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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_extend_srcdir.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_EXTEND_SRCDIR
#
# DESCRIPTION
#
# The AX_EXTEND_SRCDIR macro extends $srcdir by one path component.
#
# As an example, when working in /home/michael/i3-4.12/build and calling
# ../configure, your $srcdir is "..". After calling AX_EXTEND_SRCDIR,
# $srcdir will be set to "../../i3-4.12".
#
# The result of extending $srcdir is that filenames (e.g. in the output of
# the "backtrace" gdb command) will include one more path component of the
# absolute source path. The additional path component makes it easy for
# users to recognize which files belong to the PACKAGE, and -- provided a
# dist tarball was unpacked -- which version of PACKAGE was used.
#
# As an example, in "backtrace", you will see:
#
# #0 main (argc=1, argv=0x7fffffff1fc8) at ../../i3-4.12/src/main.c:187
#
# instead of:
#
# #0 main (argc=1, argv=0x7fffffff1fc8) at ../src/main.c:187
#
# In case your code uses the __FILE__ preprocessor directive to refer to
# the filename of the current source file (e.g. in debug messages), using
# the extended path might be undesirable. For this purpose,
# AX_EXTEND_SRCDIR defines the output variable AX_EXTEND_SRCDIR_CPPFLAGS,
# which can be added to AM_CPPFLAGS in Makefile.am in order to define the
# preprocessor directive STRIPPED__FILE__. As an example, when compiling
# the file "../../i3-4.12/src/main.c", STRIPPED__FILE__ evaluates to
# "main.c".
#
# There are some caveats: When $srcdir is "." (i.e. when ./configure was
# called instead of ../configure in a separate build directory),
# AX_EXTEND_SRCDIR will still extend $srcdir, but the intended effect will
# not be achieved because of the way automake specifies file paths:
# automake defines COMPILE to use "`test -f '$source' || echo
# '\$(srcdir)/'`$source" in order to prefer files in the current directory
# over specifying $srcdir explicitly.
#
# The AX_EXTEND_SRCDIR author is not aware of any way to influence this
# automake behavior. Patches very welcome.
#
# To work around this issue, you can use AX_ENABLE_BUILDDIR i.e. by adding
# the following code to configure.ac:
#
# AX_ENABLE_BUILDDIR
# dnl ...
# AX_EXTEND_SRCDIR
#
# Then also add this bit to Makefile.am (if you wish to use
# STRIPPED__FILE__ in your code):
#
# AM_CPPFLAGS = @AX_EXTEND_SRCDIR_CPPFLAGS@
#
# LICENSE
#
# Copyright (c) 2016 Michael Stapelberg <michael@i3wm.org>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 5
AC_DEFUN([AX_EXTEND_SRCDIR],
[dnl
AS_CASE([$srcdir],
[.|.*|/*],
[
# pwd -P is specified in IEEE 1003.1 from 2004
as_dir=`cd "$srcdir" && pwd -P`
as_base=`AS_BASENAME([$as_dir])`
srcdir=${srcdir}/../${as_base}
AC_SUBST([AX_EXTEND_SRCDIR_CPPFLAGS], ["-DSTRIPPED__FILE__=AS_ESCAPE([\"$$(basename $<)\"])"])
])
])dnl AX_EXTEND_SRCDIR
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