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+These are configuration files for various features as detected by configure.
+
+Include only those files you need (in order to reduce rebuilds when a setting changes).
+
+Settings here are only C/C++ #define directives, so they apply only to C/C++ source,
+not to Makefiles.
+
+
+
+Adding a new setting:
+=====================
+
+- do AC_DEFINE(HAVE_FOO) in configure.ac when a setting should be set
+- choose the proper config_host/config_XXX.h file to use
+ - if it is a global setting (such as availability of a compiler feature),
+ use config_host/config_global.h
+ - otherwise check if there is a matching config_host/config_XXX.h file
+ - if none matches, add a new one:
+ - add config_host/config_XXX.h.in here, with just #ifndef include guard
+ - add AC_CONFIG_HEADERS([config_host/config_XXX.h]) next to the others
+ in configure.ac
+- add #define HAVE_FOO 0 to the config_host/config_XXX.h , possibly with a comment
+ (do not use #undef HAVE_FOO, unless the setting has more values than on/off)
+- add #include <config_XXX.h> before any #if HAVE_FOO in a source file
+- make sure you use #if HAVE_FOO for on/off settings, do not use #ifdef