perjantai 2. joulukuuta 2016

What does configure actually run

One of the claimed advantages of Autotools is that it depends (paraphrasing here) "only on make + sh". Some people add sed to the list as well. This is a nice talking point, but it is actually true? Lets' find out.

Determining this is simple, we just run the GNU Hello program's configure script under strace like this:

strace -e execve  -f ./configure 2>stderr.txt > stdout.txt

This puts all command invocations of the process and its children to stderr.txt. Then we can massage it slightly with Python and get the following list of commands.

arch
as
basename
bash
cat
cc
cc1
chmod
collect2
conftest
cp
diff
dirname
echo
expr
file
gawk
gcc
getsysinfo
grep
hostinfo
hostname
install
ld
ln
ls
machine
make
mkdir
mktemp
msgfmt
msgmerge
mv
oslevel
print
rm
rmdir
sed
sh
sleep
sort
tr
true
uname
uniq
universe
wc
which
xgettext

This list contains a total of 49 different commands including heavyweights such as diff and gawk.

Thus we find that the answer to the question is no. Configure requires a lot more stuff than just shell plus make. In fact it requires a big chunk of the Unix userland implictly.

Pedantic postscriptum

It could be said that all of these programs are not strictly required and that configure could (potentially) work without them present. This is probably correct, but many of these programs provide functionality which is essential and not provided by either plain shell or Make.

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