As of September 29, 2018 you will find difficulties
on FreeBSD 11.2 running make, as default make is not
gnu-make compatible. The 2018 configure change
to fully use autoconf/automake requires GNU make
to build executables.

========== sh scripts/FIX-CONFIGURE-TIMES
Because git does not record timestamps and sometimes
a copy will lose the timestamps on the build files,
it is usually necessary to
   sh scripts/FIX-CONFIGURE-TIMES
at the top of the source tree before using configure.
See the example scripts below.

========== BUILD PROBLEM SOLUTION: FIX-CONFIGURE-TIMES
Because git does not record timestamps and sometimes
a copy will lose the timestamps on the build files,
the advice here is something you are likely to need
to follow.

From the top-level source do
    sh scripts/FIX-CONFIGURE-TIMES
(before running configure) to fix the important timestamps.
The command is safe to run at any time.
The command checks that it is being run
from an appropriate libdwarf top-level
directory before doing anything.

One clue the script is needed is the following
warning.
"WARNING: 'aclocal-1.15' is missing on your system."

========= End of aclocal issue...
========== CONFUSING BUILD PROBLEM
If you do a full or partial in-source-tree build
(see below) and then attempt an out-of-source-tree
build you will get very confusing messages
about build problems.

Just ensure that the source tree is 'clean'
(as by 'make distclean' or other means)
before you attempt an out-of-source-tree build
(see below for details).

========= End of confusing build problem

========= gcc under MinGW on windows
The configure option --disable-libelf
is no longer needed (but is allowed).

Under MinGW the gcc CFLAGS 
 -DHAVE_WINDOWS_H -DHAVE_NONSTANDARD_PRINTF_64_FORMAT \
 -fno-dwarf2-cfi-asm
have helped some people, though for my MinGW tests
these are not necessary or appropriate.

We have had success with MinGW without setting CFLAGS with (to
save space in this example we do not show checking for errors):
The option --enable-wall is optional.

    src=/path/to/code
    cd $src
    sh scripts/FIX-CONFIGURE-TIMES
    make distclean
    bld=/tmp/dwbld
    rm -rf $bld
    mkdir $bld
    cd $bld
    $src/configure --enable-wall \
      --disable-libelf --enable-nonstandardprintf
    make check
========= End ofgcc under MinGW on windows

========= Standard Builds non-Windows
Standard builds are done by configure/make as described below.
Cross-Compiles are described below, see CROSS COMPILES.
One need not --enable-dwarfgen --enable-dwarfexample.
The option --enable-wall is also optional.

BUILDING in UNIX/Linux
    src=/path/to/code
    cd $src
    sh scripts/FIX-CONFIGURE-TIMES
    make distclean
    bld=/tmp/dwbld
    rm -rf $bld
    mkdir $bld
    cd $bld
    $src/configure --enable-wall --enable-dwarfgen --enable-dwarfexample
    make check
 
BUILDING in MacOS (tried on Catalina)
    Same as linux but as standard the Apple
    Command Line Tools provide no libelf (we don't need it).
    So the final two steps are:
    $src/configure --enable-wall --disable-libelf
    make check
========= End of Standard Builds non-Windows
    

LIBRARY AND HEADER REQUIREMENTS
zlib has to be installed
to handle zlib compressed sections
(common in linux, not normally found with Windows).
in Ubuntu 16.04 and 18.04, install using:
    sudo apt-get install zlib1g zlib1g-dev

zlib is available in source from
    http://zlib.net

libelf is available in source from
    http://www.mr511.de/software/
and
    https://github.com/vtorri/libelf
though libelf is not (as of May 2019)
not needed.


NOTE: When building out of source tree the source tree must
be cleaned of any files created by a build in the source tree
(just in case you tried that) before doing the out-of-source
build. That's whe examples above do a 'make distclean'.

BUILDING ALL THE TOOLS
To build all the tools (including dwarfgen and dwarfexample)
use  a different configure command:
    ./configure --enable-dwarfgen --enable-dwarfexample ; make

To see all the available options to configure do
   ./configure --help

By default configure compiles and uses libdwarf.a.

With
    ./configure --enable-shared
both libdwarf.a and libdwarf.so are built. The runtimes built
will reference libdwarf.so.

With
    ./configure --enable-shared --disable-nonshared
libdwarf.so is built and used; libdwarf.a is not built.

