[cfe-commits] [Patch][Review] constexpr-ification of <limits> and random number generators

Jonathan Sauer jonathan.sauer at gmx.de
Mon Apr 2 12:10:24 PDT 2012


>> Oh, no problem: First of all adapting my patch took me about 10 minutes, and second of all I did it on a whim,
>> so any unnecessary work done by me is my own fault :-)
>> I prepared a new patch using _LIBCPP_CONSTEXPR and have it attached. Please review and, if ok, commit.
> Thanks.  Two problems:
> 1.  Please include a patch to CREDITS.TXT
> 2.  Please test /test/numerics/rand and test/language.support/support.limits with constexpr turned off (say in C++03 mode).  I'm getting many failures under rand.

support.limits tests successfully with C++03. I fixed the few missing "const" in <random>, but since
some of the static constants depend on method calls (namely to min() and max()), they won't compile
with C++03 at all.

It would be possible, of course, to conditionally define those constants to either use min() and max()
or _Min and _Max, respectively:

    static const result_type _Min = _Engine::_Min;
    static const result_type _Max = _Engine::_Max;
    static _LIBCPP_CONSTEXPR const result_type _Min = _Engine::min();
    static _LIBCPP_CONSTEXPR const result_type _Max = _Engine::max();

But this would depend on the non-standard members _Min and _Max. And it would complicate the source, too.

What do you think? I attached a modified patch for <limits> and CREDITS.TXT, since I guess they are okay
in either case.

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P.S: Testing with C++03, the files language.support/support.start.term/quick_exit.pass.cpp and
language.support/support.types/nullptr_t.pass.cpp fail to compile here:

quick_exit.pass.cpp:19:10: error: no member named 'at_quick_exit' in namespace 'std'
quick_exit.pass.cpp:20:5: error: use of undeclared identifier 'quick_exit'
2 errors generated.
/Users/rynnsauer/LLVM/libcxx/test/language.support/support.start.term/quick_exit.pass.cpp failed to compile
Compile line was: /Users/rynnsauer/LLVM/build/Release+Asserts/bin/clang++ -stdlib=libc++ quick_exit.pass.cpp

nullptr_t.pass.cpp:57:24: error: reinterpret_cast from 'std::__1::nullptr_t' to 'std::ptrdiff_t'
      (aka 'long') is not allowed
    std::ptrdiff_t i = reinterpret_cast<std::ptrdiff_t>(nullptr);
1 error generated.
/Users/rynnsauer/LLVM/libcxx/test/language.support/support.types/nullptr_t.pass.cpp failed to compile
Compile line was: /Users/rynnsauer/LLVM/build/Release+Asserts/bin/clang++ -stdlib=libc++ nullptr_t.pass.cpp

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