On Mon, 13 Jan 2014, John Peterson wrote:
Is there anything in C++11 that can be treated analogously to the
"LIBMESH_BEST_UNORDERED_MAP" business we've got now? That's
actually been pretty useful in the past.
Very good point. LIBMESH_BEST_UNORDERED_MAP *is* a C++11 feature,
isn't it? Even though we do have a bunch of fallbacks to TR1 and GNU
implementations.
Off the top of my head, the C++11 features I'd really like to use
(auto, range-based for loop syntax, lambdas) don't really lend
themselves to preprocessor detection/macros like this.
Nope.
But what about easing in to the C++11 world with the new
static_assert? We can use configure to see if the compiler supports
it, and then have a libmesh_static_assert that either uses it or
falls back on libmesh_assert as the case may be.
Actually, it's easy to implement a limited static_assert in C++03;
we'd just want to do what we did with AutoPtr so we'd get better error
messages when the standard implementation is available.
Hmmm... there's basically three kinds of C++11 features we can use
with old compilers:
Reimplementable-if-not-found features:
hash tables (done!)
static_assert
is_foo type traits
tuples (within limitations)
shared_ptr
unique_ptr
Ignorable-via-preprocessor-if-not-found features:
constexpr
final
override
rvalue reference argument function overloads
explicit keyword on conversion operators
Fallback-if-not-found features:
strongly typed enumerations
multithreading
deleted member functions
At the very least, this would force us to start a c++11.m4 file of
some kind to test for specific features, which I don't think we have
at the moment...
I've got a catch-all we can use; we'll probably want to have
feature-by-feature tests, though.
---
Roy
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