Eigen & GCC 5 : class std::binder2nd is deprecated

Question

I just restarted working on a project which has been on hold for a few months. Last time I compiled it it was working just fine, without any error nor warning. Yet when I tried to compile it earlier today I got this warning

attention : ‘template<class _Operation> class std::binder2nd’ is deprecated [-Wdeprecated-declarations]

This warning literally appears hundreds of time when including Eigen/Geometry, which I use all over my project

In file included from [...]/include/Eigen/src/Core/ArrayBase.h:109:0,
                 from [...]/include/Eigen/Core:350,
                 from [...]/include/Eigen/Geometry:4,
                 from [...]/include/[myproject]/types.hh:8,
                 from [...]/include/[myproject]/voronoi.hh:8

Since then I haven't updated Eigen (is used 3.2.4 which is still the last update today). However, since last time I compiled it, GCC has been updated to 5.1.0 (I'm using archlinux)

Question:

• Is there an issue with gcc 5.1.0 telling me std::binder2nd is deprecated
• Should Eigen be updated ?
• How can I silent those specific warning without loosing the verbosity of my build ?

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ANSWER

I appreas that std::bind2nd is really deprecated and that a commit has been done to solve that in Eigen. This commit is however not yet merged with the master branch :/ (and doesn't solve the issue as some std::bind2nd are still present in Eigen's code)

Bottom line is: Eigen's last stable version is deprecated

Answer 1

• Is there an issue with gcc 5.1.0 telling me std::binder2nd is deprecated

No, the C++ standard says it's deprecated in C++11, so if you compile in C++11 mode then it is supposed to be deprecated.

• Should Eigen be updated ?

Yes. if it wants to be C++17 compatible, as std::bind2nd doesn't exist post-C++14 at all.

• How can I silent those specific warning without loosing the verbosity of my build ?

Suppress the warning. Either compile with -Wno-deprecated-declarations on the command-line or do it in the source when including the Eigen headers:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#include <eigen/whatever.h>
#pragma GCC diagnostic pop

Or, as the other answer says, tell GCC to treat the Eigen headers as system headers, which happens automatically if they are in /usr/include, or are included with -isystem, or are included from another header that does:

#pragma GCC system_header
#include <eigen/whatever.h>

Answer 2

How can I silent those specific warning without loosing the verbosity ?

Edit the CMakeLists.txt file. Add this line somewhere after CMAKE_CXX_FLAGS is set.

SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated-declarations")

Previous answer mentioned adding this to #pragma or to command line. I am biased against #pragma because I find it hard later on to remember where I put it. So as general practice, I try to avoid #pragma. Adding to command line means you have to remember to type this everytime you recompile.