Changes between Version 23 and Version 24 of BestPracticeHandbook

Timestamp:

May 14, 2015, 11:41:18 PM (7 years ago)

Author:

Niall Douglas

Comment:

--

BestPracticeHandbook

@@ -951 +951 @@
 These are for a single core 3.9Ghz i7-3770K computer. I think the results speak for themselves, and note that AFIO is only 8k lines with not much metaprogramming.
 
-The approaches for improving build times for your library users are generally as follows:
-
-TODO
+The approaches for improving build times for your library users are generally as follows, and in order of effect:
+
+ 1. Offer a non-header only build configuration:: Here is how many Boost libraries offer both header only and non-header only build configurations by using something like this in their config.hpp:
+
+ {{{#!c++
+// If we are compiling not header only
+#if (defined(BOOST_AFIO_DYN_LINK) || defined(BOOST_ALL_DYN_LINK)) && !defined(BOOST_AFIO_STATIC_LINK)
+
+# if defined(BOOST_AFIO_SOURCE)                // If we are compiling the library binary
+#  undef BOOST_AFIO_HEADERS_ONLY
+#  define BOOST_AFIO_DECL BOOST_SYMBOL_EXPORT    // Mark public symbols as exported from the library binary
+#  define BOOST_AFIO_BUILD_DLL                   // Tell code we are building a DLL or shared object
+# else
+#  define BOOST_AFIO_DECL BOOST_SYMBOL_IMPORT    // If not compiling the library binary, mark public symbols are imported from the library binary
+# endif
+#else                                          // If we are compiling header only
+# define BOOST_AFIO_DECL                         // Do no markup of public symbols
+#endif // building a shared library
+
+
+// Configure Boost auto link to get the compiler to auto link your library binary
+#if !defined(BOOST_AFIO_SOURCE) && !defined(BOOST_ALL_NO_LIB) && \
+    !defined(BOOST_AFIO_NO_LIB) && !AFIO_STANDALONE && !BOOST_AFIO_HEADERS_ONLY
+
+#define BOOST_LIB_NAME boost_afio
+
+// tell the auto-link code to select a dll when required:
+#if defined(BOOST_ALL_DYN_LINK) || defined(BOOST_AFIO_DYN_LINK)
+#define BOOST_DYN_LINK
+#endif
+
+#include <boost/config/auto_link.hpp>
+
+#endif  // auto-linking disabled
+
+
+#if BOOST_AFIO_HEADERS_ONLY == 1                              // If AFIO is headers only
+# define BOOST_AFIO_HEADERS_ONLY_FUNC_SPEC inline               // Mark all functions as inline
+# define BOOST_AFIO_HEADERS_ONLY_MEMFUNC_SPEC inline            // Mark all member functions as inline
+# define BOOST_AFIO_HEADERS_ONLY_VIRTUAL_SPEC inline virtual    // Mark all virtual member functions as inline virtual
+// GCC gets upset if inline virtual functions aren't defined
+# ifdef BOOST_GCC
+#  define BOOST_AFIO_HEADERS_ONLY_VIRTUAL_UNDEFINED_SPEC { BOOST_AFIO_THROW_FATAL(std::runtime_error("Attempt to call pure virtual member function")); abort(); }
+# else
+#  define BOOST_AFIO_HEADERS_ONLY_VIRTUAL_UNDEFINED_SPEC =0;
+# endif
+#else                                                         // If AFIO is not headers only
+# define BOOST_AFIO_HEADERS_ONLY_FUNC_SPEC extern BOOST_AFIO_DECL  // Mark all functions as extern dllimport/dllexport
+# define BOOST_AFIO_HEADERS_ONLY_MEMFUNC_SPEC                      // Mark all member functions with nothing
+# define BOOST_AFIO_HEADERS_ONLY_VIRTUAL_SPEC virtual              // Mark all virtual member functions as virtual (no inline)
+# define BOOST_AFIO_HEADERS_ONLY_VIRTUAL_UNDEFINED_SPEC =0;        // Mark all pure virtual member functions with nothing special
+#endif
+ }}}
+
+ This looks a bit complicated, but isn't really. Generally you will mark up those classes and structs you implement in a .ipp file (this being the file implementing the APIs declared in the header) with `BOOST_AFIO_DECL`, functions with `BOOST_AFIO_HEADERS_ONLY_FUNC_SPEC`, all out-of-class member functions (i.e. those not implemented inside the class or struct declaration) with `BOOST_AFIO_HEADERS_ONLY_MEMFUNC_SPEC`, all virtual member functions with `BOOST_AFIO_HEADERS_ONLY_VIRTUAL_SPEC` and append to all unimplemented virtual member functions  `BOOST_AFIO_HEADERS_ONLY_VIRTUAL_UNDEFINED_SPEC`. This inserts the correct markup to generate both optimal header only and optimal non header only outcomes.
+
+ 2. Precompiled headers:: todo
+
+ 3. extern template pre-instantiated copies of your templates with their most common template parameters into a separate static library:: todo
+
 
 == 16. COUPLING: Consider allowing your library users to dependency inject your dependencies on other libraries ==