Re: Check for m4

[Eric Blake]

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According to Kamaljit Singh on 12/7/2007 1:04 PM:
> Since autom4te is really a script, should this be something to be deduced
> at the scripts runtime rather than at the install time (using configure) ?

Actually, the converse is true - because autom4te is a script, we want to
fork as few times as possible when autom4te is run, by remembering the
results of expensive tests done at configure time.  Performing a
full-blown PATH check for an acceptable m4 on every invocation of autom4te
is too slow, so we intentionally hard code it to either the environment
variable M4 or what was discovered at configure time.  And as you
discovered, you can override the configured choice by exporting M4, so
it's a livable limitation.

> Seems restrictive, especially because I was hoping to have a single 
> installation
> of the package for both solaris and linux. The autoconf package was configured
> only on linux. This seems to work but for the M4 part, so far.

In general, you can't assume that.  Suppose we were to rewrite portions of
autoconf in C.  Linux and Solaris do not run each other's binary files, so
you cannot install autoconf once and expect it to run on both machines.
In like manner, even though autoconf currently happens to be entirely
composed of interpreted files (perl and shell), the configure process of
autoconf codes in some information specific to the platform where
configure was run, in order to optimize its performance.  Unless you have
identical paths from both operating systems for all things learned by
configure, you are better off running configure twice, once for each
platform you intend to run autoconf on.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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