THE USUAL ENVIRONMENT VARIABLES
The following default to sensible values
you may set environment variables as usual
with GNU configure.
CPPFLAGS
CFLAGS
LDFLAGS

DEBUGGING MAKE

To see what compile/link commands are actually
being used by the generated Makefiles try V=1, as in
    make V=1



INSTALL AND UNINSTALL

The default install is to /usr/local

To change the install location use --prefix.
For example:
    mkdir /tmp/testinst
    configure --prefix=/tmp/testinst

So 'make install' (sudo make install) installs into
/usr/local/bin, /usr/local/lib, /usr/local/include, and
/usr/local/share/libdwarf.

Doing 'make uninstall' (sudo make uninstall) deletes
what 'make install' added but does not delete the
/usr/local/share/libdwarf directory that the 'make install'
created.

CHECKING FOR MEMORY CORRUPTION

Recent gcc has some checks that can be done at runtime.
  -fsanitize=address
  -fsanitize=leak
  -fsanitize=undefined
which are turned on here by '<path>/configure --enable-sanitize'.

The --enable-sanitize option unlikely to work when
cross-compiling.

CROSS-COMPILES

For those wishing to build libdwarf (and possibly dwarfdump)
for a different host machine than the build machine
it is now possible to do that.

It has been tested with host and target set to an ARM with
build on X86_64.  See
  https://gcc.gnu.org/onlinedocs/gccint/Configure-Terms.html
for standard GNU usage of build, host, and target.  See also:
  https://www.gnu.org/software/autoconf/manual/\
  autoconf.html#Specifying-Target-Triplets

The autoconf documentation strongly suggests adding --build
to the configure commands and in the example below adding
--build=i686-pc-linux-gnu is known to work on the test machine.

The following is an example. Currently configure figures out
the build environment for itself so we don't use --build here.

On build machine:
sudo apt-get install gcc-arm-linux-gnueabihf
#  Install libelf and zlib (libz) into
#  the gcc cross-build tree too.
#  I cheated: copied from arm machine into
#  gcc-arm-linux-gnueabihf.

mkdir emptycross
cd emptycross
git clone git://git.code.sf.net/p/libdwarf/code
cd code
./configure --host=arm-linux-gnueabihf
make
# done

Doing a build on Ubuntu 18.04 (X86_64 environment)
of a 32-bit libdwarf/dwarfdump requires some care.

Doing
  sudo apt install gcc-6-multilib
helps.

It is a requirement that the build and host machines match
with respect to the existence of system headers
and of libraries.
It seems necessary, in /usr/lib/i386-linux-gnu/ , to 
    sudo cp libelf.so.1 libelf.so
so the linker can find 32-bit libelf.

In addition, one must build zlib for the host
(if you have zlib in the build environment)
(see above for the zlib source link)
with
CFLAGS=-m32 ./configure
make
sudo cp libz.a /usr/lib/i386-linux-gnu/
sudo cp libz.so /usr/lib/i386-linux-gnu/

#building libdwarf/dwarfdump in the source for no good reason:
 ./configure  --host=i386-linux-gnu \
 --build=x86_64-pc-linux-gnu \
 CFLAGS="-O2 -m32" 

------------------ notes on updating ------

To update configure after hand updating a Makefile.am or
the configure.ac do the following command at the top level
(where this file is):
    autoreconf -vif
You will need the autotools installed including autoconf,
automake, and libtool to run autoreconf.

To run the basic checks of libdwarf/dwarfdump, first
do
    ./configure
    make
Then
    make check

A further set of tests is available vi
    sh scripts/buildandreleasetest.sh
which does configure, make check, make install (in
temporary directories), make dist, and cmake.
This script will not work on Windows.

A full set of tests is
   sh scripts/run-all-tests.sh
which requires the regressiontests directory also be
present and if readelfobj is present
will run its 'make check'.
These tests outside the scope of this README.
This script will not work on Windows.

To create a release file on Linux do:
    ./configure --enable-dwarfexample --enable-dwarfgen
    make
    make dist
will generate a libdwarf-yyyymmdd.tar.gz file with the files
needed in a release
    scripts/CPTARTOWEBDIR is an example of generating
fingerprints for the release file and copying the file.

See the configure.ac for the version used.
For example: 'm4_define([v_date], [20190505])])'

David Anderson.  Updated 7 November 2019
