site/dev/contrib/c++11.md - Issue 1820873002: Add note about Chromium's use of old libstdc++ to docs.

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Issue 1820873002: Add note about Chromium's use of old libstdc++ to docs. (Closed) Base URL: https://skia.googlesource.com/skia.git@master

Patch Set: Created 4 years, 9 months ago

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1 C++11 in Skia	1 C++11 in Skia

2 =============	2 =============

3	3

4 Skia uses C++11. But as a library, we are technically limited by what our	4 Skia uses C++11. But as a library, we are technically limited by what our

5 clients support and what our build bots support.	5 clients support and what our build bots support.

6	6

7 Skia may also be limited by restrictions we choose put on ourselves. This	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	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.	9 feasibility. This is about what we can use, a superset of what we may use.

10	10

11 The gist:	11 The gist:

12	12

13 - C++11 the language as supported by GCC 4.7 or later is pretty usable.	13 - C++11 the language as supported by GCC 4.7 or later is pretty usable.

14 - The C++11 standard library can generally be used, with some teething.	14 - The C++11 standard library can generally be used, with some teething.

15 - If you break a bot, that feature is not usable.	15 - If you break a bot, that feature is not usable.

16 - Local statics are not thread safe.	16 - Local statics are not thread safe.

17	17

18	18

19 Clients	19 Clients

20 -------	20 -------

21	21

22 The clients we pay most attention to are Chrome, Android, Mozilla, and a few	22 The clients we pay most attention to are Chrome, Android, Mozilla, and a few

23 internal Google projects.	23 internal Google projects.

24	24

25 Chrome builds with a recent Clang on Mac and Linux and with a recent MSVC on	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	26 Windows. These toolchains are new enough to not be the weak link to use any

27 C++11 language feature.	27 C++11 language feature. Chromium, however, builds against libstdc++4.6.4

	28 (STL and runtime) on Linux. This precludes direct use of a number of type

	29 traits.

28	30

29 Chrome intentionally disables thread-safe initialization of static variables,	31 Chrome intentionally disables thread-safe initialization of static variables,

30 so we cannot rely on that. Our bots disable this too, so keep an eye on TSAN.	32 so we cannot rely on that. Our bots disable this too, so keep an eye on TSAN.

31	33

32 Android builds with either a somewhat aged GCC or a recent Clang. They're	34 Android builds with either a somewhat aged GCC or a recent Clang. They're

33 generally not a weak link for C++11 language features. Android's C++ standard	35 generally not a weak link for C++11 language features. Android's C++ standard

34 library had historically been a pain, but seems to work fine these days.	36 library had historically been a pain, but seems to work fine these days.

35	37

36 Mozilla's current weak link is a minimum requirement of GCC 4.7. Most features	38 Mozilla's current weak link is a minimum requirement of GCC 4.7. Most features

37 marked in red on Mozilla's C++11 [feature	39 marked in red on Mozilla's C++11 [feature

38 matrix](https://developer.mozilla.org/en-US/docs/Using_CXX_in_Mozilla_code) are	40 matrix](https://developer.mozilla.org/en-US/docs/Using_CXX_in_Mozilla_code) are

39 marked that way because they arrived in GCC 4.8. Their minimum-supported Clang	41 marked that way because they arrived in GCC 4.8. Their minimum-supported Clang

40 and MSVC toolchains are pretty good, but MSVC 2013 will become the weak link soo n.	42 and MSVC toolchains are pretty good, but MSVC 2013 will become the weak link soo n.

41	43

42 Internal Google projects tend to support C++11 completely, including the	44 Internal Google projects tend to support C++11 completely, including the

43 full C++11 standard library.	45 full C++11 standard library.

44	46

45	47

46 Bots	48 Bots

47 ----	49 ----

48	50

49 Most of our bots are pretty up-to-date: the Windows bots use MSVC 2013, the Mac	51 Most of our bots are pretty up-to-date: the Windows bots use MSVC 2013, the Mac

50 bots a recent Clang, and the Linux bots GCC 4.8 or a recent Clang. Our Android	52 bots a recent Clang, and the Linux bots GCC 4.8 or a recent Clang. Our Android

51 bots use a recent toolchain from Android (see above), and our Chrome bots use	53 bots use a recent toolchain from Android (see above), and our Chrome bots use

52 Chrome's toolchains (see above). I'm not exactly sure what our Chrome OS bots	54 Chrome's toolchains (see above). I'm not exactly sure what our Chrome OS bots

53 are using. They're probably our weak link right now, though problems are rare.	55 are using. They're probably our weak link right now, though problems are rare.

54	56

55 I believe our bots' ability to use C++11 matches Mozilla's list nearly identical ly.	57 I believe our bots' ability to use C++11 matches Mozilla's list nearly identical ly.

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