std::round is not a member of std on android

Question

I am using std::round from C++ 11 on a Qt app built for android & iOS. But on android, I get the error that std::round is not a member of std in spite of including the cmath header.

How can I make std::round work on android ? Is there an alternative to std::round ?

Following is my android environment:

ANDROID_NDK_PLATFORM = android-23
NDK version          = r13b
ANDROID_NDK_TOOLCHAIN_VERSION = 4.9

@DanAlbert Is there an upcoming release of NDK where these issues will be resolved ? — TheWaterProgrammer, Feb 26 '17 at 19:07
As the bug says, it's scheduled for r15. In case tl;dr, it should be noted that this will never be fixed for gnustl, and will actually be "fixed" by making libc++ reliable enough that there will be no reason to use gnustl. — Dan Albert, Feb 27 '17 at 21:17

score 2 · Accepted Answer · edited May 23 '17 at 12:18

2

Looks like a few functions from the cmath header are missing from the Android-NDK, see here for more details.

It's very easy to implement your own round function however:

template<typename T>
T round(T v) {
  return int(v + 0.5);
}

Or check other suggestions/implementations here.

edited May 23 '17 at 12:18

Community

1
1

answered Feb 25 '17 at 19:14

101010

41,839
11
94
168

1

`int(v + 0.5);` fails for many cases. OK for learner code, yet not production code. – chux - Reinstate Monica Jul 12 '18 at 15:26

Bruno Alexandre Rosa · Answer 2 · 2018-11-06T15:12:54.527

1

How can I make std::round work on android ?

(EDIT: updated instructions)

Switch to NDK r18 and remove the ANDROID_NDK_TOOLCHAIN_VERSION = 4.9 line since gcc is now completely removed from NDK, defaulting to clang.

edited Nov 06 '18 at 15:12

answered Sep 28 '17 at 13:37

Bruno Alexandre Rosa

550
6
20

std::round is not a member of std on android

2 Answers2

Linked