luo980/stduuid
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

note about mingw

Browse Source
This commit is contained in:
Marius Bancila 2021-12-22 23:43:35 +02:00
parent 9857cd372a
commit c6ad65304b
1 changed files with 6 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
README.md
View File

@ -256,11 +256,17 @@ The following is a list of examples for using the library:
auto h2 = std::hash<uuid>{}; auto h2 = std::hash<uuid>{};
assert(h1(str) == h2(id)); assert(h1(str) == h2(id));
``` ```
### Random uuids
If you generate uuids using the `basic_uuid_random_generator` and [std::random_device](https://en.cppreference.com/w/cpp/numeric/random/random_device) to seed a generator, keep in mind that this might not be non-deterministic and actually generate the same sequence of numbers: If you generate uuids using the `basic_uuid_random_generator` and [std::random_device](https://en.cppreference.com/w/cpp/numeric/random/random_device) to seed a generator, keep in mind that this might not be non-deterministic and actually generate the same sequence of numbers:
> std::random_device may be implemented in terms of an implementation-defined pseudo-random number engine if a non-deterministic source (e.g. a hardware device) is not available to the implementation. In this case each std::random_device object may generate the same number sequence. > std::random_device may be implemented in terms of an implementation-defined pseudo-random number engine if a non-deterministic source (e.g. a hardware device) is not available to the implementation. In this case each std::random_device object may generate the same number sequence.
This could be a problem with MinGW. See [Bug 85494 - implementation of random_device on mingw is useless](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85494). This was fixed in GCC 9.2.
A portable alternative is to use the [Boost.Random](https://www.boost.org/doc/libs/1_78_0/doc/html/boost_random.html) library.
## Support ## Support
The library is supported on all major operating systems: Windows, Linux and Mac OS. The library is supported on all major operating systems: Windows, Linux and Mac OS.