add -Wno-error=implicit-fallthrough and -Wno-error=switch-default to CMAKE_CXX_FLAGS

[mxmilkiib]

fixes half of #726

[morphis]

Ubuntu 16.04 doesn't like this as it seems

cc1plus: error: -Werror=implicit-fallthrough: no option -Wimplicit-fallthrough

Looks like we need to find another solution or make this conditional on the used GCC version.

[morphis]

Looks like -Wno-error=switch-default does what we want on 16.04. Does that work with newer GCC versions too?

[mxmilkiib]

with GCC8 plus both -Wno-error=switch-default and -Wno-error=implicit-fallthrough, the build works.

[morphis]

@milkmiruku Are you going to update the PR with that?

[daedroza]

@milkmiruku : Please remove -Wno-error=implicit-fallthrough first & then add -Wno-error=switch-default, since the switch-default works for both GCC versions.

[mxmilkiib]

without both -Wno-error=switch-default and -Wno-error=implicit-fallthrough, the build fails.

on having just -Wno-error=switch-default, i get;

[ 35%] Building CXX object external/backtrace-cpp/CMakeFiles/backward_object.dir/backward.cpp.o
In file included from /home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.cpp:26:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In member function ‘void backward::StackTraceLinuxImplBase::load_thread_info()’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:517:37: warning: use of old-style cast to ‘size_t’ {aka ‘long unsigned int’} [-Wold-style-cast]
   if (_thread_id == (size_t) getpid()) {
                                     ^
                     -----------------
                     static_cast<size_t> ( getpid())
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In static member function ‘static _Unwind_Reason_Code backward::details::Unwinder<F>::backtrace_trampoline(_Unwind_Context*, void*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:576:22: warning: use of old-style cast to ‘class backward::details::Unwinder<F>*’ [-Wold-style-cast]
   return ((Unwinder*)self)->backtrace(ctx);
                      ^~~~
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In member function ‘_Unwind_Reason_Code backward::details::Unwinder<F>::backtrace(_Unwind_Context*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:591:25: warning: use of old-style cast to ‘void*’ [-Wold-style-cast]
    (*_f)(_index, (void*)ip);
                         ^~
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In member function ‘backward::ResolvedTrace backward::TraceResolverLinuxImpl<backward::trace_resolver_tag::libdw>::resolve(backward::ResolvedTrace)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1153:46: warning: use of old-style cast to ‘Dwarf_Addr’ {aka ‘long unsigned int’} [-Wold-style-cast]
   Dwarf_Addr trace_addr = (Dwarf_Addr) trace.addr;
                                              ^~~~
                           -----------------------
                           reinterpret_cast<Dwarf_Addr> ( trace.addr)
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In member function ‘void backward::TraceResolverLinuxImpl<backward::trace_resolver_tag::libdw>::inliners_search_cb::operator()(Dwarf_Die*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1312:11: warning: switch missing default case [-Wswitch-default]
    switch (dwarf_tag(die)) {
           ^
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In member function ‘void backward::Printer::print_source_loc(FILE*, const char*, const backward::ResolvedTrace::SourceLoc&, void*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1852:58: warning: use of old-style cast to ‘int’ [-Wold-style-cast]
     indent, source_loc.filename.c_str(), (int)source_loc.line,
                                                          ^~~~
                                          -----
                                          static_cast<int> (  )
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In constructor ‘backward::SignalHandling::SignalHandling(const std::vector<int>&)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1908:48: warning: use of old-style cast to ‘char*’ [-Wold-style-cast]
   _stack_content.reset((char*)malloc(stack_size));
                                                ^
                        -------
                        static_cast<char*> (     )
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In static member function ‘static void backward::SignalHandling::sig_handler(int, siginfo_t*, void*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1944:36: warning: use of old-style cast to ‘ucontext_t*’ {aka ‘struct ucontext_t*’} [-Wold-style-cast]
   ucontext_t *uctx = (ucontext_t*) _ctx;
                                    ^~~~
                      -
                      static_cast<-
                                  > (   )
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp: In static member function ‘static Dwarf_Die* backward::TraceResolverLinuxImpl<backward::trace_resolver_tag::libdw>::find_fundie_by_pc(Dwarf_Die*, Dwarf_Addr, Dwarf_Die*)’:
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1391:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
      if (die_has_pc(die, pc)) {
      ^~
/home/milk/pkgs/anbox-git/src/anbox/external/backtrace-cpp/backward.hpp:1394:5: note: here
     default:
     ^~~~~~~
cc1plus: all warnings being treated as errors
make[2]: *** [external/backtrace-cpp/CMakeFiles/backward_object.dir/build.make:63: external/backtrace-cpp/CMakeFiles/backward_object.dir/backward.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1763: external/backtrace-cpp/CMakeFiles/backward_object.dir/all] Error 2
make: *** [Makefile:141: all] Error 2
==> ERROR: A failure occurred in build().

though I can make the change to just -Wno-error=switch-default if the plan isn't to target GCC8 just yet, and recommend to the AUR PKGBUILD maintainer to patch in -Wno-error=implicit-fallthrough

[morphis]

though I can make the change to just -Wno-error=switch-default if the plan isn't to target GCC8 just yet, and recommend to the AUR PKGBUILD maintainer to patch in -Wno-error=implicit-fallthrough

The minimum required GCC version is what is shipped in Ubuntu 16.04. If you don't want to recommend the Arch maintainers to patch Anbox we can detect the GCC version in cmake and add the right flag depending on the version we find.

[mxmilkiib]

I've removed -Wno-error=implicit-fallthrough. I'm not familiar with cmake so will leave the conditional aspect to someone else. anbox-git is the AUR entry (Arch User Repo, rather than official core/extra/community Arch maintainer packages). I'll leave a comment there reflecting the situation. Thanks folks for the assistance :)

[morphis]

@milkmiruku Thanks for all the work!

[HaoZeke]

Actually even with this the dkms modules fail to install on ArchLinux, by not finding ashmem..

[morphis]

@HaoZeke Actually that is a completely different thing. Please open a bug report with more details on the failing build of the kernel modules.

[rodneyrod]

I'm still getting this build failing with AUR on Manjaro. This is just the main package only and its dependencies, nothing else.

[ghost]

As am I.
Kernel: 4.14.48-1-lts