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This macro tries to automatically find the library libmilter.a and the header file "libmilter/mfapi.h", which are required when compiling a milter for Sendmail. When successful, it sets the output variable MILTER_LIBS to "-lmilter", MILTER_LDFLAGS to contain an -Lpathtolib option, and MILTER_CPPFLAGS to contain an -Ipathtoinclude option, if they are necessary.

The easiest way to use this macro is something like:

    AC_MSG_ERROR([required milter library and header not found])

If the macro is successful, it just adds any flags to the necessary environment. If it is not successful, it would likely be a fatal error, because if an application is linking with libmilter.a, it is probably because it is a milter.

There are two optional "–with" options for configure which are added. If they are specified, they override any searching that is done. They are:

   --with-sendmail-base=<DIR>  This option is used to explicitly
         specify the base of the sendmail distribution.
   --with-sendmail-obj=<DIR>   The option is used to explicitly specify
         the "obj.*" subdirectory in the sendmail distribution
         that should be used.

When sendmail-base is not specified, the current environment is first tested to see if the header and library are available, and if so MILTER_LDFLAGS and MILTER_CPPFLAGS are left empty.

There are two places that are searched for the sendmail base directory. The first location is one directory down from the current directory. It checks if there is a directory of the form sendmail-8.1*, limited to version 8.12.x or higher, then chooses the directory with the highest version number. If that method does not succeed, it then looks in the file /etc/mail/ for the directory it was built from, and uses the base of that distribution. If neither of these methods work, then it fails.

There are two methods for finding the "obj.*" directory when it is not specified. The first is to try to run sendmail’s Build program with the -M option which will print out the name of the obj. directory for the tool in the directory where it is run from. If this does not work, is looks for the newest directory of the form "obj.*" in the sendmail base directory.

Two addition output variables that are defined, whether or not the files are found are SENDMAIL_BASE_DIR and SENDMAIL_OBJ_DIR, which are the suspected location of the sendmail base directory and obj.* subdirectory.

NOTE: POSIX threads MUST be configured BEFORE this function is called or it will not find libmilter.a even if it exists. The easiest way is to use the AX_PTHREAD macro by Steven G. Johnson and Alejandro Forero Cuervo which is available from the Autoconf Macro Archive.

Source Code

Download the latest version of ax_path_milter.m4 or browse the macro’s revision history.


Copyright © 2008 Tim Toolan

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

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