13 Upgrading From Version 1
Autoconf version 2 is mostly backward compatible with version 1.
However, it introduces better ways to do some things, and doesn't
support some of the ugly things in version 1. So, depending on how
sophisticated your `configure.in' files are, you might have to do some
manual work in order to upgrade to version 2. This chapter points out
some problems to watch for when upgrading. Also, perhaps your
`configure' scripts could benefit from some of the new features in
version 2; the changes are summarized in the file `NEWS' in the
First, make sure you have GNU `m4' version 1.1 or higher installed,
preferably 1.3 or higher. Versions before 1.1 have bugs that prevent
them from working with Autoconf version 2. Versions 1.3 and later are
much faster than earlier versions, because as of version 1.3, GNU `m4'
has a more efficient implementation of diversions and can freeze its
internal state in a file that it can read back quickly.
* Changed File Names Files you might rename.
* Changed Makefiles New things to put in `Makefile.in'.
* Changed Macros Macro calls you might replace.
* Invoking autoupdate Replacing old macro names in `configure.in'.
* Changed Results Changes in how to check test results.
* Changed Macro Writing Better ways to write your own macros.
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