C89 vs. C99

2016-11-12 11:57 GMT+01:00 Nikita Popov <nikita.ppv@gmail.com>:

I use VC11, which is the compiler used for 5.6 builds, technically its on our list to drop support for in 7.2+ I think was the plan, while Anatol uses VC14+ mainly, which is the compiler used for 7.0+ builds. So technically I shouldn't really be using VC11 for 7.0+, but on my current small setup, I have only configured VC11, but I plan on fully upgrading to VC14 only soon, as 5.6 does not have much active development that cannot be done on VC14. According to Wikipedia: Visual C++ 2012 and earlier did not support C99. Visual C++ 2013 implements a limited subset of C99 required to compile popular open-source projects. Visual C++ 2015 implements the C99 standard library, with the exception of any library features that depend on compiler features not yet supported by the compiler (for example, <tgmath.h> is not implemented). And ofcourse the version mapping: VC11 - Visual C++ 2012 VC12 - Visual C++ 2013 VC14 - Visual C++ 2015 So as long as future developments are compatible with VC14, its fine with me

On Sat, 12 Nov 2016, Nikita Popov wrote:

I would want to write down in our coding guidelines that we should *NOT* do declarations after code, as you will no longer have an overview of all the types in one place anymore. cheers, Derick

Hi Nikita,

That's a good spot. Indeed, VC++14 implements the C99 features in big extent, as announced here https://msdn.microsoft.com/en-us/library/hh409293.aspx#BK_CRT VC++11 is only usable with 7.x, because there was no case yet, forcing to use a compiler feature that would require VC++14 only. Once this moment came, VC11 is out with fire. I use VC11 only for PHP-5.6, as that's what we stick to for the standard builds. A less extensive C99 support was already present in VC++12. We produce the standard 7.x builds with VC++14, not only for PHP but also for the dependency libraries and PECL. Practically, VC++14 is already used for over a year, started even with a pre release version, and it only shows good results. With C libraries, there was several issues, but they all was solvable in favor of VC14. Otherwise, while the old code feels fine with the newer compiler, the new horizons open themselves. It was already possible, to get some extensions to support Windows build for 7.0 for this exact reason. Either because the devs didn't care about C89 anymore (fe ext/amqp) or because the dependency library expected a C99 compiler (fe librdkafka). In many cases, I haven't checked the exact C99 features libraries use, but just went to compile them with VC++14, and there was almost no disappointment. Well, it could be, but it's then not related to C99 anymore, but more is about some unportable platform features. Thus, based on my current experiences now over one year, I can tell that in regard to VS and C99 features it looks quite optimistic. We de facto use C99 compilers nowadays, and we have several cases in the core that would profit from this. I can at least recall some cases in math functions, but there should be more not necessarily related to the C99 specific syntax changes. Regarding the syntax caveats - well, the code esthetics is something that we need to agree on. As for me, some cases using inline declarations are still useful, fe "for (int k = 0, ....);" where the scope is guaranteed to be local to the loop. Or the case to partially initialize some struct members. Indeed, enabling C99 would mean, the course should be in first place to accept the features. We can then extend our coding style to make the specific project preferences clear. But in general, there is much more than just mixing code and declarations or any other syntactic sugar. Take for example the bool and other new datatypes, array to pointer conversion, variable lenth arrays, comments with // and other even more intrusive features. At some point, one might not recognize the PHP source how we know it today, once C99 is indeed used in full extent :) C99 indeed is full of other features, but the coding style agreement is indeed the only way to solve the esthetic issues. And the less we would exclude with the coding style - the easier it would be to contribute. IMHO, if we decide to move to C99, we should do it the strict way, unlike we do now with C89. VC++ enables C99 the way it can't be turned off, but some parts are still missing. In case of GCC and other compilers, the -std=c99 should be enforced. A quick check shows, at least gcc 4.9.2 with -std=c99 fails to compile PHP. Currently, while holding on C89 in general, compilers provide a mess of things like partial availability of headers, datatype definitions, etc. If we don't do it a strict way, we risk to have even more inconsistent source codes following the standard only partially. VC still lacks on some features, I'm not sure how strict/complete the C99 implementation in GCC/Clang is. Of course, after all, there will be still some compiler dependent difference. But in general - enforcing the switch will at least ensure the required standard is provided. Probably, if the work on this should be started, it'd be good to do it soon so we're in time with 7.2. For the Windows side - there's currently an effort of a new binary tools implementation https://github.com/OSTC/php-sdk-binary-tools/tree/new_binary_tools It aims to support newer tools and better operation, but also there's no plan to support the environments for compilers older than VC14. If everything goes well, and that's actually the plan, the SDK will replace the old one for the standard builds. It could be, and actually would make sense, to require the new SDK for 7.2, which will automatically make VC11 unsupported for it. This would comply well, if a decision to require a C99 compiler for the whole project were taken. If we do that, we'd better get started soon, so we have enough time for fixes and QA, and so the new coding style guide lines can be worked out and agreed. And so we have enough time to turn back, if there are unsolvable issues. Regards Anatol

Morning,

Not sure if serious ... but I will harass you to change code that is mixi [1]. I think actually disallowing mixing lends some readability and uniformity to the code in php-src, that I would hate to see disappear ... Cheers Joe [1] https://en.wikipedia.org/wiki/Myxomatosis? On Sat, Nov 12, 2016 at 11:27 AM, Christoph M. Becker <cmbecker69@gmx.de> wrote:

On Sat, Nov 12, 2016 at 4:27 AM, Christoph M. Becker <cmbecker69@gmx.de> wrote:

Last time this came up some of us started putting together test cases for people to check compilers with. See https://github.com/FriendsOfPHP/phpnextctest If you have access to any of these compilers we care about please test. If you would like to see more kinds of tests please add them.

On 11/12/2016 06:27 AM, Christoph M. Becker wrote:

Oracle Studio compiler tools are fully compliant with C99 and has been for a very very long time. I would also note that php7.x does not compile out of the box, yet. However I am looking into why. Dennis Clarke