Day 16 of 60: I strongly dislike M4

Which is a problem because the Sendmail build system is written in it.

Here's the problem I'm trying to solve.



As mentioned previously, Sendmail supports a DESTDIR variable, which you can set on the make command line, to specify a prefix to be added to the all the installation paths.

The problem is that the build infrastructure doesn't create some necessary directories. Specifically, it won't create:

$DESTDIR/usr/lib
$DESTDIR/usr/bin
$DESTDIR/usr/share/man/cat8
$DESTDIR/usr/share/man/cat5
$DESTDIR/usr/share/man/cat1

Some of the code to support creating this is easy, but I've run in to problem with links.m4.

Specifically, this bit of code:

define(`bldMAKE_TARGET_LINKS',
` for i in $2; do \
rm -f $$i; \
ln -s ${DESTDIR}$1 $$i; \
done'
)dnl

The loop body needs to be modified with a mkdir call, like so:

define(`bldMAKE_TARGET_LINKS',
` for i in $2; do \
-mkdir `dirname $$i`; \
rm -f $$i; \
ln -s ${DESTDIR}$1 $$i; \
done'
)dnl

to ensure that the directory in which the link is going to be created will work.

The problem is the backticks. They don't play nicely with M4. I thought I could fix this with changequote, but this code doesn't work:

dnl Change the quote definition temporarily so that
dnl we can use backticks in the next bit of Makefile
changequote(",")dnl
define("bldMAKE_TARGET_LINKS",
" for i in $2; do \
-mkdir -p `dirname $$i`; \
rm -f $$i; \
ln -s ${DESTDIR}$1 $$i; \
done"
)dnl
dnl Change the quotes back
changequote(, )dnl

More specifically, I get errors like this:

.../library.m4:17 bad macro name

Where library.m4 includes links.m4.

What's especially hateful is that if I cut and paste the code in to a separate m4 file it works fine (read: it produces the correct output).

Anyone know how I might fix this?

PS: Using other characters as quotes (e.g., changequote([, ]) doesn't work, and nor does using $(...) instead of backticks. Solaris' /bin/sh (which make(1) uses) doesn't understand that construct.