Better toolchain deps

docs/guide/toolchains.rst

+.. highlight:: yaml
+
 Toolchains
 ##########
 
 
 ``:c++UV:XYZ`` (for two integers ``UV``)
     Sets the C++ version to ``C++UV`` and uses the ``:XYZ`` toolchain.
+
+
+Toolchain Definitions
+*********************
+
+Besides using the built-in toolchains, it is likely that you'll soon want to
+customize a toolchain further. Further customization must be done with a
+file that contains the toolchain definition. The most basic toolchain file is
+simply one line:
+
+.. code-block::
+
+    Compiler-ID: <compiler-id>
+
+where ``<compiler-id>`` is one of the known ``Compiler-ID`` options (See the
+toolchain option reference). ``dds`` will infer common suitable defaults for
+the remaining options based on the value of ``Compiler-ID``.
+
+For example, if you specify ``GNU``, then ``dds`` will assume ``gcc`` to be the
+C compiler, ``g++`` to be the C++ compiler, and ``ar`` to be the library
+archiving tool.
+
+If you know that your compiler executable has a different name, you can
+specify them with additional options:
+
+.. code-block::
+
+    Compiler-ID: GNU
+    C-Compiler: gcc-9
+    C++-Compiler: g++-9
+
+``dds`` will continue to infer other options based on the ``Compiler-ID``, but
+will use the provided executable names when compiling files for the respective
+languages.
+
+To specify compilation flags, the ``Flags`` option can be used:
+
+.. code-block::
+
+    Flags: -fsanitize=address -fno-inline
+
+.. note::
+    Use ``Warning-Flags`` to specify options regarding compiler warnings.
+
+Flags for linking executables can be specified with ``Link-Flags``:
+
+.. code-block::
+
+    Link-Flags: -fsanitize=address -fPIE
+
+
+Toolchain Option Reference
+**************************
+
+The following options are available to be specified within a toolchain file:
+
+
+``Compiler-ID``
+---------------
+
+Specify the identity of the compiler. This option is used to infer many other
+facts about the toolchain. If specifying the full toolchain with the command
+templates, this option is not required.
+
+Valid values are:
+
+``GNU``
+    For GCC
+
+``Clang``
+    For LLVM/Clang
+
+``MSVC``
+    For Microsoft Visual C++
+
+
+``C-Compiler`` and ``C++-Compiler``
+-----------------------------------
+
+Names/paths of the C and C++ compilers, respectively. Defaults will be inferred
+from ``Compiler-ID``.
+
+
+``C-Version`` and ``C++-Version``
+---------------------------------
+
+Specify the language versions for C and C++, respectively. By default, ``dds``
+will not set any language version. Using this option requires that the
+``Compiler-ID`` be specified
+
+Valid ``C-Version`` values are:
+
+- ``C89``
+- ``C99``
+- ``C11``
+- ``C18``
+
+Valid ``C++-Version`` values are:
+
+- ``C++98``
+- ``C++03``
+- ``C++11``
+- ``C++14``
+- ``C++17``
+- ``C++20``
+
+.. warning::
+    ``dds`` will not do any "smarts" to infer the exact option to pass to have
+    the required effect. If you ask for ``C++20`` from ``gcc 5.3``, ``dds``
+    will simply pass ``-std=c++20`` with no questions asked. If you need
+    finer-grained control, use the ``Flags`` option.
+
+
+``Warning-Flags``
+-----------------
+
+Override the compiler flags that should be used to enable warnings. This option
+is stored separately from ``Flags``, as these options may be enabled/disabled
+separately depending on how ``dds`` is invoked.
+
+.. note::
+    If ``Compiler-ID`` is provided, a default value will be used that enables
+    common warning levels.
+
+    If you need to tweak warnings further, use this option.
+
+
+``Flags``, ``C-Flags``, and ``C++-Flags``
+-----------------------------------------
+
+Specify *additional* compiler options, possibly per-language.
+
+
+``Link-Flags``
+--------------
+
+Specify *additional* link options to use when linking executables.
+
+
+``Optimize``
+------------
+
+Boolean option (``True`` or ``False``) to enable/disable optimizations. Default
+is ``False``.
+
+
+``Debug``
+---------
+
+Boolean option (``True`` or ``False``) to enable/disable the generation of
+debugging information. Default is ``False``.
+
+
+``Compiler-Launcher``
+---------------------
+
+Provide a command prefix that should be used on all compiler executions.
+e.g. ``ccache``.
+
+
+Advanced Options Reference
+**************************
+
+The options below are probably not good to tweak unless you *really* know what
+you are doing. Their values will be inferred from ``Compiler-ID``.
+
+
+``Deps-Mode``
+-------------
+
+Specify the way in which ``dds`` should track compilation dependencies. One
+of ``GNU``, ``MSVC``, or ``None``.
+
+
+``C-Compile-File``
+------------------
+
+Override the *command template* that is used to compile C source files.
+
+
+``C++-Compile-File``
+--------------------
+
+Override the *command template* that is used to compile C++ source files.
+
+
+``Create-Archive``
+------------------
+
+Override the *command template* that is used to generate static library archive
+files.
+
+
+``Link-Executable``
+-------------------
+
+Override the *command template* that is used to link executables.
+
+
+``Include-Template``
+--------------------
+
+Override the *command template* for the flags to specify a header search path.
+
+
+``External-Include-Template``
+-----------------------------
+
+Override the *command template* for the flags to specify a header search path
+of an external library.
+
+
+``Define-Template``
+-------------------
+
+Override the *command template* for the flags to set a preprocessor definition.