[avrdude-dev] avrdude and new autotools

[Ville Voipio]

A known problem is that avrdude is not (or at least was not) compileable 
with new autotools. I just bumped into this problem with Ubuntu 7.10 
(and AFAIK, 7.04 and 8.04 will have the same problem). Having several 
versions of autotools installed in the same system seems to be a bit 
awkward, so avrdude should compile with modern versions, as well.

I took a look into this problem (a.k.a @WINDOWS_DIRS@) with automake 
1.10 and autoconf 2.61.

The problem stems from recursive use of variable substitution. Something 
like this (oh, feel free to correct me, I know next to nothing about 
autotools, I just needed to get this fixed):


config.ac:

FOO="this @BAR@"
BAR="is recursive"

AC_SUBST(FOO, $FOO)
AC_SUBST(BAR, $BAR)


makefile.am:

X = @FOO@



Now, if the substitution were recursive, we should have two stepas with X:

X = @FOO@
X = "this @BAR@"
X = "this is recursive"

But as there does not seem to be recursive variable substitution in the 
modern versions, we are left with "this @BAR@" which is certainly not 
what we wanted ("dir @WINDOWS_DIRS@" instead of "dir windows").

I wonder why this worked with autoconf 2.57. Maybe the parser has been 
changed to a single-pass one or something else. Anyway, to avoid nested 
substitutions, this can be overcome by:

config.ac:

FOO="this"
BAR="is not recursive"

AC_SUBST(FOO, $FOO)
AC_SUBST(BAR, $BAR)


makefile.am:

X = @FOO@
X += @BAR@

(Actually, the += operation is reduced away when processing Makefile.am 
into Makefile.)


Another way to go around this is to make the substitution already in 
configure.ac.

Yet another problem I encountered is the lack of AM_PROG_CC_C_O in 
configure.ac.

If these changes sound reasonable, I'll post a patch if someone wants to 
try with older versions.

- Ville