make install fails on gcc 7.1.1-64bit

[furkanusta]

Hi, I've just learned about this library and decided to try. However, 'make install' failed in various occasions

First:
cereal/archives/json.hpp:211:33: warning: this statement may fall through [-Wimplicit-fallthrough=]
and failed because CMake sets -Werror by default.

After disabling it, it couldn't find <gnu/stubs-32.h> in cereal/unittests/memory.cpp:28
After installing 32-bit development libraries for glibc (I am on a 64-bit system), it passed that one and failed at

Linking CXX executable test_memory_32:
cannot find -lgcc

I suppose I need to recompile gcc with multilib support to fix this because I couldn't find gcc-multilib in openSuse repositories. It would be quite useful if cereal didn't require 32-bit libraries in an 64-bit system.

I've installed the library and skipped tests for now, but I thought it would be useful to share my experience.

If any more information is needed to reproduce, I can provide

[erichkeane]

Are you attempting to compile 'master' or a different directory? The 28th line of memory.cpp is "#include "memory.hpp", which includes "common.hpp", but a grep of the source base doesn't show a single reference to stubs-32.h.

As far as the fallthrough, it seems that we disable it in rapidjson/internal/regex.h (possibly not re-enabling it?), but a fresh compile of cereal seems to work for me. However, it DOES seem that we still have the problem in the code, so perhaps the disable is working?

[erichkeane]

Additionally, I note the disable in regex.h is only #ifdef clang.

[furkanusta]

First of all I am sorry that I got the stacktrace backwards and it looks like gnu/stubs came from type_traits in libstdc++, but 32-bit libraries still were a problem. I am not sure if it is a compiler, cmake or library bug but it required 32-bit libstdc++ and 32-bit gcc. After installing both of those, now make works fine.

I'll update here after make and the tests finish

[AzothAmmo]

Apparently the fallthrough warning is new in GCC 7 (https://dzone.com/articles/implicit-fallthrough-in-gcc-7). We actually do want the switch statement to fall through here - since the [[fallthrough]] attribute is c++17, it looks like the easiest fix is to add a /* fall through */ comment before appropriate cases.

cereal doesn't actually require 32 bit to work, we just try to build unit tests for both 32 and 64 bit. You can disable the 32 bit tests with the CMAKE flag SKIP_PORTABILITY_TEST.

[furkanusta]

It looks like 32-bit library thing is related to gcc and reported Bug 54444, and I am supposing gcc-32 bit is necessary for linkers (though not sure). However, after installing both it now completed all of the tests without an error

[AzothAmmo]

merged PR to fix