g++ 4.8.* std::chrono Undeclared

Question

std::chrono ought to be supported in g++ 4.8.*. However, when I try to compile using it using g++ 4.8.3, it cannot find various declarations. I am, of course, using -std=c++11.

For example this invocation (from an autogenerated file; that's why the -std appears twice):

g++-4.8 -g -msse2 -m64 <defines> <warnings> -std=c++11 -fexceptions -std=c++11 <includes'-path> -c <source-file.cpp> -o <out-path>

Produces this error:

<source-file, line>: error: ‘std::chrono::monotonic_clock’ has not been declared

I wasn't able to find very much that wasn't immediately a compiler version or missing -std=c++11. By inference from this, I shouldn't need anything else.

Question: what's wrong, how do I fix it?

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

2

There is no std::chrono::monotonic_clock in standard C++. There is a std::chrono::steady_clock, however.

In fairness to Microsoft - and burritos everywhere - there was a monotonic_clock in the working drafts during the development of C++11 which was replaced by steady_clock.

edited May 23 '17 at 12:23

Community

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answered Nov 24 '14 at 19:17

Casey

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Technically, its existence is implementation-dependent. The code, for example, compiles in MSVC. Thanks. – geometrian Nov 24 '14 at 19:41
@imallett The standard allows implementations to put additional names in namespace `std` and nested namespaces, so there could well be a `std::chrono::i_like_burritos` in some implementation somewhere. But there is no requirement that namespace `chrono` has a member named `i_like_burritos` (or `monotonic_clock`) in C++11. (Or C++14, which is a shame because I really do like burritos.) – Casey Nov 24 '14 at 19:44
For sure. I'm just saying that `std::chrono::monotonic_clock` is a burrito. – geometrian Nov 24 '14 at 19:48

score 1 · Answer 2 · answered Nov 15 '15 at 12:25

It seems to me that you could use code like this to determine whether you're using an old library implementation (that provides monotonic_clock but not steady_clock) or a new one (that provides steady_clock but possibly not monotonic_clock).

#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20120322)
typedef std::chrono::monotonic_clock steady_clock;
#else
typedef std::chrono::steady_clock steady_clock;
#endif

The datestamp above corresponds to the libstdc++ shipped with GCC 4.7.0, according to GNU. I'd welcome any improvements or corrections to this code, for example to support libraries other than libstdc++.

g++ 4.8.* std::chrono Undeclared

2 Answers2