" on the expectation that that would become "C++09" after release this year. "0xA" is the C++ (and C) hexadecimal notation for the decimal value 10. The name "C++0xA", then, implies the pessimistic expectation that it is delayed to 2010. To me the opportunity to call it C++0xA is reason enough to delay its release.

Blocks in C, not C++

Posted Sep 16, 2009 19:25 UTC (Wed) by cry_regarder (subscriber, #50545) [Link] (6 responses)

In which case it would be C++0A, not C++0xA.

Cry

Blocks in C, not C++

Posted Sep 16, 2009 21:36 UTC (Wed) by elanthis (guest, #6227) [Link] (5 responses)

It'll probably be C++1x (e.g. C++10, C++11, whatever). There has been no formal decision to go with hexadecimal numbering that I'm aware of. Informal discussions between committee members have been pretty mixed between continuing with a C++0x moniker or using C++1x.

Blocks in C, not C++

Posted Sep 16, 2009 22:39 UTC (Wed) by ncm (guest, #165) [Link] (4 responses)

"C++98" was never a formal name. The formal name is "ISO 14882:1998". Whether "C++10" or "C++0xA" wins out (or, indeed, C++0xB) is purely a matter of popular usage. You (and you, and you!) can help swing it the way you want.

Blocks in C, not C++

Posted Sep 17, 2009 17:17 UTC (Thu) by cry_regarder (subscriber, #50545) [Link] (3 responses)

> Whether "C++10" or "C++0xA" wins out (or, indeed, C++0xB) is

\begin{pedantic}
NOT "C++0xA". The "x" is a wild card which under normal expectations would be replaced with an element of [0-9]. The joke is that since "C++0x" is taking so long. We (they) will keep the implied promise of a first decade delivery by extending the membership of the wildcard to [0-F] (hex).

That means that if you replace the "x" with an "A", you write it as "C++0A" not as "C++0xA"!.

In any case (as pointed out elsewhere), the name is not the real name for the language. It is a joke. The "official" non-real name will surely be of the form "C++1x".
\end{pedantic}

Cry

next C++ standard

Posted Sep 17, 2009 19:17 UTC (Thu) by man_ls (guest, #15091) [Link] (2 responses)

I think that the joke is funnier if you interpret the "0x" as the hexadecimal prefix in C and, well, C++; so "0xA" is "10" in legal C. Therefore decimal "C++09" is followed by hexadecimal "C++0xA".

next C++ standard

Posted Sep 18, 2009 11:41 UTC (Fri) by liljencrantz (guest, #28458) [Link] (1 responses)

But 0 as a prefix means octal, so 09 is actually an illegal constant. :-(

next C++ standard

Posted Sep 27, 2009 22:23 UTC (Sun) by bluss (guest, #47454) [Link]

Well then, fools were we to expect that an illegal C++09 would ever be released!

Blocks in C, not C++

Posted Sep 16, 2009 20:45 UTC (Wed) by atai (subscriber, #10977) [Link] (8 responses)

Is there any plan to implement similar feature (extension) in gcc?

Blocks in C, not C++

Posted Sep 16, 2009 20:51 UTC (Wed) by nteon (guest, #53899) [Link]

recent llvm-gcc (available on Debian and other fine platforms) should have
blocks support built-in I believe. Clang as well. To actually _use_ blocks,
you need the BlocksRuntime shared library, available as part of compiler-rt [1]
(which builds and runs on Linux as of last week). Unfortunately I don't think
its packaged anywhere yet.

1 - http://compiler-rt.llvm.org

Blocks in C, not C++

Posted Sep 16, 2009 20:54 UTC (Wed) by drag (guest, #31333) [Link] (1 responses)

It would be what is required if you want GCD support for C++, I suppose.

Clang/LLVM does not support anything but C. For C++ you'd need GCC proper or GCC/LLVM. I beleive.

Blocks in C, not C++

Posted Sep 17, 2009 2:12 UTC (Thu) by jdahlin (subscriber, #14990) [Link]

It supports both ObjC and C++, it may not support the standard as well as
GCC, but enough to compile a couple of small test programs. I'm confident
clang will deliver a C++ compiler reasonably compatible with GCC sometime
next year.

Blocks in C, not C++

Posted Sep 16, 2009 21:54 UTC (Wed) by ncm (guest, #165) [Link] (4 responses)

If you're asking whether this "blocks" feature will be added to the Gcc C compiler, I would expect not until it gets very close to standardization as an ISO C feature. I don't know if Apple has placed this blocks thing before the C committee yet, or what the C committee thinks/would think of it. The GNU Gcc developers are very keen on observing relevant standards; proprietary features encourage lock-in. I doubt anybody would bother putting it in before that, given that the Clang C compiler has it.

Blocks in C, not C++

Posted Sep 16, 2009 22:46 UTC (Wed) by ncm (guest, #165) [Link] (1 responses)

I will note further that the Lambda feature in C++ has different syntax from Blocks, and there will be strong pressure, particularly from implementers, on the C committee to match the C++ Lambda syntax, i.e. using "[]" where Apple's Blocks uses "^". (Ironically, "[]" looks typographically more like a block, and "^" looks more like a lambda.) I expect Apple to support both syntaxes in the end.

Blocks in C, not C++

Posted Sep 17, 2009 1:29 UTC (Thu) by busterb (subscriber, #560) [Link]

But [] is used by objective C to call methods, so Apple is likely to not support this, at least not OS
X's most-supported language.

Blocks in C, not C++

Posted Sep 18, 2009 8:01 UTC (Fri) by marcH (subscriber, #57642) [Link] (1 responses)

> The GNU Gcc developers are very keen on observing relevant standards; proprietary features encourage lock-in.

Here is a list of non-standard GCC extensions:

http://www.ibm.com/developerworks/linux/library/l-gcc-hacks/

You can probably find a better list; this one took me only 15 seconds to find.

Blocks in C, not C++

Posted Sep 19, 2009 3:22 UTC (Sat) by wahern (subscriber, #37304) [Link]

Just read the GCC documentation:

http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/C-Extensions....