I get an error when compile code containing <experimental/any>.
Code in main.cpp:
#include <experimental/any>
int main() { }
Compile this (clang version is 3.9):
clang++ main.cpp -o main -std=c++1z
Error after the compiling:
In file included from main.cpp:2:
/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/experimental/any:364:34: error:
no template named '__any_caster'; did you mean 'any_cast'?
return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
^
/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/experimental/any:361:30: note:
'any_cast' declared here
inline const _ValueType* any_cast(const any* __any) noexcept
^
/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/experimental/any:372:34: error:
no template named '__any_caster'; did you mean 'any_cast'?
return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
^
/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/experimental/any:369:24: note:
'any_cast' declared here
inline _ValueType* any_cast(any* __any) noexcept
^
2 errors generated.
As #chris mentioned in the comments:
You could try with libc++. Perhaps there's an incompatibility with Clang in libstdc++'s new header.
This turns out to be true. Clang 3.9 is still experimental, and so it uses experimental headers, including a experimental C++ standard library. By default, it is provided by GCC, and so an incompatibility occurs between the GCC implementation and the Clang implementation.
Related
I have the following code (intended to detect if the compiler supports C++14):
#include <memory>
#include <algorithm>
// Check the version language macro, but skip MSVC because
// MSVC reports 199711 even in MSVC 2017.
#if __cplusplus < 201402L && !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
#error "insufficient support for C++14"
#endif
int main()
{
auto ptr = std::make_unique<int>(42);
constexpr int max = std::max(0, 1);
(void) ptr;
(void) max;
return 0;
}
When compiling it with g++ (version 11.2.1) and the line g++ -std=c++14 test.cpp -o test it works fine. When compiling it with the intel compiler (version 2021.3.0 (gcc version 11.2.1 compatibility)) instead using icpc -std=c++14 test.cpp -o test, it fails with
In file included from /usr/include/c++/11/cwchar(44),
from /usr/include/c++/11/bits/postypes.h(40),
from /usr/include/c++/11/iosfwd(40),
from /usr/include/c++/11/bits/shared_ptr.h(52),
from /usr/include/c++/11/memory(77),
from test.cpp(1):
/usr/include/wchar.h(155): error: attribute "__malloc__" does not take arguments
__attribute_malloc__ __attr_dealloc_free;
^
In file included from /usr/include/c++/11/cstdlib(75),
from /usr/include/c++/11/bits/stl_algo.h(59),
from /usr/include/c++/11/algorithm(62),
from test.cpp(2):
/usr/include/stdlib.h(565): error: attribute "__malloc__" does not take arguments
__attr_dealloc_free;
^
In file included from /usr/include/c++/11/cstdlib(75),
from /usr/include/c++/11/bits/stl_algo.h(59),
from /usr/include/c++/11/algorithm(62),
from test.cpp(2):
/usr/include/stdlib.h(569): error: attribute "__malloc__" does not take arguments
__THROW __attr_dealloc (reallocarray, 1);
^
In file included from /usr/include/c++/11/cstdlib(75),
from /usr/include/c++/11/bits/stl_algo.h(59),
from /usr/include/c++/11/algorithm(62),
from test.cpp(2):
/usr/include/stdlib.h(797): error: attribute "__malloc__" does not take arguments
__attr_dealloc_free __wur;
^
compilation aborted for test.cpp (code 2)
What exactly is going wrong here, and how can I fix it?
Short update: Looks as if CUDA is running into similar issues, and it might be related to glibc 2.34: https://forums.developer.nvidia.com/t/cuda-11-5-samples-throw-multiple-error-attribute-malloc-does-not-take-arguments/192750/15
Compiling and executing the shared code using icpc 2021.4 and it runs fine.
Used below command to compile the code.
icpc -std=c++14
Below are the environment details.
Operating System: Ubuntu 18.04.3 LTS
Kernel: Linux 4.15.0-76-generic
For compatibility, Kindly refer the link for Intel® C++ Compiler Classic System Requirements
https://software.intel.com/content/www/us/en/develop/articles/oneapi-c-compiler-system-requirements.html
MSYS2's GCC package was recently updated to 9.1, but Clang doesn't like the new <variant> libstdc++ header that comes with it.
When compiling following simple program:
#include <variant>
int main()
{
std::variant<int, float> x;
}
I get:
# clang++ -std=c++17 foo.cpp
In file included from foo.cpp:1:
Z:\...\msys2\mingw64\include\c++\9.1.0\variant:1559:55: error: '__get' is missing exception specification 'noexcept'
friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v);
^
foo.cpp:5:30: note: in instantiation of template class 'std::variant<int, float>' requested here
std::variant<int, float> x;
^
Z:\...\msys2\mingw64\include\c++\9.1.0\variant:263:5: note: previous declaration is here
__get(_Variant&& __v) noexcept
^
1 error generated.
