1 C++11 in Skia 2 ============= 3 4 Skia is exploring the use of C++11. As a library, we are technically limited 5 by what our clients support and what our build bots support. 6 7 Skia may also be limited by restrictions we choose put on ourselves. This 8 document is not concerned with C++11 policy in Skia, only its technical 9 feasibility. This is about what we can use, a superset of what we may use. 10 11 The gist: 12 13 - C++11 the language as supported by GCC 4.4 or later is probably usable. 14 - If you break a bot, that feature is not usable. 15 - The C++11 standard library can't generally be used. 16 - Local statics are not thread safe. 17 18 19 Clients 20 ------- 21 22 The clients we pay most attention to are Chrome, Android, Mozilla, and a few 23 internal Google projects. 24 25 Chrome builds with a recent Clang on Mac and Linux and with a recent MSVC on 26 Windows. These toolchains are new enough to not be the weak link to use any 27 C++11 language feature. But Chrome still supports Mac OS X 10.6, which does 28 not ship with a C++11 standard library. So [Chrome has banned the use of the 29 C++11 standard library](http://chromium-cpp.appspot.com/). Some header-only 30 features are probably technically fine, but the Mac toolchain will prevent us 31 from even trying at compile time as long as we target 10.6 as our minimum API 32 level. 33 34 Chrome intentionally disables thread-safe initialization of static variables, 35 and MSVC doesn't support it at all, so we cannot rely on that. 36 37 Android builds with either a recent GCC or a recent Clang. They're generally 38 not a weak link for C++11 language features. Android's C++ standard library 39 has always been a pain, but since we can't use it anyway (see Chrome), don't 40 worry about it. 41 42 Mozilla's current weak link is a minimum requirement of GCC 4.6. Most features 43 marked in red on Mozilla's C++11 [feature 44 matrix](https://developer.mozilla.org/en-US/docs/Using_CXX_in_Mozilla_code) are 45 marked that way because they arrived in GCC 4.7 or GCC 4.8. Their 46 minimum-supported Clang and MSVC toolchains are great. They also appear to ban 47 the C++ standard library. 48 49 Internal Google projects tend to support C++11 completely, including the 50 full C++11 standard library. 51 52 53 Bots 54 ---- 55 56 Most of our bots are pretty up-to-date: the Windows bots use MSVC 2013, the Mac 57 bots a recent Clang, and the Linux bots GCC 4.8 or a recent Clang. Our Android 58 bots use a recent toolchain from Android (see above), and our Chrome bots use 59 Chrome's toolchains (see above). I'm not exactly sure what our Chrome OS bots 60 are using, but they've never been a problem. 61 62 A few miscellaneous compile-only bots are actually our current overall weak link: 63 64 - Our iOS builds are driven from a Mac 10.7 machine using some unknown old Clang. 65 Who knows how old that is or what it supports? It's probably due for an update. 66 67 If we were to eliminate the problems of iOS bots, our ability to 68 use C++11 would match Mozilla's list nearly identically. 69
