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Diffstat (limited to 'config_host/README.md')
| -rw-r--r-- | config_host/README.md | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/config_host/README.md b/config_host/README.md new file mode 100644 index 000000000000..af5030460d35 --- /dev/null +++ b/config_host/README.md @@ -0,0 +1,24 @@ +# C/C++ Configuration Created by configure Script + +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` |