# ac -- filtered autoconf
#                                      (Master copy is in RHTF directory)
#
#
# The reason for this script is to eliminate an undesirable warning
# message that is familiar to most users of the GNU cross-development
# tools:
#
#     AC_TRY_RUN called without default to allow cross compiling
#
# Background:
#
# #autoconf# and #automake# allow developers to create software that can
# be distributed in source form and run on many different UNIX platforms.
# They automate the creation of the Makefiles, testing for all the
# different flags that have to be set to control which library functions
# are called, what include files exists and where they are located, whether
# ints are big-endian, etc.
#
# Specifically, automake was created to simplify the process of creating
# makefiles. The textbook example Makefiles are very simple, but real
# Makefiles, particularly for anything that has to be distributed to
# many different users using different types of UNIX, are very complicated.
# The complexity comes entirely from dealing with lots of different types
# of UNIX, compilers, etc. automake makes it simple again.
#   Similarly, autoconf simplifies the job of creating the "configure"
# script. "configure" scripts are a common way to solve multi-platform
# issues like figuring out what directory the libraries are in, or whether
# the machine is big-endian. Like Makefiles, configure scripts are
# needlessly large and complicated, and autoconf simplifies things
# dramatically. With automake and autoconf, the developer doesn't have to
# know anything about all the other UNIXs and their idiosyncracies.
#
# The end-product of using automake and autoconf, from the developer's point
# of view, is a "configure" script that, when run by the user, will set up
# the Makefiles to properly build the program on that user's system. When
# it is run, the configure script performs many tests -- finding libraries,
# checking for compiler bugs, etc.
#
# Many of these tests performed by configure involve actually running small
# test programs on the machine where the build is being done. This is what
# AC_TRY_RUN is used for. However, sometimes a user is building not for his
# own machine, but for another; this is called "cross-compiling". An example
# is a user who has an Intel-based Linux system, compiling a program for
# the PalmPilot. In this case, AC_TRY_RUN won't really work because you
# can't easily try little test programs on the PalmPilot when you're
# running on a Linux machine. The warning message shown above tells the
# developer (before he even releases the source code) that this situation
# might cause trouble for the user unless he (the developer) supplies an
# alternative method of testing.
#
# Unfortunately, most developers don't have cross-compiling in mind and
# don't really know any alternative ways of testing. Even if they did,
# they don't know about all the different types of targets (like the
# PalmPilot) that are out there and how to handle each one. Thus, the warning
# message appears and they can't do anything about it, they have no way
# of providing a proper dafault. The message ends up being little more than
# an annoyance.
#
autoconf 2>&1 | grep -v 'warning.*AC_TRY_RUN called without default to allow cross compiling'