= !MapGuide RFC 172 - Adopt C++11 as the minimum compiler language version =

This page contains a change request (RFC) for the !MapGuide Open Source project.
More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.

== Status ==

||RFC Template Version||(1.0)||
||Submission Date||23 May 2019||
||Last Modified||23 May 2019||
||Author||Jackie Ng||
||RFC Status||draft||
||Implementation Status||||
||Proposed Milestone||4.0||
||Assigned PSC guide(s)||(when determined)||
||'''Voting History'''||(vote date)||
||+1||||
||+0||||
||-0||||
||-1||||
||no vote|| ||

== Overview ==

This RFC proposes to switch to
[http://en.wikipedia.org/wiki/C%2B%2B11 C++11] compilation mode as
default throughout the whole C++ source code of MapGuide.

The goal of this RFC is to request and achieve agreement on using
C++11 as the minimum required version of the C++ programming language
standard.

== Motivation ==

C++11 is the first major update of the C++ standard since 1998. (?C++03 was a bug fix release.)

Having fewer versions of C++ to support will reduce the load on developers and testing systems.

C++11 features aim to promote writing clean, compact, type-safe and fast code. It also delivers better feature-wise compatibility with the C language (C99).

The Wikipedia article at ?http://en.wikipedia.org/wiki/C++11 does a great job describing all changes in C++11 extensively.

The std::auto_ptr smart pointer, together with a bunch of other features, were deprecated and will be removed from C++17. Features like std::unique_ptr provide much stronger replacements.

Enabling C++11 compilation mode will improve the programming environment making it much friendlier than C++98.

A social factor: since (many) C++ programmers no longer enjoy C++98, allowing C++11 mode may increase potential for new contributions.

From a purely-MapGuide perspective:

 * Establishing C++11 as the baseline puts us in a place to finally take advantage of some libraries which we couldn't in the past (hindering development of some new features as a result) as those libraries themselves require a C++11 compliant compiler to build.
 * Also FDO implicitly now requires a C++11 compliant compiler on Linux anyways due to the removal of boost and replacing them with C++11 standard library features (eg. `std::mutex`), so it make some sense to be on the same page regarding the expected C++ standards compilation mode.

== Compilers Landscape ==

Summary of compilers supported by MapGuide with their minimal versions
required to compile source code based on

http://en.cppreference.com/w/cpp/compiler_support C++11 features.

=== C++11 ===
 
||GCC  ||4.8.1+      ||[https://gcc.gnu.org/projects/cxx-status.html#cxx11 C++11 status]    ||Debian 8 (stable), Ubuntu 15.04+, Ubuntu 14.04 `ppa:ubuntu-toolchain-r/test`, Fedora 19+, RHEL7 ||
||Clang||3.3+        ||[https://clang.llvm.org/cxx_status.html#cxx11 C++11 status]          ||Debian 8 (stable), Ubuntu 14.04+, Fedora 19+, CentOS 6(?)||
||MSVC ||14.0+ (2015)||[https://msdn.microsoft.com/en-us/library/hh567368.aspx C++11 status]||n/a||

=== C++14 ===

The C++14 compilers are listed for comparison only:

||GCC  ||4.9+ ||
||Clang||3.4+ ||
||MSVC ||14.0+ (2015)||

== Proposed Solution ==

Windows: No changes required.

Linux/CMake: The CMake build will set default compiler flags to build in C++11 standards mode.

Actual porting of the MapGuide codebase to take advantage of C++11 language features and constructs is not in the scope of this RFC. This RFC is merely seeking consensus that we should now require a C++11 compliant compiler as a minimum requirement to build MapGuide.

The porting of the codebase will be an on-going activity done after adoption of this RFC.

== Implications ==

Windows is not impacted, we will not make any compiler settings changes.

When compiling on Linux, a C++11-compliant compiler is now required.

== Test Plan ==

Verify existing test suites still pass on Linux after activating C++11 compilation mode.

== Funding / Resources ==

Community