Incorrect mersenne_twister_engine equality comparison on initial seed states #37817
Description
| Bugzilla Link | 38469 |
| Version | 7.0 |
| OS | All |
| Attachments | Program as described in the Description |
| CC | @mclow |
Extended Description
[rand.req.eng] specifies the comparison between two engines as returning true
if the infinite sequences of values that would be generated by repeated calls
to their respective operator()s are equivalent.
The attached program seeds two mersenne_twister_engines with specific states. It asserts that the values returned by the engines match for some number of calls, and that the engines are considered equivalent after that set of calls.
It then asserts that the engines were equivalent before those calls.
The assertion fails; however, either an earlier assertion should have failed, or the engines before those calls do indeed produce equivalent infinite sequences of values.
Online compiler: https://wandbox.org/permlink/a3frEvZRLgezujN1
=== COMPILER INVOCATION:
clang++ -stdlib=libc++ -std=c++17 -pedantic-errors -Wall -Wextra -Werror -xc++ mteEqSeededStates.cc -o ./a.out
=== RUN SCRIPT:
./a.out
=== EXPECTED RUN OUTPUT:
(Exits with rc=0).
=== ACTUAL RUN OUTPUT:
a.out: mteEqSeededStates.cc:74: int main(): Assertion `enginesCompareEqualOnInit' failed.
=== COMPILER VERSION INFO (clang++ -v):
clang version 8.0.0 (https://github.com/llvm-mirror/clang.git 074cccc152df061007c8500515698b57a5af7103) (https://github.com/llvm-mirror/llvm.git 40868d4)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/wandbox/clang-head/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Selected multilib: .;@m64