Re: BUG (v1.5.6.1): ./configure missing check for zlib.h

On Fri, 27 Jun 2008, tom fogal wrote:

Jakub Narebski [off-list ref] writes:

quoted

Mircea Bardac [off-list ref] writes:

quoted

$ ./configure

[...]

quoted

configure: CHECKS for header files
In file included from daemon.c:1:
cache.h:9:18: error: zlib.h: No such file or directory
make: *** [daemon.o] Error 1

(installing zlib1g-dev on Ubuntu 7.10 fixed the problem)

What should ./configure do (what ./configure for other programs
or packages do)?

You cannot compile git without zlib!

If one can determine during configure time that a required library is
not found, it (IMHO) is nice to give an error message and bomb out (via
AC_MSG_ERROR).

The AC macro archive has a zlib macro which does this, as an example:

   http://autoconf-archive.cryp.to/check_zlib.html

I should note, however, that I disagree with that macro's logic in that
it `searches' for zlib if the user does not specify it.  IMO, if the
user does not give a --with option, and it doesn't work `out of the
box' (without hacking FLAGS), macros should die with an error rather
than retry with changed FLAGS.

On Fri, 27 Jun 2008, Mircea Bardac wrote:

Well, as far as I know, if a program depends on any external headers, 
they should *all* be checked, not only "those that can be skipped by 
defining some macro" (I personally do not know which are these).

In git (not like usually in other projects) ./configure script (autoconf)
is used *only* to generate Makefile configuration.  It tries to configure
compile (build) process in such a way that building git is possible even
if some features are missing or are found not in standard place (and also
use compat version of functions if they are not in library).  It helps you
build system.

I'm not sure if checking if prerequisites exists and failing loudly
otherwise would be a good feature to have.  Git would fail anyway during
build process, so it is not some new feature.  The only advantage is that
required and unavoidable dependency would be found earlier; on the other
hand there is now disadvantage of build process (./configure process)
if it misdetects lack of needed header files, i.e. it is possible to
compile (build) git, but ./configure detects that it is not so.  This
happened once to me, and is very annoying...

But as they say, "code speaks louder than words"

-- 
Jakub Narebski
Poland