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diff --git a/doc/check-version.texi b/doc/check-version.texi new file mode 100644 index 0000000000..f22266b50c --- /dev/null +++ b/doc/check-version.texi @@ -0,0 +1,53 @@ +@node Library version handling +@section Library version handling + +The module @samp{check-version} can be useful when your gnulib +application is a system library. You will typically wrap the call to +the @code{check_version} function through a library API, your library +header file may contain: + +@example +#define STRINGPREP_VERSION "0.5.18" +... + extern const char *stringprep_check_version (const char *req_version); +@end example + +To avoid ELF symbol collisions with other libraries that use the +@samp{check-version} module, add to @file{config.h} through a +AC_DEFINE something like: + +@example +AC_DEFINE(check_version, stringprep_check_version, + [Rename check_version.]) +@end example + +The @code{stringprep_check_version} function will thus be implemented +by the @code{check_version} module. + +There are two uses of the interface. The first is a way to provide +for applications to find out the version number of the library it +uses. The application may contain diagnostic code such as: + +@example + printf ("Stringprep version: header %s library %s", + STRINGPREP_VERSION, + stringprep_check_version (NULL)); +@end example + +Separating the library and header file version can be useful when +searching for version mismatch related problems. + +The second uses is as a rudimentary test of proper library version, by +making sure the application get a library version that is the same, or +newer, than the header file used when building the application. This +doesn't catch all problems, libraries may change backwards incompatibly +in later versions, but enable applications to require a certain +minimum version before it may proceed. + +Typical uses look like: + +@example + /* Check version of libgcrypt. */ + if (!gcry_check_version (GCRYPT_VERSION)) + die ("version mismatch\n"); +@end example |