Travis: system includes not treated as such by gcc on osx

[bchretien]

Compilation currently fails on Travis with osx + gcc-4.8. It seems that system includes (e.g. -isystem /usr/include) end up being treated as normal includes (-I/usr/include), and warnings in Eigen become errors.

Scanning dependencies of target roboptim-core
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f src/CMakeFiles/roboptim-core.dir/build.make src/CMakeFiles/roboptim-core.dir/build
/usr/local/Cellar/cmake/2.8.12.2/bin/cmake -E cmake_progress_report /tmp/_travis/build/CMakeFiles 44
[  1%] Building CXX object src/CMakeFiles/roboptim-core.dir/finite-difference-gradient.cc.o
cd /tmp/_travis/build/src && /usr/local/bin/g++-4.8   -Droboptim_core_EXPORTS --coverage -Werror  -pedantic -Wno-long-long -Wall -Wextra -Wcast-align -Wcast-qual -Wformat -Wwrite-strings -Wconversion -DROBOPTIM_DO_NOT_CHECK_ALLOCATION -fvisibility=hidden -fPIC -I/tmp/_travis/build -I/tmp/_travis/build/include -I/Users/travis/build/roboptim/roboptim-core/include -I/usr/local/include -I/tmp/_travis/install/include/eigen3 -I/usr/local/Cellar/log4cxx/0.10.0/include     -I/tmp/_travis/install/include/eigen3 -I/usr/local/Cellar/log4cxx/0.10.0/include -o CMakeFiles/roboptim-core.dir/finite-difference-gradient.cc.o -c /Users/travis/build/roboptim/roboptim-core/src/finite-difference-gradient.cc
/usr/local/Cellar/cmake/2.8.12.2/bin/cmake -E cmake_progress_report /tmp/_travis/build/CMakeFiles 45
[  2%] Building CXX object src/CMakeFiles/roboptim-core.dir/generic-solver.cc.o
cd /tmp/_travis/build/src && /usr/local/bin/g++-4.8   -Droboptim_core_EXPORTS --coverage -Werror  -pedantic -Wno-long-long -Wall -Wextra -Wcast-align -Wcast-qual -Wformat -Wwrite-strings -Wconversion -DROBOPTIM_DO_NOT_CHECK_ALLOCATION -fvisibility=hidden -fPIC -I/tmp/_travis/build -I/tmp/_travis/build/include -I/Users/travis/build/roboptim/roboptim-core/include -I/usr/local/include -I/tmp/_travis/install/include/eigen3 -I/usr/local/Cellar/log4cxx/0.10.0/include     -I/tmp/_travis/install/include/eigen3 -I/usr/local/Cellar/log4cxx/0.10.0/include -o CMakeFiles/roboptim-core.dir/generic-solver.cc.o -c /Users/travis/build/roboptim/roboptim-core/src/generic-solver.cc
In file included from /tmp/_travis/install/include/eigen3/Eigen/Core:259:0,
                 from /Users/travis/build/roboptim/roboptim-core/include/roboptim/core/function.hh:35,
                 from /Users/travis/build/roboptim/roboptim-core/include/roboptim/core/problem.hh:36,
                 from /Users/travis/build/roboptim/roboptim-core/include/roboptim/core/generic-solver.hh:32,
                 from /Users/travis/build/roboptim/roboptim-core/src/generic-solver.cc:22:
/tmp/_travis/install/include/eigen3/Eigen/src/Core/MathFunctions.h: In static member function 'static Scalar Eigen::internal::random_default_impl<Scalar, false, true>::run()':
/tmp/_travis/install/include/eigen3/Eigen/src/Core/MathFunctions.h:511:61: error: conversion to 'int' from 'long unsigned int' may alter its value [-Werror=conversion]
     enum { rand_bits = floor_log2<(unsigned int)(RAND_MAX)+1>::value,
                                                             ^
cc1plus: all warnings being treated as errors
make[2]: *** [src/CMakeFiles/roboptim-core.dir/generic-solver.cc.o] Error 1
make[1]: *** [src/CMakeFiles/roboptim-core.dir/all] Error 2
make: *** [all] Error 2

Possible related issue: http://public.kitware.com/Bug/view.php?id=10837

[bchretien]

Indeed, at the end of /usr/share/cmake-3.0/Modules/Compiler/GNU.cmake (whatever the path for your distribution):

  if(NOT APPLE)
    set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
  endif()

If this is just it, we can simply patch that in the jrl-cmakemodules, but someone on Mac OS X would need to test it first. Note that Clang.cmake does support -isystem, so the stock gcc with the clang backend does not have this problem.

[thomas-moulard]

So the patch would be to always disable "-Werror" on Mac OS X, I guess?
If I understand correctly the ticket "-isystem" is not supported which means that there is almost no way to compile roboptim-core on Mac OS X with the default setup?

[bchretien]

Apparently, -isystem is supported. It may not have been the case 7 years ago when this was added, but I guess it is now... Someone with Mac OS X could check. So we either disable -Werror or enable -isystem for OS X. The latter seems better if we're sure that this is indeed supported.

[bchretien]

Apparently, this was finally fixed in CMake 3.6.