Here is the complete <variant> header if you want to look at it.
While I'm waiting for an official fix, I did as Clang suggested and added noexcept to the header.
It seems to work so far.
Can this solution cause any problems? Should I do something else?
Bonus points if you know if it's a libstdc++ bug or a Clang bug.
The fix is correct. It's a libstdc++ bug, see https://bugs.llvm.org/show_bug.cgi?id=41863 and https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90397
Trying to compile the sqlpp17 codebase with gcc 8.2.1 and clang 6.0.1 have been a really strange experience. The code pushes the compilers to the limits and I hit probably a few compiler bugs in the meantime.
From the GCC Docs, [[maybe_unused]] is implemented since version 7, but if used this way:
struct foo {
foo([[maybe_unused]] bool thing1)
{
}
};
I hit this specific error:
<source>:2:9: error: expected unqualified-id before '[' token
foo([[maybe_unused]] bool thing1)
^
<source>:2:9: error: expected ')' before '[' token
foo([[maybe_unused]] bool thing1)
~^
)
Compiler returned: 1
Now, I know too little about C++17 to know if this error is correct, I know that clang 6 compiles that part fine (and fails somewhere else).
So, who's right, clang or gcc? (flags are -std=gnu++17 for both clang and gcc, generated by CMake)
This is a known bug in g++: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81429 G++ doesn't parse correctly [[maybe_unused]] attribute for first argument of the constructor.
I have the following code:
#include <type_traits>
int main()
{
}
g++ file.cc -std=c++0x
works just fine.
However, I need to use clang++ for some reason.
When I try
clang++ file.cc -std=c++0x
I get a bunch of errors:
In file included from file.cc:1:
In file included from /usr/include/c++/4.4.4/type_traits:50:
/usr/include/c++/4.4.4/tr1_impl/type_traits:230:41: error: expected ')'
struct is_function<_Res(_ArgTypes......)>
^
/usr/include/c++/4.4.4/tr1_impl/type_traits:230:28: note: to match this '('
struct is_function<_Res(_ArgTypes......)>
^
/usr/include/c++/4.4.4/tr1_impl/type_traits:230:12: error: redefinition of 'is_function<type-parameter-0-0 (type-parameter-0-1, ...)>'
struct is_function<_Res(_ArgTypes......)>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/4.4.4/tr1_impl/type_traits:227:12: note: previous definition is here
struct is_function<_Res(_ArgTypes...)>
^
/usr/include/c++/4.4.4/tr1_impl/type_traits:233:29: error: type qualifier is not allowed on this function
struct is_function<_Res(_ArgTypes...) const>
....
clang++ --version gives:
clang version 2.8 (branches/release_28)
Target: x86_64-redhat-linux-gnu
Thread model: posix
Any ideas how to fix that? (-std=c++11 doesn't work, not recognized.)
Clang 2.8 does not support C++11 features, you need to upgrade your compiler to use them.
I try to compile the simple code
#include <atomic>
int bar = 0;
void foo(std::atomic<int>&flag)
{ bar = flag; }
with clang++ 3.2 (downloaded as llvm 3.2 from llvm.org; on mac os.x 10.8.3 this fails with the error
/> clang++ -std=c++11 -stdlib=libc++ -O3 -march=native -c test.cc
In file included from test.cc:1:
/usr/include/c++/v1/atomic:576:17: error: first argument to atomic operation must be a pointer to non-const _Atomic type ('const _Atomic(int) *' invalid)
{return __c11_atomic_load(&__a_, __m);}
^ ~~~~~
/usr/include/c++/v1/atomic:580:53: note: in instantiation of member function
'std::_1::_atomic_base::load' requested here
operator _Tp() const _NOEXCEPT {return load();}
^
test.cc:5:9: note: in instantiation of member function 'std::_1::_atomic_base::operator int' requested here
bar = done;
When I use /usr/bin/clang++ instead (which comes with the OS or Xcode) it compiles just fine. The libc++ is that at /usr/lib/c++/v1 in both cases.
What am I missing? Is there another libc++ that comes with llvm 3.2 but which I'm missing? (I cannot find anything in the clang3.2 tree).
Xcode now bundles libc++ within the Xcode.app directory. You can inspect this directory by control-clicking Xcode.app and choose "Show Package Contents".