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C++17 library facilities for older compilers

CMake 0.61% C++ 99.39%

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cpp17_headers's Issues

libc++ missing symbols for bad_optional_access()

I don't know what, if anything, can be done about this but if you build on OS X with clang from Apple LLVM 7.3.0 (which comes with Xcode 7.3.1) and you use the experimental/optional header that comes with clang, then you'll get undefined symbol errors at link time if you use the optional::value() method (which needs to throw on bad references) ... here CppUtilTest.cpp is a test program I wrote to verify some local templates that use optional<>.

Undefined symbols for architecture x86_64:
  "std::experimental::bad_optional_access::~bad_optional_access()", referenced from:
/**
      CppUtilLookupTests_lookupStdFind_Test::TestBody() in CppUtilTest.cpp.o
      CppUtilLookupTests_lookupSpecialFind_Test::TestBody() in CppUtilTest.cpp.o
  "typeinfo for std::experimental::bad_optional_access", referenced from:
      CppUtilLookupTests_lookupStdFind_Test::TestBody() in CppUtilTest.cpp.o
      CppUtilLookupTests_lookupSpecialFind_Test::TestBody() in CppUtilTest.cpp.o
  "vtable for std::experimental::bad_optional_access", referenced from:
      CppUtilLookupTests_lookupStdFind_Test::TestBody() in CppUtilTest.cpp.o
      CppUtilLookupTests_lookupSpecialFind_Test::TestBody() in CppUtilTest.cpp.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture x86_64

I had to either go back to using the replacement optional.hpp from here, or else add this to my implementation (in the right namespace)

    bad_optional_access::~bad_optional_access() _NOEXCEPT = default;

Not sure what, if anything, can be done about this because I'm not sure if there's any reliable way to test for it being missing.

Missing string_view literals

I miss them, literally.

cppreference std::literals::string_view_literals::operator""sv

No <filesystem>

It'd be good if we could get that as well

Missing using for std::nullopt in the namespace

For implementations which have <optional> or <experimental/optional>, you need to add:

using std::nullopt;

and

using std::experimental::nullopt;

to the STX_NAMESPACE_NAME otherwise those aren't available in the right namespace.

Increased testing coverage

It would be really great if we could expand the test coverage of the package to test more combinations of things: for example, if we can build/run tests with C++14 support, and with extensions enabled and disabled, and test both with (as now) and without forcing the internal versions to be used so we can verify the support for the native <experimental/*> headers when they're available.

The latter can be tested by just building the test files multiple times with different -D options to enable/disable the internal versions, but building with different levels of C++ support and enable/disable extensions might require multiple invocations of cmake since it doesn't seem you can just reset these values at build time... gross. Maybe adding some info to the README or including a script that will use out-of-source-tree builds to run cmake/compile multiple ways.

Also, it would be nice if we can enhance the test main() methods to show some info about which model we used to compile, e.g. whether the test used the native implementation vs. the stx implementation.

optional::has_value feature request

The repository at https://github.com/akrzemi1/Optional has a few new changes to optional, namely reset() and has_value(). Any chance we could get a refresh merged into this repository? I could work up a PR if that's helpful.

variant & optional mutually incompatible

Both headers declare std::in_place_t.

in_place_t / in_place_type / etc. failing to compile

I expect you're aware already but trying to compile test_all_includes.cpp with either clang 3.8 or g++ 5.4 or 6.2 gives errors about redefinitions of in_place* symbols:

[ 30%] Building CXX object test/CMakeFiles/test_all_includes.dir/test_all_includes.cpp.o
In file included from cpp17_headers/test/test_all_includes.cpp:12:0:
cpp17_headers/include/stx/variant.hpp:102:27: error: redefinition of 'struct stx::in_place_type_t<T>'
 template <class T> struct in_place_type_t {
                           ^~~~~~~~~~~~~~~
In file included from cpp17_headers/test/test_all_includes.cpp:6:0:
cpp17_headers/include/stx/optional.hpp:288:27: error: previous definition of 'struct stx::in_place_type_t<T>'
 template <class T> struct in_place_type_t {
                           ^~~~~~~~~~~~~~~
In file included from cpp17_headers/test/test_all_includes.cpp:12:0:
cpp17_headers/include/stx/variant.hpp:108:28: error: redefinition of 'struct stx::in_place_index_t<I>'
 template <size_t I> struct in_place_index_t {
                            ^~~~~~~~~~~~~~~~
In file included from cpp17_headers/test/test_all_includes.cpp:6:0:
cpp17_headers/include/stx/optional.hpp:293:28: error: previous definition of 'struct stx::in_place_index_t<I>'
 template <size_t I> struct in_place_index_t {
                            ^~~~~~~~~~~~~~~~

In clang we see:

[ 30%] Building CXX object test/CMakeFiles/test_all_includes.dir/test_all_includes.cpp.o
In file included from cpp17_headers/test/test_all_includes.cpp:12:
cpp17_headers/include/stx/variant.hpp:102:27: error:
      redefinition of 'in_place_type_t'
template <class T> struct in_place_type_t {
                          ^
cpp17_headers/include/stx/optional.hpp:288:27: note:
      previous definition is here
template <class T> struct in_place_type_t {
                          ^
In file included from cpp17_headers/test/test_all_includes.cpp:12:
cpp17_headers/include/stx/variant.hpp:106:30: error:
      redefinition of 'in_place_type'
constexpr in_place_type_t<T> in_place_type{};
                             ^
cpp17_headers/include/stx/optional.hpp:300:30: note:
      previous definition is here
constexpr in_place_type_t<T> in_place_type{};
                             ^
In file included from cpp17_headers/test/test_all_includes.cpp:12:
cpp17_headers/include/stx/variant.hpp:108:28: error:
      redefinition of 'in_place_index_t'
template <size_t I> struct in_place_index_t {
                           ^
cpp17_headers/include/stx/optional.hpp:293:28: note:
      previous definition is here
template <size_t I> struct in_place_index_t {
                           ^
In file included from cpp17_headers/test/test_all_includes.cpp:12:
cpp17_headers/include/stx/variant.hpp:112:31: error:
      redefinition of 'in_place_index'
constexpr in_place_index_t<I> in_place_index{};
                              ^
cpp17_headers/include/stx/optional.hpp:302:31: note:
      previous definition is here
constexpr in_place_index_t<I> in_place_index{};
                              ^

string_view and any do not work with libstdc++ in C++11 mode

libstdc++'s implementations of std::experimental::string_view and std::experimental::any (and optional) require C++14, and will static assert if the compiler is in C++11 mode.

This is not a problem for any, as libc++ doesn't have an implementation, so we can just test for __GNUC__ and __cplusplus < 201402 and be done with it.

It's also not a problem for optional, as neither libc++ or libstdc++'s versions work in C++11 mode so can use the same test.

It's trickier for string_view, because libc++'s implementation does work with C++11, so we'd prefer to use that if possible. We therefore need to check for the symbol __GLIBCXX__ instead (that is, checking for libstdc++ specifically, not just a GCC-compatible compiler), which requires including some standard library header. I'm not sure what a good candidate would be, because unfortunately the "empty" headers like <cstdbool> and <ciso464> don't appear to have this symbol defined.

tcbrindle / cpp17_headers Goto Github PK

cpp17_headers's People

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cpp17_headers's Issues

libc++ missing symbols for bad_optional_access()

Missing string_view literals

No <filesystem>

Missing using for std::nullopt in the namespace

Increased testing coverage

optional::has_value feature request

variant & optional mutually incompatible

in_place_t / in_place_type / etc. failing to compile

string_view and any do not work with libstdc++ in C++11 mode

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