Switch to C++14 and devtoolset-6

Implements RFC-332

Author: Pim Schellart

coding/cpp_style_guide.rst

@@ -84,10 +84,29 @@ These tasks are made much simpler if the code is easily readable and well-docume
 
 .. _style-guide-cpp-2-2:
 
-2-2. We are writing C++11/14 with some restrictions.
-----------------------------------------------------
+2-2. We are writing C++14
+-------------------------
 
-The official policy on the use of C++11 features is at :ref:`Policy on use of C++11/14 language features <style-guide-cpp-cpp-11-14>`.
+The C++11 standard and the C++14 improvements to it bring a number of useful language features that make the resulting code more expressive, easier to read, and safer.
+
+We follow the official: International Standard ISO/IEC 14882:2014(E) – Programming Language C++, without any compiler specific extensions.
+
+.. note::
+
+    Our minimum required compiler versions are:
+
+        * GCC 6.3.1 (Linux)
+        * Clang 800.0.42.1 (macOS)
+
+    these both have complete support for C++14, but in case of compiler bugs the actually allowed set
+    of C++14 features is the intersection of those supported by our compilers and the standard.
+
+.. seealso::
+
+   - :ref:`pipelines:source-install-redhat-legacy` from the `LSST Science Pipelines <https://pipelines.lsst.io>`__ documentation.
+     But note that installation instructions for stack versions 14.0 and below refer to our older baseline compilers.
+     These are now superseded by the minimum required compiler versions listed above.
+   - :doc:`/services/lsst-dev` provides :ref:`instructions for using devtoolset-6 <lsst-dev-tools>` to obtain a more modern GCC on LSST cluster machines.
 
 .. _style-guide-cpp-2-3:
 
@@ -1744,7 +1763,7 @@ This type of implicit conversion can result in incorrect and unintentional side
 5-27a.  Constructor calls SHOULD use C++98 syntax when possible.
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-While C++11 introduces a new syntax for "uniform initialization" using braces, C++ objects in LSST code should be initialized using syntax that is valid in C++98 whenever possible, with brace initialization used only when necessary, such as when initializing aggregates or containers that take ``std::initializer_list`` arguments.
+While a new syntax for "uniform initialization" using braces was introduced with C++11, C++ objects in LSST code should be initialized using syntax that is valid in C++98 whenever possible, with brace initialization used only when necessary, such as when initializing aggregates or containers that take ``std::initializer_list`` arguments.
 
 In particular, default constructors should be called with no parentheses or braces. This avoids most occurrences of the `most-vexing parse problem <https://en.wikipedia.org/wiki/Most_vexing_parse>`_:
 
@@ -2626,23 +2645,6 @@ While it is not expected that we will bring the guts of all legacy code in line
 .. [Google] Google C++ Style Guide, 2017. Available on-line at:
    https://google.github.io/styleguide/cppguide.html
 
-.. _style-guide-cpp-cpp-11-14:
-
-Appendix: Policy on using C++11/14 Features
-===========================================
-
-The C++11 standard and the C++14 improvements to it bring a number of useful language features that make the resulting code more expressive, easier to read, and safer.
-They are becoming well-implemented and widespread.
-C++11/14 features supported by the default compiler provided with the oldest operating system distribution commonly used to install the LSST Stack, currently gcc 4.8.3, may be used at will in ``.cc`` and ``.h`` files.
-
-.. seealso::
-
-   - :ref:`pipelines:source-install-redhat-legacy` from the `LSST Science Pipelines <https://pipelines.lsst.io>`__ documentation.
-   - :doc:`/services/lsst-dev` provides :ref:`instructions for using devtoolset-3 <lsst-dev-tools>` to obtain a more modern GCC on LSST cluster machines.
-   - C++11 compiler support matrix: http://wiki.apache.org/stdcxx/C++0xCompilerSupport.
-
-C++11 uniform initialization syntax should in general *not* be preferred over C++98 construction syntax; see rule :ref:`5-27a <style-guide-cpp-5-27a>`.
-
 .. _style-guide-cpp-using:
 
