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 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 ​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+	​C++11 status	Debian 8 (stable), Ubuntu 15.04+, Ubuntu 14.04 ppa:ubuntu-toolchain-r/test, Fedora 19+, RHEL7
Clang	3.3+	​C++11 status	Debian 8 (stable), Ubuntu 14.04+, Fedora 19+, CentOS 6(?)
MSVC	14.0+ (2015)	​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