amhello with generated version

[Peter Johansson]

Hi,

It has been discussed recently that the way the VERSION is set with 
automake is suboptimal when the VERSION is changing frequently [1]. The 
problem is basically that autoconf has to be re-run every time the 
VERSION is updated, which is not convenient if the VERSION is updated, 
e.g., at every commit to the RVS.

I've played around with a work-around inspired by the git-version-gen 
script in gnulib [2]. Please find a revised version of amhello using the 
idea attached. The idea is, as suggested by by Ralf Wildenhues, to keep 
the version information in a separate file `.version' [3]. Other 
files/targets can then depend on `.version' and propagate the version 
information as appropriate. `.version' is updated from the output of a 
script `gen-version'; here only a wrapper around `date' but could in 
principle be anything from `git describe', `svnversion' to home brewed 
scripts extracting the version from, e.g., ChangeLog. When building from 
a tarball, there exists a file `.tarball-version' and when this file is 
present `.version' will not be updated from the `gen-version' script. 
That is because it is desired that the version is set when the 
maintainer issues `make distcheck' and not at a later point when some 
user builds the package, and also in many situations `gen-version' is 
impossible to run outside the RVS environment, e.g., when the version is 
set by `svnversion'.

Here, the version is propagated to two places: 1) To the hello program, 
which is done by generating a short source file `version.c'. This 
implies when the version changes, only `version.o' needs to be 
re-compiled and version information can be linked into the programs. 2) 
The version is also propagated into the Makefile and in particular so 
the $(distdir) is set accurately. This is done by overriding the 
$(VERSION) variable, and this is done in a file `.version.mk' that is 
included into the Makefile. The file `.version.mk' in turn is generated 
from `.version' and since $(VERSION) is set in a separate file it can be 
updated without re-generating the entire Makefile via config.status.

I chose to have rules for `.version' and `.version.mk' in all Makefiles 
and since they are the same everywhere, I located them in a file 
`version.am' that is included at automake time. The attached tarball is 
obviously not created with `make dist' but what a developer would check 
out from a RVS.

Thoughts or any feedback are very welcome.

Cheers,
Peter

[1]  http://www.mail-archive.com/address@hidden/msg15075.html
[2] 
http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=build-aux/git-version-gen
[3]  http://www.mail-archive.com/address@hidden/msg15121.html

amhello.tar.gz
Description: GNU Zip compressed data