 Appendix: On Using `Using`

coding/using_boost.rst

@@ -12,16 +12,16 @@ Using Boost
 
 A Boost library may be used only if:
 
-1. the desired effect cannot be accomplished with a C++11 standard language feature, and
-2. a C++ standard library equivalent is either unavailable or unusable with our minimum supported compiler version (i.e. ``gcc`` version 4.8).
+1. the desired effect cannot be accomplished with a C++14 standard language feature, and
+2. a C++ standard library equivalent is either unavailable or unusable with our minimum required compiler version (i.e. ``gcc`` version 6.3.1).
 
-In particular, the following Boost libraries are no longer accepted as they have standard equivalents in gcc 4.8 and above:
+In particular, the following Boost libraries are no longer accepted as they have standard equivalents in gcc 6.3.1 and above:
 
 ``array``
         use ``<array>``
 
 ``bind``
-        prefer C++11 lambda functions instead, but use ``std::bind`` from ``<functional>`` if you must
+        prefer C++14 lambda functions instead, but use ``std::bind`` from ``<functional>`` if you must
 
 ``cstdint``
         use ``<cstdint>``
@@ -30,7 +30,7 @@ In particular, the following Boost libraries are no longer accepted as they have
         use ``<filesystem>``
 
 ``lambda``
-        use C++11 lambda functions
+        use C++14 lambda functions
 
 ``lexical_cast``
         use ``std::to_string``, ``std::stoi``, ``std::stod`` etc.
@@ -51,7 +51,7 @@ In particular, the following Boost libraries are no longer accepted as they have
         use ``std::shared_ptr`` and ``std::unique_ptr`` (and its array specialization) from ``<memory>`` instead of ``boost::shared_ptr``, ``boost::scoped_ptr`` and ``boost::scoped_array``
 
 ``static_assert``
-        use C++11 ``static_assert``
+        use C++14 ``static_assert``
 
 ``tuple``
         use ``<tuple>``

teams/drp.rst

@@ -51,11 +51,11 @@ When connecting to Tiger, you should connect to the head node ``tiger-sumire.pri
 
 Tiger runs version 6.8 of `Springdale Linux <https://puias.math.ias.edu>`_ (a derivative of `RHEL <https://www.redhat.com/en/technologies/linux-platforms/enterprise-linux>`_).
 As such, the default toolchain is too old to work with the LSST stack.
-You should therefore enable ``devtoolset-3`` before proceeding:
+You should therefore enable ``devtoolset-6`` before proceeding:
 
 .. prompt:: bash
 
-  scl enable devtoolset-3 bash
+  scl enable devtoolset-6 bash
 
 A regularly-updated LSST “shared stack” is available in :file:`/tigress/HSC/LSST/stack_tiger/` (note that the name of the cluster is embedded in the path).
 To get started, try:
@@ -74,8 +74,12 @@ Unlike Tiger, there is no head node reserved for HSC/LSST use.
 Connect to ``perseus.princeton.edu``, and be especially considerate of other users before starting long-running jobs on the head node.
 
 Tiger runs version 7.3 of `Springdale Linux <https://puias.math.ias.edu>`_ (a derivative of `RHEL <https://www.redhat.com/en/technologies/linux-platforms/enterprise-linux>`_).
-This provides a default toolchain which is appropriate for working with the LSST stack.
-You should *not* enable ``devtoolset-3`` (or any other ``devtoolset``) when working with LSST code on this system.
+As such, the default toolchain is too old to work with the LSST stack.
+You should therefore enable ``devtoolset-6`` before proceeding:
+
+.. prompt:: bash
+
+  scl enable devtoolset-6 bash
 
 A regularly-updated LSST “shared stack” is available in :file:`/tigress/HSC/LSST/stack_perseus/` (note that the name of the cluster is embedded in the path).
 To get started, try: