error: no member named 'max_align_t' in the global namespace

[danpolanco]

I think this has to do with this issue:
clang-3.5: once gcc-4.9 and g++-4.9 are installed, clang stops properly building existing projects

I tried adding set (CMAKE_C_COMPILER "/usr/bin/clang") to the catch CMakeLists.txt, but it still output this:

In file included from /data/house_data/human_low_copy/tests/general_test.cpp:2:
In file included from /data/house_data/human_low_copy/build/catch/src/catch/include/catch.hpp:28:
In file included from /data/house_data/human_low_copy/build/catch/src/catch/include/internal/catch_capture.hpp:11:
In file included from /data/house_data/human_low_copy/build/catch/src/catch/include/internal/catch_result_builder.h:91:
In file included from /data/house_data/human_low_copy/build/catch/src/catch/include/internal/catch_expression_lhs.hpp:12:
In file included from /data/house_data/human_low_copy/build/catch/src/catch/include/internal/catch_evaluate.hpp:16:
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/cstddef:51:11: error: no member named 'max_align_t' in the global namespace
using ::max_align_t;
~~^
1 error generated.
make[2]: *** [tests/CMakeFiles/general_test.dir/general_test.cpp.o] Error 1
make[1]: *** [tests/CMakeFiles/general_test.dir/all] Error 2
make: *** [all] Error 2

I also change my alternatives (Ubuntu) for gcc / g++ to 4.8 so that gcc --version && g++ --version both return gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2 and g++ (Ubuntu 4.8.2-19ubuntu1) 4.8.2. But it still pops the error up.

Any idea how to get it to use 4.8? Or how I might solve this problem else-how?

Edit:
Btw, I'm sorry if this is the wrong place for this. I thought you guys might have run into this problem already and therefore know a solution. Plus, I want to have this recorded in the issues so if someone else has the same problem, they know how to fix it.

[danpolanco]

I'm not sure what I changed to fix it, but it is working now. It might have been that I changed clang from 3.4 to 3.5... It's hard to say. If I figure it out, I'll let you all know.

[philsquared]

For the record this is not something I've seen before. In any case it doesn't appear to be really a "Catch" thing - although perhaps something about the way Catch includes std lib headers brought it out? The max_align_t does not appear in Catch, at least.

Glad you got it sorted, though.

[martinmoene]

To give (or get) moral support, I'm experiencing similarly unexpected behaviour from clang/libc++ (at Travis). See lest issue #10.

[danpolanco]

What is odd is that I figured out a way to get around it... But it's annoying.

I'm using cmake and it downloads catch on the fly using ExternalProgram_Add as per the instructions. In any case, I call cmake and then make and it works fine for the initial build. Then, if call I cmake and make again without removing all of the files, it throws that error.

So right now, I just rm -rf * my build folder and then cmake and make again....

[PureAbstract]

@DanTheColoradan This isn't a Catch issue - it's a compiler/library mismatch issue.

There's no requirement that compiler A be interoperable with compiler B's stdlib implementation, and although the Clang folks certainly go out of their way to ensure their compiler works with gcc's libstdc++, you've stumbled across a mismatch. I'd recommend using libc++ with clang, and libstdc++ with gcc.

3.11.2 requires that std::max_align_t is defined, but not that there's a definiton in the global namespace; It seems that the version of libstdc++ that you're using expects it to be defined globally in order to define it in std.

I tried adding set (CMAKE_C_COMPILER "/usr/bin/clang") to the catch CMakeLists.txt, but it still output this:

That sets CMake's C compiler, not the C++ compiler; you may want to try adding set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
however...

I'm using cmake and it downloads catch on the fly using ExternalProgram_Add as per the instructions. In any case, I call cmake and then make and it works fine for the initial build. Then, if call I cmake and make again without removing all of the files, it throws that error.

I've seen cases where setting CMAKE_C_COMPILER and CMAKE_CXX_COMPILER in CMakeLists.txt doesn't do the right thing (I don't recall the exact details, but ISTR it has something to do with where you set then). As you've found, re-running cmake in an existing cmake tree isn't quite the same operation as running cmake in a fresh directory - and I think this may be one of the problem cases.

You may want to consider trying:
cmake -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++

I just rm -rf * my build folder and then cmake and make again....
Firstly, you typically don't need to re-run cmake in an esiting build tree - running make is usually sufficient (since it invokes cmake to see if cmake needs to be re-run...).
Secondly, you may well find that rm build/CMakeCache.txt before re-running cmake is enough, rather than blowing away the whole build tree.

[danpolanco]

Thanks! I'll give it a go.

And as I mentioned, I'm definitely not claiming it's a catch issue. I mostly wanted to double check it wasn't, and also leave a record for anyone who stumbles upon this problem.

I'll give your suggestions a thorough testing and leave it at that :)

Thanks again! 👍

[philsquared]

Thanks Andy (@PureAbstract) - I missed that the compiler and std libs were being mixed up that way.
Not sure it helps Martin, though

[PureAbstract]

@philsquared I think @martinmoene 's actually having a related issue (i.e. travis mixing clang w/libstdc++) - but it can be a bit harder to figure out what's going on with travis :-).

[PureAbstract]

@DanTheColoradan Hope it was of some help - the CMake FAQ summarises the CMAKE_CXX_COMPILER issue here - http://www.cmake.org/Wiki/CMake_FAQ#How_do_I_use_a_different_compiler.3F

[danpolanco]

It was. I was able to get a little further after reading that documentation, but it was still acting funny. So, I've decided against using clang on linux and I'm just going to use gcc for now. I think that's a better choice anyway since I'll be forced to compile with at least two compilers (i.e. clang on my mac and gcc on linux).

I really appreciate your help.

Edit: by linux I mean Ubuntu ;-)

[Zmq0max]

@DanTheColoradan You are right. Updating to clang 3.6 fixed it. Thanks